Amine-Based Latex Coatings for Indoor Air CO2 Control in

Subscriber access provided by Lancaster University Library

Energy, Environmental, and Catalysis Applications

Amine-Based Latex Coatings for Indoor Air CO2 Control in Commercial Buildings Anirudh Krishnamurthy, Buddhabhushan Salunkhe, Ashish Zore, Ali Rownaghi, Thomas Schuman, and Fateme Rezaei ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b02934 • Publication Date (Web): 11 Apr 2019 Downloaded from http://pubs.acs.org on April 13, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Amine-Based Latex Coatings for Indoor Air CO2 Control in Commercial Buildings Anirudh Krishnamurthy1, Buddhabhushan Salunkhe2, Ashish Zore2, Ali Rownaghi1, Thomas Schuman2, Fateme Rezaei1* 1Department

of Chemical & Biochemical Engineering, Missouri University of Science and Technology, 1101 N State Street, Rolla, MO, 65409, United States 2Department of Chemistry, Missouri University of Science and Technology, 1101 N State Street, Rolla, MO, 65409, United States

Abstract High levels of indoor air CO2 in commercial buildings can lead to various health effects, commonly known as sick building syndrome. Passive control of indoor air CO2 through solid adsorbents incorporated into the paint offers a high potential to handle CO2 without utilizing much energy. This study focuses on incorporating silica supported aminopolymers into a polyacrylic based latex that could be used as a buffer material for passive control of CO2 in enclosed environments. To maximize the effect of the pigment (adsorbent), paints were all prepared at critical pigment volume concentration (CPVC) levels. CO2 at 800 ppm and 3000 ppm were used to asses both low and high level contamination. The removal efficiency of the surface coatings was evaluated within typical time frames (10 h for adsorption and desorption). Our lab-scale chamber results indicated that silica-TEPA based paint with 70 wt% loading exhibits the best adsorption performance, comparable to that of powder-based sorbent, with only a ~20% decrease in adsorption efficiency. Our results also revealed that optimization of paint formulation is critical in passively controlling indoor air CO2. The findings of this study highlight the potential of aminebased adsorbents as pigments in high PVC paints for indoor CO2 control in commercial buildings. Keywords: Indoor air, Latex coating, Aminosilica, CO2 removal, Passive control

1 ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 32

1. Introduction CO2 levels in the indoor environment are an important factor in assessing the safety and viability of a commercial building. The American Society of Heating, Refrigerating and AirConditioning Engineers (ASHRAE) determines that acceptable indoor CO2 levels can be above ~ 500-700 ppm of outdoor concentrations to facilitate a comfortable environment.1 In the U.S., the indoor CO2 concentration in an office environment is anywhere between 100 – 200 ppm above outdoor values (~400 ppm) in presence of good ventilation, according to a study done by Apte et al.2 Higher levels of CO2 are typically found in offices and schools, sometimes as high as 1500 ppm.3,4 Muscatiello et al.5 surveyed different schools in New York state schools and found that CO2 levels were about 800 – 900 ppm on average. This is of particular concern, as children are more vulnerable to indoor pollutants.6 Without adequate ventilation, CO2 can accumulate and lead to a number of negative health effects such as nasal congestion to nausea and headaches.7 CO2 levels in indoor spaces have been found to have profound effects on the performance of the workforce. In a study done by Satish et al.,8 successively higher levels of CO2 at 1000 and 2500 ppm were shown to an adverse effect on different types of activities. Exhalation from human sources have been found to be one of the primary causes of CO2 build up in an enclosed environment, with a CO2 generation rate of 37 g/h per person.1 To control CO2 accumulation, installing and maintaining ventilation systems (HVAC) is the method used presently in accordance with ASHRAE standards.1 As CO2 does not typically reach a steady state concentration in an indoor environment, it is often difficult to determine a ventilation rate that would be adequate. One way to reduce indoor air CO2 concentration and improve indoor air quality in general without increasing the air exchange ventilation rates is development of breathable paints in commercial


Page 3 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


buildings that incorporate CO2 adsorbent materials capable of trapping CO2 during peak hours (daytime) and releasing during nighttime. Passive control of indoor air CO2 through solid sorbents offers a high potential for recovery and is an efficient way to handle CO2 without utilizing much energy. In that regard, metal oxidesupported amines have been shown to have high affinity towards CO2 at low concentration with exceptional selectivity.9–12 This is further enhanced in the presence of moisture, which promotes the formation of amines reacting with CO2 to yield a bicarbonate bond. This makes these materials a good choice in humid environments.13,14 Investigations have been performed on CO2 capture on amine groups mounted on solid materials in the past.15–21 Studies on indoor air quality with respect to CO2 capture has been seldom explored in the past. Cheng and Tan22 attempted to control indoor CO2 concentrations using an aqueous solution monoethanolamine (MEA) or diethylenetriamine (DETA) mixed with piperazine in a rotating packed bed. They were successful in reducing the CO2 concentration from 1000 ppm to 100 ppm over an extended period of time. Jeon et al.23 performed a study on the capture of indoor CO2 using pristine and KOH-modified activated carbon in a custom-made chamber. The authors reported a 500 ppm drop in the overall concentration of CO2 with a maximum adsorption capacity of 3.28 mmol/g for KOH-activated carbon, comparable to amine-based materials. The investigation into the incorporation of solid adsorbents into a latex for CO2 capture has been seldom studied. For instance, Skiles et al.24 developed a design for a photocatalytic film that can be used as a paint/coating for CO2 sequestration. However, the coating involved the conversion of CO2 to non-CO2 based products and was not a passive control method. The film was shown to remove CO2 at a rate of 10 ppm/min at a CO2 concentration of 1 vol. %. In a study conducted by Nomura et al.,25 silica-supported 3-Aminopropyltrimethoxysilane (APS) was formulated into 3 ACS Paragon Plus Environment


Page 4 of 32

polyacrylic-based latex and used for the abatement of formaldehyde. The study revealed the utility of aminosilica materials in the control of indoor pollutants with a low-cost energy scheme. In addition, multiple studies have been performed on the utilization of different systems for the indoor capture of CO2 with the aim of reducing ventilation costs.26,27 With the aim of increasing the efficiency of the existing building system, the sorbent particles can be used as pigments and incorporated into a paint in enclosed spaces, thereby passively capturing pollutants and improving the indoor air quality while reducing ventilation rates. A significant aspect of the preparation of this paint is the concept of ‘critical pigment volume concentration’ or CPVC. The pigment volume concentration, or PVC, is a characteristic in paints that defines its physical properties. It is basically the ratio between the volatiles and non-volatiles in the paint, and will be described further in this paper. The CPVC of a paint is defined as the ratio of the volume of non-volatiles, including the binder, at a point where the volume of the pigment is quantitatively equal to the volume of the binder in the paint with respect to the total volume of the paint mixture, including the binder and is a critical factor to consider when studying and evaluating the nature and performance of coatings and paints.28 At this threshold value, the volume of the pigment is approximately quantitatively equal to the volume of the binder. This also implies that the pigment used is completely in contact with the binder. This introduces interesting qualities in the paint, such as a high porosity and a fairly larger retention of the useable surface area of the pigment used. The exploration of this factor in the development of porous coatings for potential pollutant capture has not been studied before. The disadvantages of using a paint formulation at such high PVC levels, however, are a challenge. For example, brittleness and flaking are two major problems faced. Furthermore, observed in this study, application of such paints seem to result in a relatively non-uniform coating, in that due to the high viscosity of the paint, the bristles of the 4 ACS Paragon Plus Environment

Page 5 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


applicator brush left spaces on the coating surface. In regular paint applications, the PVC is kept very low so as to produce a paint to overcome such problems. Low PVC paints, however, tend to have a lower pigment concentration, which would result in a lower CO2 adsorption efficiency. In our previous work,29 we evaluated the CO2 adsorption and desorption performance of a series of aminosilicates including polyethylenimine (PEI), (3-Aminopropyl)trimethoxysilane (APS) and tetraethylenepentamine (TEPA) with different amine loadings for indoor air CO2 control in commercial buildings. The experiments involved equilibrium and dynamic chamber investigations at room temperature and different levels of humidity. With the aim of experimental significance in the indoor environment, two different types of chamber tests were performed at 1500 and 2100 ppm, which represent higher than ambient concentrations. Dynamic concentration profiles measured for the aminosilica materials revealed the interaction of these materials with CO2 in an indoor environment. Silica-TEPA was found to have relatively higher CO2 uptake, at 1.36 mmol/g measured at 3000 ppm CO2 concentration in equilibrium experiments. Whereas, silica-PEI demonstrated a higher desorption potential. Using the inference obtained from this study, the basis was formed for the selection of the materials for this project. In this investigation, we aimed at incorporating silica-PEI and silica-TEPA with various amine content as pigments into a paint formulation with a polyacrylic-based binder. Various additives such as thickener, film former and preservative were added subsequently to yield a porous paint with a relatively high surface area for the application in smart buildings to reduce ventilation rates and improve indoor air quality by facilitating the adsorption and desorption of CO2. The buffering materials in the powder and latex forms were evaluated in a small-chamber setup using 800 and 3000 ppm CO2 concentrations and two humidity levels (15 and 50% RH). 2. Experimental Section 5 ACS Paragon Plus Environment


2.1.

Page 6 of 32

Synthesis of Amine-Based Latex Coatings

Preparation of Aminosilica Adsorbents. The silica support used in this study was purchased from PQ Corporation (PD-09024). All other chemicals were purchased from Sigma Millipore. The aminopolymers used in the study were TEPA and branched PEI (Mn = 600). The silica support was functionalized by the aminopolymers using the wet impregnation method, as previously described.30 First, the silica was degassed for 24 h at 120 °C to remove any gaseous or volatile impurities. A solution was made using a calculated amount of PEI or TEPA in methanol and was left to stir for 2 h. Immediately after the degassing procedure, silica was added into the above solution and was subsequently left to stir for an additional 12 h to facilitate the impregnation process. To recover the adsorbent from the solution, a rotary evaporator was used after which the impregnated silica powders were subjected to outgassing for 2 h at 80 °C. The final powders obtained were named as silica-PEI and silica-TEPA, with their corresponding impregnated weight percentages. Three variations of each type of adsorbent were prepared, at three different loadings of the aminopolymer. Preparation of Aminosilica-Based Paints. The incorporation of the prepared adsorbents into a paint was achieved in three steps. Cellosize QP 4400 (0.2 wt%) was used as a thickener and was dispersed in a mixture of propylene glycol (2.9 wt%) and water (24 wt%). To maintain a basic pH, AMP 95 (0.3 wt%) was added to the mixture. In next step, canguard 327 (0.2 wt%) and Triton X100 (0.2 wt%) were added while Byk 22 (0.28 wt%) was added shortly after as a defoamer. To further enhance dispersion within the latex mixture, Esperse 100 (2.35 wt%) was used as a dispersant. The mixture was then set to disperse for 30 mins. The prepared aminosilica adsorbents (pigment) were used in quantities according to calculated PVC levels. Typically, calculated values of silica-PEI were added to the mixture in small amounts at 1500 rpm. Due to high PVC levels,


Page 7 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


water was added to achieve homogeneous dispersion and to avoid coagulation. The obtained latex was dispersed for a further 30 mins. Joncryl 1532 (32.7 wt%) was used an emulsion and was added to the above dispersion at 1000 rpm, with the successive addition of Ucar IBT (1 wt%) which was added as a film former. A white aminosilica slurry was obtained with a very high viscosity. This paint was then coated using a standard paint brush onto a glass sheet of 10 cm diameter with a film thickness of 55 microns and left to dry for 48 h at 50 °C. The final paints obtained were named as PEI(y)-L and TEPA(y)-L, where y refers to the mass percentage of impregnated aminopolymers on the silica support. Three variations of each type of adsorbent were prepared, at three different loading percentages of the aminopolymer. The calculated aminopolymer loading in the final prepared paints, namely, PEI20-L, PEI35-L, PEI50-L and TEPA35-L, TEPA60-L, TEPA70-L were 20, 30 and 40 wt% respectively, for each class of material in the final paint formulation. 2.2.

Characterization of Amine-Based Latex Coatings To assess the textural properties of the coatings, N2 physisorption isotherms were obtained

using a Micromeritics 3Flex gas analyzer at 77 K. Degassing in a Micromeritics Prevac was performed for 1 h at 110 °C. Surface area was consequently determined using Brunauer-EmmettTeller (BET) while pore volume was estimated using the BJH desorption method, obtained from the same device. Fourier-transform infrared spectroscopy (FT-IR) measurements were measured on a Nicolet Nexus 470 optical bench to determine the functional groups in the adsorbent coatings. Oil adsorption (OA) was used as a parameter to calculate the CPVC of the prepared paints using the standard ASTM D281 method. In this study, the oil absorption tests were performed using a 50 mL burette filled with the binder/emulsion. A large glass sheet was placed under the burette loaded with the adsorbent under investigation. The binder was allowed to contact the adsorbent dropwise. The adsorbent and binder were then thoroughly mixed until a waxy substance 7 ACS Paragon Plus Environment


Page 8 of 32

is obtained. This indicated the saturation of the binder in the adsorbent. The volume of oil absorbed onto the adsorbent, Voil , was recorded to be used in eq. 1. The steps were then repeated multiple times to get an average value. The total time of the experiment was also kept constant at about 20 min.

OA 

(OA f  Voil ) WP

(1)

The oil absorption value was calculated using eq. 1, where OA is the oil absorption capacity (mL), OA f is the oil factor (100 g), Voil is the volume of oil absorbed from the burette (mL) and WP is

the weight of the pigment selected (g). The critical pigment volume concentration was calculated using eq. 2. CPVC  1

1 100 (OA)  p

(2)

(100   B )

In eq. 2,  p is the density of the pigment (g/cm3) and  B is the density of the binder used for the test (g/cm3). 2.3.

CO2 Adsorption Chamber Experiments The CO2 adsorption characteristics of the prepared materials were investigated using a set-

up similar to our previous work25, as depicted in Figure 1. The set-up consisted of a small 10 L stainless-steel chamber connected to a CO2 analyzer (AEMC instruments, Indoor Air Quality meter 1510) at the outlet, which was placed inside an insulated environment to maintain operating conditions. CO2 concentrations in the inlet were maintained at 800 and 3000 ppm respectively, to evaluate low and high levels of CO2 contamination in the indoor environment. The CO2 feed flow rate during adsorption step was set to 90 mL/min. an air flow. An air flow with a flow rate of 400 8 ACS Paragon Plus Environment

Page 9 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


mL/min was used in the case of 800 ppm to dilute the source cylinder. During desorption, only air was used as a feed gas to regenerate the adsorbents at ambient temperature. A 10 cm circular glass sheet was placed within the chamber on which the paint was applied. The lining of this chamber was covered in Teflon sheets to eliminate any wall interactions. This was done to simulate indoor conditions. Before each run, a bypass was performed to determine the inlet concentration of CO2 from ambient air. The concentration was allowed to equilibrate for one hour before the flow rate was turned off to stabilize CO2 concentrations at the indoor environment for a further hour. This was done to obtain fairly stable levels of outdoor CO2 and to apply some significance to the experiment, as regular working hours occur around this time. Outdoor CO2 levels were recorded to be between 425 - 435 ppm. The elevation in CO2 concentration level as compared to measured ambient concentrations could have been attributed to increased pollution levels present at that time of the day. Due to relative humidity (RH) being an influential parameter in the adsorption of pollutants onto amines along with being a fundamental parameter in the determination of indoor air quality solutions, a saturator containing distilled water was supplied as the source of relative humidity into the chamber using the ambient air as the carrier gas. Low and high levels of RH were studied at 15% and 50%, respectively while temperature and pressure were maintained at ambient conditions.



Page 10 of 32

Figure 1. Chamber set-up used to determine CO2 uptake over latex coatings.

The aminosilica powder-based adsorbent was sprinkled onto the glass sheet using a sieve, as illustrated by Figure 2a. A fairly even distribution of the adsorbent along the surface of the glass sheet was obtained to accurately examine CO2 capture efficiency and to compare it with its corresponding paint. Similarly, the paints were coated onto the glass sheets using a brush. The weight of the paint on the glass sheet was kept constant in its wet state. This resulted in fairly consistent film weights in its dry state. Due to the high viscosity of the paint, the standard procedure of settling of the film did not occur, and we had bristle marks across the area of the glass sheet, as shown in Figure 2b. This is a consequence of using a high PVC level paint, and showed a similar pattern with all the paints that were coated. The weight of the aminosilica adsorbent (i.e. pigment) was maintained at 0.4 g corresponding to 2.0 g of latex coating. Once CO2 levels were fairly constant, the inlet flow of CO2 was sent into the chamber to investigate CO2 adsorption performance of the materials to be tested for a duration of 7 h.


Page 11 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Desorption, via concentration swing of the materials was performed by continuing the air flow rate for 3 h. A total time frame of 10 h was selected to simulate a typical working day.

Figure 2. (a) Silica-TEPA 70 powder sprinkled (b) TEPA70-L coated onto the glass sheet used for CO2 chamber tests. CO2 adsorption capacity was calculated using eq. 3:

qd 

QCO2 CCO2 tads

(3)

22.4Wads

Where qd is the adsorption capacity (mmol/g), QCO2 is the inlet flow rate of CO2 (mL/min), CCO2 is the inlet concentration of CO2 (ppm), tads is the time required for adsorption (min) and Wads is the weight of adsorbent used in the experiment. In case of the paint samples, the weight of the film was used in estimation of qd. 3. Results and Discussions The oil absorption (OA) is an indicator of what quantity of the pigment (e.g. aminosilica particles) can be added to the paint formulation without suffering the disadvantages of a high PVC paint, which can result in flaking and brittle film formation while maintaining a high pigment volume concentration to provide porosity to the applied film. Using the OA capacity estimated 11 ACS Paragon Plus Environment


from eq. 1, CPVC values of the respective paints were calculated and are summarized in Figure 3. An inverse dependence between OA capacity and CPVC was observed, indicating the potential for larger pigment loading with lower OA values. TEPA-L samples exhibited a lower CPVC as compared to PEI-L latexes. This could be attributed to the nature of the interaction between the binder and the pigment, as this information implies that a larger amount of pigment can be dispersed in a smaller amount of binder for PEI when compared to TEPA. Notably, the CPVC of the paints did not vary much with the increase in aminosilica loading. 160

OA CPVC

148 140 120 100 80 61

60 40 25

31

58 36

90

85

81 58 36

37

35

34

20

70 PA TE

TE PA 60

PA 35 TE

I5 0 PE

I3 5 PE

PE I2 0

ca

0

Si li

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 32

Figure 3. Relation between OA capacity and CPVC for aminosilica-based paints.

Table 1 depicts the coating properties of the prepared paints. All paint properties were calculated in the dry state of the coating. The weight of the coating was maintained at 3 g in the wet state on application. The aminosilica content was calculated by eq. 4, where WAS was the weight of the aminosilica in the paint in its dry state (g) and W film was the weight of the coated film in its dry state (g).


Page 13 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


AS (%) 

WAS 100 W film

(4)

Similarly, the amine percentage present in the coatings were calculated from eq. 5.  A  WAS A(%)   %  W film 

  100 

(5)

In the above equation, A% represents the amine impregnation percentage (%), which was obtained from the initial material synthesis procedure. As shown, the aminosilica content was similar for each class of material. Moreover, higher leaching of the amine groups was observed in the case of silica-TEPA when compared to silica-PEI, thus, the initial amount of TEPA used for impregnation was higher than that for PEI. This could be due to the greater bonding achieved by the branched PEI with a larger number of amine groups (8) when compared to the TEPA (5). This suggested a greater degree of interaction between the binder and the aminosilica pigment in the case of PEI, which was reflective of its lower OA capacity and subsequently, higher CPVC. The weight of the film on the glass sheet was kept fairly consistent, and due to the similarity in CPVC with each class of material, consequently, the same amount of aminosilica was loaded onto the glass sheet. This was done to determine the relation between amine loading and CO2 capture capacity. Table 1. Properties of aminosilica-incorporated coated films. Sample PEI20-L PEI35-L PEI50-L TEPA35-L TEPA60-L TEPA70-L

Weight of dry film (g) 0.39 0.40 0.40 0.39 0.41 0.40

Aminosilica content (wt%) 76.9 77.2 77.6 51.3 51.6 51.7

Amine content (wt%) 19 27 40 17 29 39

Latex content (wt%) 23.1 22.8 22.4 49.7 49.4 49.3

3.1. Characteristics of Amine-Based Latex Coatings 13 ACS Paragon Plus Environment


The N2 physorption isotherms and pore size distribution profiles of the aminosilicaincorporated latex coatings are displayed in Figure 4. To perform the measurpoement, the film was carefully scraped from the glass sheet and transferred to the apparatus. The results indicated a type IV shape,31 with a hysterisis loop ranging from P/P0 = 0.5 – 0.9, which illustrated the uniformity of the mesopores in the paints32 and mesoporus nature of the coatings. Notably, the N2 uptakes over coating samples were comparable to those of corresponding aminosilica adsorbents (see Figure S1, Supporting Information), suggesting a retention of surface characteristics after latex incorporation. Furthermore, in agreement with the powder analogues, N2 uptake decreased upon increasing amine content for both PEI and TEPA-based latex coatings.

200

0.04 0.03 0.02 0.01 0.00 10

150

20

30

Pore Diameter (nm)

PEI20-L PEI35-L PEI50-L

100 50

200

150

dV/dD Pore Volume (cm³/g·nm)

250

250

Quantity Adsorbed (cm³/g STP)

dV/dD Pore Volume (cm³/g·nm)

300

0.05

(b)

0.06

(a)

0.06

350

Quantity Adsorbed (cm³/g STP)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 32

0.05

0.04

0.03

0.02

0.01

0.00

100

0

5

10

15

20

Pore Diameter (nm)

TEPA35-L TEPA60-L TEPA70-L

50

0

0 0.0

0.2

0.4

0.6

0.8

1.0

0.0

Relative Pressure (P/P0)

0.2

0.4

0.6

0.8

1.0

Relative Pressure (P/P0)

Figure 4. N2 physisorption isotherms for (a) PEI and (b) TEPA based paints.

On comparison with the powder sorbents, the pore volume of the paints was shown to decrease. This could be explained by the interference of latex particles within the pore system of the sorbents. Keeping PVC levels above CPVC, the interference of heavier, non-porous components such as the binder was kept to a minimum, while the relatively porous pigment 14 ACS Paragon Plus Environment

Page 15 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


material suffered only a small decrease in pore volumes. The corresponding textural properties of the latex adsorbents presented in Table 2 revealed a decreasing trend in pore volume and surface area with amine content, in accordance with the powder samples (Table S1, Supporting Information). Also, minimal loss in surface characteristics of the latex paints was compared in comparison to the powders, indicating the successful incorporation of the powder based sorbents into the latex formulation. TEPA70-L, the highest aminopolymer loading paint exhibited a SBET of 24 m2/g and a Vp of 0.10 cm3/g which was a drastic decrease from TEPA35-L, with an SBET of 123 m2/g and 0.50 cm3/g.

Table 2. Surface characteristics of amine-based latex coatings. Sample PD-silica PEI20-L PEI35-L PEI50-L TEPA35-L TEPA60-L TEPA70-L

SBET (m2/g)

Vp (cm3/g)

dp (nm)

294 136 129 51 123 93 24

1.04 0.52 0.47 0.23 0.50 0.20 0.10

10.1 11.8 11.6 11.0 11.8 11.6 11.3

The morphology of the bare latex and aminosilica (TEPA-based) incorporated latex samples are illustrated in Figure 5. To obtain these SEM images, the paints were gently applied to the glass sheet and after the appropriate drying time, the thin film was carefully removed. Whereas the bare latex displayed a smooth surface (Figure 5a), the rough surfaces were observed after addition of the pigments (Figure 5b-d). This was due to a high PVC level, which covered the latex film, as opposed to low PVC paints, which have larger portions of exposed latex and do not yield a tight packing of the paint molecules. Moreover, due to similar aminosilica content for TEPA35-L, 15 ACS Paragon Plus Environment


Page 16 of 32

TEPA60-L, and TEPA70-L (Table 1), the surface morphology of these samples appeared to be quite similar. These images confirm the successful incorporation of the aminopolymers into the latex coating. It should be noted that a similar morphology was observed for the PEI-based coatings.

Figure 5. SEM images of (a) bare latex, (b) TEPA35-L, (c) TEPA60-L, and (d) TEPA70-L.

The corresponding EDS spectra of TEPA- and PEI-based paints are presented in Figure 6. When comparing the bare latex material to the paint formulated, a sharp rise in Si spectrum detection was observed and the peak intensity increased with higher loadings as a result of subsequent lower content in other elements detected.


Page 17 of 32

Si

Si

(a) C

C O

TEPA60-L

TEPA35-L

(b)

O

PEI50-L

Intensity (a.u.)

TEPA70-L

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


PEI35-L

PEI20-L

Bare latex

Bare latex 0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0

0.5

Energy (keV)

1.0

1.5

2.0

2.5

3.0

Energy (keV)

Figure 6. EDS spectra of (a) TEPA-based paints and (b) PEI-based paints.

The dispersion of Si in the latex was confirmed by the elemental mapping, presented in Figure 7b for the case of TEPA70-L. Also, the Si content was shown to be dispersed through the periphery of the latex for all other paints formulated (see Figure S2, Supporting Information). While nitrogen cannot be accurately determined using this technique due to limitations for low valance elements,33 from Figure 7c, we observed a dispersion of N through the aminopolymer loaded paints in contrast to the bare latex through elemental mapping, illustrated by Figure 7f, which showed very minor detections stemming from the additives used in the formulation.



Page 18 of 32

Figure 7. Elemental mapping of (a-c) TEPA70-L and (d-f) bare latex.

To further demonstrate the incorporation of aminosilica particles into the latex coating, FTIR spectra were collected and compared with that of bare latex for both TEPA- and PEI-based coatings, as shown in Figure 8. Two prominent peaks were detected in the paints at 1080 cm-1, which corresponded to Si-O stretching, while a small peak at approximately 800 cm-1 was stemmed form Si-O-Si stretching vibration.34 This was shown to be much stronger in the case of the TEPA samples, as depicted in Figure 8a. The peak in the 1300 cm-1 range signifies the polyethylene portion of the material,35 which was detected in all materials, as polyethylene based-compounds can be found in the latex formulation. Furthermore, as evident from Figure 8a, the intensity of the C-N bands increased with increased loading, indicating a higher amine concentration in the paints. The functionalization of the amine moieties onto the aminosilica materials can be illustrated by the secondary peaks obtained at around 1000 – 1200 cm-1, which correspond to C-N stretching in aliphatic amines. This confirms that the PEI remains fairly undamaged after latex incorporation. Furthermore, as evident from Figure 8b, the intensity of the C-N bands increased with increased 18 ACS Paragon Plus Environment

Page 19 of 32

loading, indicating a higher amine concentration in the paints. The higher loaded samples also show another band at around 1650 cm-1, which is due to the symmetric N-H bending from primary amine groups.36 N-H vibrational mode was also detected at about 900 cm-1, indicative of primary and secondary amine groups. These bands were not detected in the bare latex, and signifies the successful incorporation of the amine groups onto the paint. As the CPVC level of TEPA is much lower than that of PEI, a consequently lower intensity of Si related bonds was detected. Notably, the N-H wagging movements were also not detected. Minor bands were detected around 3700 cm-1 which were observed due to the hydroxyl groups present in the support silica material.37 What was noticeable was the suppression of this band after the amine impregnation, when compared to the bare latex, which suggested the formation of amine-silanol complexes. This suppression is higher in TEPA samples when compared to PEI, which could also be the reason for a weaker C-N band detected earlier.38 C-H

Bare latex TEPA35-L TEPA60-L TEPA70-L

(a)

PEI20-L PEI35-L PEI50-L

Si-O N-H C-N

1000

N-H

1500

(b)

Bare latex

Absorbance (%)

Absorbance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2000

2500

3000

3500

C-H

Si-O

C-N N-H

1000

1500

-1

Wavenumber (cm )

2000

2500

3000

3500

-1

Wavenumber (cm )

Figure 8. FTIR spectra for (a) TEPA- and (b) PEI-based paints.

3.2. Chamber CO2 Experiments



Page 20 of 32

Figure 9 illustrates the CO2 breakthrough results obtained from the chamber tests using 800 ppm CO2/air at 15% RH for all paints prepared. The corresponding chamber test results for the powder sorbents can be found in the Figure S3, Supporting Information, under the same conditions. In a time frame of 10 h, complete saturation of the adsorption and desorption was observed for the coatings. The effectiveness of the aminosilica latex coatings in passively controlling CO2 could be realized by the reduction in CO2 level in chamber air compared to bare latex case, and also by gradual raise in CO2 concentration as opposed to sharp increase in the case of bare latex (Figure 9a,c). For instance, while for empty chamber (blank run) the CO2 concentration reached its maximum (~850 ppm) within 1 h, it took 4 h for chamber with TEPA70L to reach its maxim value (~760 ppm). It should be noted that the tail end of the figures depicts the desorption of the CO2. It is inferred that the physically adsorbed species appreciably desorbs in the assigned time frame (3 h). While the desorption process is fairly quick (e.g. 2 h for TEPA70L), the adsorption process was much longer (e.g. 4 h for TEPA70-L). This delay in desorption could be due to strong adsorption efficiency of the amines to CO2 which would explain why this phenomenon is observed in both powder and paint samples. Figure 9b,d represent the calculated adsorption capacities for TEPA and PEI-based materials, respectively. Further investigation of these chamber test results revealed that silicaTEPA-latex materials were shown to have a much better CO2 capture efficiency when compared to silica-PEI latex, as reported before.16 The most efficient capture was achieved by TEPA70-L at 1 mmol/g. Similarly, PEI50-L was observed to have the best adsorption capacity at 0.5 mmol/g among silica-PEI samples. However, unlike their powder counterparts, the difference in capture efficiencies between the PEI50-L and TEPA70-L was close to 50%. To test the effects of the


Page 21 of 32

support and binder, bare silica and bare latex were also tested, and showed minimal capture capacities.

Blank Bare latex TEPA35-L TEPA60-L TEPA70-L

700

Adsorption Capacity (mmol/g)

CO2 concentration (ppm)

1.6

(a)

800

600

500

(b)

0

2

4

6

8

10

12

1

1.0

0.6 0.4

0.5 0.3

0.28

0.2

0.1

0.0

1.0

700

Adsorption capacity (mmol/g)

Blank run Bare latex PEI20-L PEI35-L PEI50-L

600

500

1

0.8

0.8

Bare silica/Latex

(c)

1.3

1.2

Time (hr)

800

Powder samples Paint samples

1.4

400

CO2 concentration (ppm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(d)

TEPA35

TEPA60

Powder samples

TEPA70

0.9

Paint samples 0.8

0.6

0.6

0.5

0.5 0.4

0.4

0.28 0.2

0.2

0.1

400 0

2

4

6

Time (hr)

8

10

12

0.0

Bare silica/Latex

PEI20

PEI35

PEI50

Figure 9. Small chamber tests at 800 ppm and 15% RH for (a) TEPA-based paints, (b) corresponding calculated CO2 uptake for paints (solid) and powder sorbents (shaded), (c) PEIbased paints, and (d) corresponding calculated CO2 uptake for paints (solid) and powder sorbents (shaded).

To determine any changes to the stability of the aminosilica-latexes, we performed three adsorption-desorption cycles and investigated their capacity over consecutive cycles. Figure 10 illustrates cyclic tests performed on TEPA70-L at 800 ppm and 15% RH. Fractional loss in capacity during cyclic runs after purging with the air stream during the desorption process suggests 21 ACS Paragon Plus Environment


that physisorption is more dominant than chemisorption during this phenomenon. A 7.5% reduction in capacity was detected from the fresh run to the first cycle, with subsequent cycle displaying a very low reduction in uptake, revealing the reusability of the prepared paints. These tests prove that aminosilica based paints at high PVC levels are promising candidates for passive control of indoor air CO2 in commercial buildings. 850

Fresh run

Recycle 1

Recycle 2

1.2

(a)

800 1.0

750

Adsorption capacity (mmol/g)

CO2 Concentration (ppm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 32

700 650 600 550 500 450 400 0

8

16

Time (h)

24

32

(b) 1

0.93

0.92

Recycle 1

Recycle 2

0.8

0.6

0.4

0.2

0.0 Fresh run

Figure 10. (a) Cyclic runs for TEPA70-L and (b) estimated adsorption capacities obtained at 800 ppm and 15% RH.

Due to the role of relative humidity in the indoor environment, the materials were tested at elevated relative humidity levels (RH = 50%), which is higher than ambient conditions, as mentioned earlier. As demonstrated in Figure 11, the RH level had a negative effect on the adsorption capacity of bare silica/latex, and caused a decrease in CO2 uptake, whereas for aminebased latex adsorbents, the capture capacity enhanced at higher RH level. For example, under the same CO2 concentration, an enhancement of up to 30% was observed at 50% RH compared to 15% RH (Figure 9). These results are in accordance with our previous investigations and other studies performed on similar materials,29,36 where the increase in humidity level facilitates a greater


Page 23 of 32

amine capture potential. Notably, the desorption time and rate were increased when compared to lower humidity level which is attributed to the higher CO2 capture capacity of amine-based materials at humid conditions. The lower desorption rates can be particularly identified in the powder samples, where the powder samples were shown to have incomplete desorption in the time frame provided. Investigation of the CO2 chamber results revealed the drop in capacity of the aminosilica materials after incorporation into the latex coatings. Such behavior could be correlated to the reduction in amine sites as a results of partial pore blockage or amine leaching during paint preparation. The reduction in capacities from powder to latex samples for 800 ppm CO2 and 15% RH are detailed in Figure S4, Supporting Information. Increase in amine loading generally resulted in less reduction in capacities for both classes of materials, with the exception of TEPA60 and TEPA70. The largest reduction was observed for the lowest loaded samples, which could be due to the leaching of amine groups during the paint processing. Higher concentration of amine groups resulted in more retention. This was additionally observed in Table 1, where higher loading percentages resulted in higher amine retention. (a)

Blank Bare latex TEPA35-L TEPA60-L TEPA70-L

800

700



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


600

500

400 0

2

4

6

Time (hr)

8

10

12

2.0

(b)


1.6

1.5

1.5

1.3 1.1 1.0

0.7 0.5

0.4 0.2

0.1

0.0 Bare silica/Latex TEPA35

TEPA60

TEPA70


850


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(c)




800 750 700 650 600 550 500 450 0

2

4

6

Time (hr)

8

10

12

1.0

Page 24 of 32


(d)

0.8

1

0.72

0.66

0.65

0.6

0.36

0.4

0.2

0.42

0.2 0.1

0.0

Bare silica/Latex

PEI20

PEI35

PEI 50


In the next step, we examined the effect of CO2 level in indoor air under two humidity levels (15 and 50%) by conducting chamber tests at a CO2 inlet concentration of 3000 ppm and the results are displayed in Figure 12. Larger quantities of CO2 resulted in larger saturation times, which increased the total duration of the cycle to 13 h. The results indicated that upon increase in CO2 concentration from 800 to 3000 ppm, the CO2 uptake over coatings increased, in agreement with the powder counterparts. The highest adsorption capacity among the powder samples was obtained from TEPA70, similar to the previous case, at 1.6 mmol/g. The loss in CO2 uptake was found to be more pronounced for TEPA35, as was the case for 800 ppm runs, primarily due to amine leaching (from 20 to 17%, see Table 1). The loss in capacity with the incorporation of the powder into the latex for TEPA70 was found to be around 20%. This was similar to the drop in capacity experienced in the 800 ppm runs. The chamber tests for the powder sorbents can be found in the supporting information (Figure S5, Supporting Information). All adsorbents and paints showed complete desorption within the time frame selected for the experiment. Higher amine loaded samples, however, showed slower rates of desorption when compared to lower loaded samples. 24 ACS Paragon Plus Environment

Page 25 of 32

TEPA based samples also showed slower rates of desorption when compared to PEI materials, which was to be expected due to the superior adsorption of the TEPA adsorbents and paints, as inferred before. Additionally, we investigated the effect of indoor air humidity by performing the chamber tests with an inlet concentration of 3000 ppm of CO2 with elevated relative humidity levels, at 50%. As Figure S6 (Supporting Information) illustrates, we observed the same positive effect trend on CO2 uptake at higher RH levels. These results indicated that at higher concentrations, the aminosilica-incorporated coatings could potentially be efficient in situations with higher consistent CO2 exposure such as crowded enclosed spaces with high levels of humidity. The 3000 ppm takes about 6 – 7 h to reach saturation, which in contrast to 3 h in the case of 800 ppm at the same humidity level. (a)

1.6

Blank run Bare latex TEPA35-L TEPA60-L TEPA70-L

2500


3000


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2000

1500

1000

500 0

2

4

6

8

Time (hr)

10

12

14

16

(b)


1.4 1.2

1.33 1.1

1.0

1

0.9

0.8

0.6

0.6 0.4 0.2

0.36

0.3 0.1

0.0 Bare silica/Latex TEPA35

TEPA60

TEPA70



(c)

1.2


2500


3000


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

2000

1500

1000

(d)

Page 26 of 32

Powder samples

1.1

Paint samples

1.0

0.8

0.8 0.7 0.6

0.6

0.5 0.4 0.3 0.2

0.2 0.1

500 0

2

4

6

8

Time (hr)

10

12

14

16

0.0 Bare silica/Latex

PEI20

PEI35

PEI50


As a control experiment, we prepared bare aminopolymer latex films (with no silica particles) with the 40 wt% amine content and tested them at 800 and 3000 ppm under 15% RH. The corresponding chamber test results are illustrated by Figure S7. The results revealed that the CO2 concentration level decreased by a much smaller magnitude than the aminosilica films. Furthermore, the film had strong amine based olfactory properties, which could potentially limit the utility of these films. CO2 concentrations were found to decrease similar to the trend followed by the aminosilica based materials, where TEPA based film performed marginally better than PEI based films. Furthermore, the aminopolymer was largely undispersed within the formulation, which also effected the distribution of active sites through the extent of the film. This was due to the immiscibility between the aminopolymer and the latex formulation. All capacities were calculated to be around the capacity of the bare latex, at around 0.1 mmol/g.


Page 27 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4. Conclusion This investigation was a successive step to our previous work to determine the efficacy of aminosilica based materials for CO2 abatement in the indoor environment. TEPA and PEI were successfully impregnated onto a mesoporous silica support and were consequently incorporated with a polyacrylic based latex at CPVC level, to obtain a paint formula with high surface qualities. The most efficient paint was found to be TEPA70-L with an adsorption capacity of 1.0 mmol/g at 800 ppm of CO2 and 15% RH. The effects of relative humidity and CO2 concentration on control of CO2 concentration in indoor air were evaluated and the results obtained indicated the enhancement in performance of latex coatings at elevated humidity and CO2 levels. PEI based paints were shown to have a high reduction in capacity after latex incorporation. High shear forces used to prepare the paints could be responsible for the leaching of the amine groups, and thereby yielding a lesser uptake capacity. Higher amine loadings and larger volumes with lower shear rates could potentially solve this issue. Cyclic runs were also carried out to determine the reusability of these paints, and negligible reduction in capacities were detected. This suggests that these paints can be used repeatedly without a large efficiency loss. This investigation proves that the incorporation of aminosilica materials into paint formulations can be potentially used as a passive CO2 control technology, greatly reducing energy demands in frequented, enclosed spaces, such as office rooms or school classrooms. Supporting Information N2 physisorption isotherms and pore size distribution profiles for powder materials, elemental mapping of Si dispersion on latexes, chamber test results for powder adsorbents, reduction of adsorption capacity from powder to latex samples, and additional CO2 results for latex coatings at 3000 ppm and 50% RH. 27 ACS Paragon Plus Environment


Page 28 of 32

Author Information Corresponding Author *Email: [email protected] ORCID Fateme Rezaei: 0000-0002-4214-4235 Notes The authors declare no competing financial interest.

Acknowledgement Financial support from Missouri S&T’s Smart Living Signature Area and National Science Foundation (NSF CBET-1549736) is acknowledged. The authors would also thanks Dr. Glenn Morrison for his guidance and providing the experimental setup to perform chamber tests. Shane Lawson is acknowledged for helping with SEM/EDS images.

References (1)

Stanke, D. A.; Danks, R. A.; Muller, C. O.; Hedrick, R. L.; Fisher, F. J.; Osborn, J. E.; Butler, D. S.; Gallo, F. M.; Rasmussen, R. D.; Alevantis, L. E.; Girman, John R Rogers, Lisa J Schoen, Lawrence J Bellenger, Lynn G Houston, Thomas P Howard, Eli P Sheinman, Harris M Howard, Roger L Siano, Dennis M Macmillan, Don Spata, Anthony J Marbery, Carl A Damiano, Leonard A Woodford, Michael W Kennedy, Stephen D Marriott, Carol E. Ventilation for Acceptable Indoor Air Quality. ASHRAE Stand. 2010, 2007 (STANDARD 62.1), 1–70. https://doi.org/ISSN 1041-2336.

(2)

Apte, M. G.; Fisk, W. J.; Daisey, J. M. Associations Between Indoor CO2 Concentrations and Sick Building Syndrome Symptoms in U.S. Office Buildings: An Analysis of the 1994 – 1996 BASE Study Data. Indoor Air 2000, 10, 246–257.

(3)

Gall, E. T.; Nazaroff, W. W. New Directions: Potential Climate and Productivity Benefits from CO2 Capture in Commercial Buildings. Atmos. Environ. 2015, 103, 378–380. https://doi.org/10.1016/j.atmosenv.2015.01.004. 28 ACS Paragon Plus Environment

Page 29 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(4)

Annesi-Maesano, I.; Baiz, N.; Banerjee, S.; Rudnai, P.; Rive, S. Indoor Air Quality and Sources in Schools and Related Health Effects. J. Toxicol. Environ. Heal. - Part B Crit. Rev. 2013, 16 (8), 491–550. https://doi.org/10.1080/10937404.2013.853609.

(5)

Muscatiello, N.; Mccarthy, A.; Kielb, C.; Hsu, W. H.; Hwang, S. A.; Lin, S. Classroom Conditions and CO2 Concentrations and Teacher Health Symptom Reporting in 10 New York State Schools. Indoor Air 2015, 25 (2), 157–167. https://doi.org/10.1111/ina.12136.

(6)

Luu, I.; Brown, G. Indoor Air Quality Assessment of Campus Spaces with Carbon Dioxide (CO2) as a Measure of Adverse Health Effects. 2015, 1–9.

(7)

Seppanen, O. A.; Fisk, W. J.; Mendell, M. J. Association of Ventilation Rates and CO2 Concentrations with Health AndOther Responses in Commercial and Institutional Buildings. Indoor Air 1999, 9 (4), 226–252. https://doi.org/10.1111/j.16000668.1999.00003.x.

(8)

Satish, U.; Mendell, M. J.; Shekhar, K.; Hotchi, T.; Sullivan, D. Concentrations on Human Decision-Making Performance. 2012, 120 (12), 1671–1678.

(9)

Gebald, C.; Wurzbacher, J. A.; Borgschulte, A.; Zimmermann, T.; Steinfeld, A. SingleComponent and Binary CO2 and H2O Adsorption of Amine-Functionalized Cellulose. Environ. Sci. Technol. 2014, 48 (4), 2497–2504. https://doi.org/10.1021/es404430g.

(10)

Kishor, R.; Ghoshal, A. K. Amine-Modified Mesoporous Silica for CO2 Adsorption: The Role of Structural Parameters. Ind. Eng. Chem. Res. 2017, 56 (20), 6078–6087. https://doi.org/10.1021/acs.iecr.7b00890.

(11)

Hicks, J.C.; Drese, J.H.; Fauth, D.J.; Gray, M.L.; Genggeng Qi, G.; Jones C.W. Designing Adsorbents for CO2 Capture from Flue Gas-Hyperbranched Aminosilicas Capable of Capturing CO2 Reversibly. J. Am. Chem. Soc., 2008, 130 (10), 2902–2903

(12)

Didas, S. A.; Kulkarni, A. R.; Sholl, D. S.; Jones, C. W. Role of Amine Structure on Carbon Dioxide Adsorption from Ultradilute Gas Streams Such as Ambient Air. ChemSusChem 2012, 5, 2058–2064. https://doi.org/10.1002/cssc.201200196.

(13)

Kumar, A.; Madden, D. G.; Lusi, M.; Chen, K. J.; Daniels, E. A.; Curtin, T.; Perry, J. J.; Zaworotko, M. J. Direct Air Capture of CO2 by Physisorbent Materials. Angew. Chemie Int. Ed. 2015, 54 (48), 14372–14377. https://doi.org/10.1002/anie.201506952.

(14)

Shen, X.; Du, H.; Mullins, R. H.; Kommalapati, R. R. Polyethylenimine Applications in Carbon Dioxide Capture and Separation: From Theoretical Study to Experimental Work. Energy Technol. 2017, 5 (6), 822–833. https://doi.org/10.1002/ente.201600694.

(15)

Choi, S.; Gray, M. L.; Jones, C. W. Amine-Tethered Solid Adsorbents Coupling High Adsorption Capacity and Regenerability for CO2 Capture from Ambient Air. ChemSusChem 2011, 4 (5), 628–635. https://doi.org/10.1002/cssc.201000355.

(16)

Thakkar, H.; Eastman, S.; Al-Mamoori, A.; Hajari, A.; Rownaghi, A. A.; Rezaei, F. Formulation of Aminosilica Adsorbents into 3D-Printed Monoliths and Evaluation of Their CO2 Capture Performance. ACS Appl. Mater. Interfaces 2017, 9 (8), 7489–7498. https://doi.org/10.1021/acsami.6b16732. 29 ACS Paragon Plus Environment


Page 30 of 32

(17)

Liu, S.-H.; Lin, Y.-C.; Chien, Y.-C.; Hyu, H.-R. Adsorption of CO2 from Flue Gas Streams by a Highly Efficient and Stable Aminosilica Adsorbent. J. Air Waste Manage. Assoc. 2011, 61 (2), 226–233. https://doi.org/10.3155/1047-3289.61.2.226.

(18)

Linneen, N. N.; Pfeffer, R.; Lin, Y. S. Amine Distribution and Carbon Dioxide Sorption Performance of Amine Coated Silica Aerogel Sorbents: Effect of Synthesis Methods. Ind. Eng. Chem. Res. 2013, 52 (41), 14671–14679. https://doi.org/10.1021/ie401559u.

(19)

Qi, G.; Wang, Y.; Estevez, L.; Duan, X.; Anako, N.; Park, A.-H. A.; Li, W.; Jones, C. W.; Giannelis, E. P. High Efficiency Nanocomposite Sorbents for CO2 Capture Based on Amine-Functionalized Mesoporous Capsules. Energy Environ. Sci. 2011, 4 (2), 444–452. https://doi.org/10.1039/C0EE00213E.

(20)

Kuwahara, Y.; Kang, D. Y.; Copeland, J. R.; Bollini, P.; Sievers, C.; Kamegawa, T.; Yamashita, H.; Jones, C. W. Enhanced CO2 Adsorption over Polymeric Amines Supported on Heteroatom-Incorporated SBA-15 Silica: Impact of Heteroatom Type and Loading on Sorbent Structure and Adsorption Performance. Chem. - A Eur. J. 2012, 18 (52), 16649–16664. https://doi.org/10.1002/chem.201203144.

(21)

Heydari-Gorji, A.; Belmabkhout, Y.; Sayari, A. Polyethylenimine-Impregnated Mesoporous Silica: Effect of Amine Loading and Surface Alkyl Chains on CO2 Adsorption. Langmuir 2011, 27 (20), 12411–12416. https://doi.org/10.1021/la202972t.

(22)

Cheng, H. H.; Tan, C. S. Removal of CO2 from Indoor Air by Alkanolamine in a Rotating Packed Bed. Sep. Purif. Technol. 2011, 82 (1), 156–166. https://doi.org/10.1016/j.seppur.2011.09.004.

(23)

Jeon, D.-H.; Bae, S.-T.; Park, S.-J. Preparation and Characterization of Chemically Activated Carbon Materials for CO2 Capture. Carbon Lett. 2016, 17 (1), 85–89. https://doi.org/10.5714/CL.2016.17.1.085.

(24)

Davis, C. D.; Us, P. A.; Askin, A. L.; Burrell, L. US 7,910,220 B2, 2011.

(25)

Nomura, A.; Jones, C. W. Amine-Functionalized Porous Silicas as Adsorbents for Aldehyde Abatement. ACS Appl. Mater. Interfaces 2013, 5, 5569–5577.

(26)

Leibundgut, H.; Piatkowski, N.; Baldini, L.; Wurzbacher, J. A.; Kim, M. K. A Novel Ventilation Strategy with CO2 Capture Device and Energy Saving in Buildings. Energy Build. 2014, 87, 134–141. https://doi.org/10.1016/j.enbuild.2014.11.017.

(27)

Kim, M. K.; Leibundgut, H. Performance of Novel Ventilation Strategy for Capturing CO2 with Scheduled Occupancy Diversity and Infiltration Rate. Build. Environ. 2015, 89, 318–326. https://doi.org/10.1016/j.buildenv.2015.02.012.

(28)

Bierwagen, G. P.; Rich, D. C. The Critical Pigment Volume Concentration in Latex Coatings. Prog. Org. Coatings 1983, 11 (4), 339–352. https://doi.org/10.1016/00330655(83)85007-9.

(29)

Rajan, P. E.; Krishnamurthy, A.; Morrison, G.; Rezaei, F. Advanced Buffer Materials for Indoor Air CO2 Control in Commercial Buildings. Indoor Air 2017, No. March, 1–11. https://doi.org/10.1111/ina.12386. 30 ACS Paragon Plus Environment

Page 31 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(30)

Rezaei, F.; Jones, C. W. Stability of Supported Amine Adsorbents to SO2 and NOx in Postcombustion CO2 Capture. 1. Single-Component Adsorption. Ind. Eng. Chem. Res. 2013, 52 (34), 12192–12201. https://doi.org/10.1021/ie4019116.

(31)

Khalfaoui, M.; Knani, S.; Hachicha, M. A.; Lamine, A. Ben. New Theoretical Expressions for the Five Adsorption Type Isotherms Classified by BET Based on Statistical Physics Treatment. J. Colloid Interface Sci. 2003, 263 (2), 350–356. https://doi.org/10.1016/S0021-9797(03)00139-5.

(32)

Liu, Y.; Dai, H.; Deng, J.; Xie, S.; Yang, H.; Tan, W.; Han, W.; Jiang, Y.; Guo, G. Mesoporous Co3O4-Supported Gold Nanocatalysts: Highly Active for the Oxidation of Carbon Monoxide, Benzene, Toluene, and o-Xylene. J. Catal. 2014, 309, 408–418. https://doi.org/10.1016/j.jcat.2013.10.019.

(33)

Gazulla, M. F.; Rodrigo, M.; Blasco, E.; Orduña, M. Nitrogen Determination by SEMEDS and Elemental Analysis. 2013, No. April, 394–401. https://doi.org/10.1002/xrs.2490.

(34)

Nomura, A.; Jones, C. W. Airborne Aldehyde Abatement by Latex Coatings Containing Amine-Functionalized Porous Silicas. Ind. Eng. Chem. Res. 2015, 54 (1), 263–271. https://doi.org/10.1021/ie504165d.

(35)

Gulmine, J. V.; Janissek, P. R.; Heise, H. M.; Akcelrud, L. Polyethylene Characterization by FTIR. Polym. Test. 2002, 21 (5), 557–563. https://doi.org/10.1016/S01429418(01)00124-6.

(36)

Liu, S. H.; Wu, C. H.; Lee, H. K.; Liu, S. Bin. Highly Stable Amine-Modified Mesoporous Silica Materials for Efficient CO2 Capture. Top. Catal. 2010, 53 (3–4), 210– 217. https://doi.org/10.1007/s11244-009-9413-z.

(37)

Krishnamurthy, A.; Thakkar, H.; Rownaghi, A. A.; Rezaei, F. Adsorptive Removal of Formaldehyde from Air Using Mixed-Metal Oxides. Ind. Eng. Chem. Res. 2018, 57, 12916–12925. https://doi.org/10.1021/acs.iecr.8b02962.

(38)

Yu, J.; Le, Y.; Cheng, B. Fabrication and CO2 Adsorption Performance of Bimodal Porous Silica Hollow Spheres with Amine-Modified Surfaces. RSC Adv. 2012, 2 (17), 6784–6791. https://doi.org/10.1039/c2ra21017g.



Graphical Abstract

ACS Paragon Plus Environment

Page 32 of 32

Amine-Based Latex Coatings for Indoor Air CO2 Control in

Recommend Documents