Production of Yellow Iron Oxide Pigments by Integration of the Air

Jan 7, 2014 - Copyright © 2014 American Chemical Society .... submersible pumps (22) (AP1000, Guangdong Zhenhua Electrical Appliance Co., Ltd., China...
0 downloads 0 Views 2MB Size
Download PDF
Article pubs.acs.org/IECR

Production of Yellow Iron Oxide Pigments by Integration of the Air Oxidation Process with Bipolar Membrane Electrodialysis Xu Zhang, Xiaolin Wang, Yaoming Wang, Chuanrun Li, Hongyan Feng, and Tongwen Xu* CAS Key Laboratory of Soft Matter Chemistry, Laboratory of Functional Membranes, School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China S Supporting Information *

ABSTRACT: To resolve problems with the traditional air oxidation process for producing yellow iron oxide pigments, an integration of bipolar membrane electrodialysis (BMED) with the air oxidation process was proposed. Before the integration, both the individual air oxidation process and the BMED process were investigated. The matching conditions for the integration were found to be as follows: pH = 2.5−2.8, FeSO4 concentration = 50−75 g FeSO4·7H2O/L, current density = 60 mA/cm2, distilled water flow rate = 0.3 L/h, etc., under which all the products generated were qualified as the same as those of the individual production process. In addition, economic evaluation of the integration was conducted. Even though the process cost is not as low as expected, it can achieve “zero waste discharge” because the produced inorganic base can be directly used in the air oxidation process and the cogenerated acid can be used in pickling industries. In conclusion, the integration is a feasible, effective, and environmentally friendly process. Equation 1 is the same as eq 3, in that α-FeOOH, which is gradually generated in the reaction, is deposited on the surface of the seed crystals. When the byproduct (H2SO4) concentration increases to a certain level, the reaction reaches an equilibrium and stops. To allow the reaction to proceed toward the right and accelerate the growth of crystals, the byproduct (H2SO4) should be neutralized.1 For the Penniman-zoph process, metallic iron is added to react with H2SO4 (eq 2), and the FeSO4 generated can serve as a raw material for eq 1 while for the air oxidation process, alkaline reagents, such as NaOH, NH3·H2O, etc., are added to neutralize the H2SO4 (eq 4). With the price of metallic iron growing higher, the Penniman-zoph process has become more expensive and will be gradually discontinued in the future. With regard to the air oxidation process, generally the raw material (FeSO4) is obtained during the pickling of steel sheets or the production of titanium dioxide by the sulfate process,6,7 which can reduce the cost to a large extent. Meanwhile, the wastewaters from the above two processes are disposed effectively. Even so, two problems still exist for the air oxidation process: one is that the addition of alkaline reagents will increase the cost; the other is that the final waste liquor (inorganic salt solution in eq 4: Na2SO4, (NH3)2SO4, etc.) will be a burden for environmental and economic efficiency. Bipolar membrane electrodialysis (BMED) is electrodialysis integrated with bipolar membranes, which can split water into OH− and H+ at their interfaces under reverse bias in a direct current field.8 When applied to convert organic or inorganic salt, BMED can realize self-production of H+ and OH− in situ without introducing any other chemical reagents and secondary

1. INTRODUCTION Yellow iron oxide pigment has a composition of α-FeOOH and the structure of goethite, and it has long been used as a coloring material, known popularly as goethite, loess, and ocher. Because of the special weather resistance, strong tinting strength, chemical stability, and low cost, yellow iron oxide pigment has been used to color paints, inks, rubber, and plastic as well. Also, because it is free from toxicity, further applications include coloration of cosmetics, roll papers for tobacco filters, chicken feed, etc. At the same time, it is the raw material for producing red iron oxide pigments, black iron oxide pigments, magnetic iron oxide, and industrial catalysts.1,2 So the demand for yellow iron oxide pigments is growing conspicuously. The traditional production processes for yellow iron oxide pigments include the aniline process, the precipitation process, the Pennimanzoph process, the air oxidation process, etc.1,3−5 Among these processes, the Penniman-zoph process and the air oxidation process are used more frequently than others; both of them include two crucial steps: the seed crystal preparation and the growth. The seed crystal preparations are the same while the seed crystal growth processes are different. For the Pennimanzoph process, the seed crystal growth steps are described in eqs 1 and 2: 4FeSO4 + O2 + 6H 2O = 4α‐FeOOH + 4H 2SO4

(1)

Fe + H 2SO4 = FeSO4 + H 2

(2)

while for the air oxidation process, the seed crystal growth steps are illustrated in eqs 3 and 4: 4FeSO4 + O2 + 6H 2O = 4α‐FeOOH + 4H 2SO4

(3)

H 2SO4 + 2NaOH = Na 2SO4 + 2H 2O

(4)

Received: Revised: Accepted: Published:

In eq 4, the base (NaOH) can also be replaced by Na2CO3, NH3·H2O, etc., and the byproducts are formed accordingly. © 2014 American Chemical Society

1580

November 13, 2013 December 16, 2013 January 7, 2014 January 7, 2014 dx.doi.org/10.1021/ie403847a | Ind. Eng. Chem. Res. 2014, 53, 1580−1587

Industrial & Engineering Chemistry Research

Article

salt pollution.9,10 Because this process is technically advanced, energy efficient, and environmentally benign, it has atracted much attention and has been applied or investigated in chemical syntheses, food processing, organic and inorganic acid regeneration, environmental protection, etc.11−15 In allusion to the features of the air oxidation process and BMED, an integration of them may resolve the problems with the traditional air oxidation process and create unique effects: (i) BMED can convert the final waste liquor (inorganic salt) into inorganic acid and base, (ii) the inorganic base can be used to neutralize the extra acid solution generated in the air oxidation process; (iii) the inorganic acid can be applied in pickling industries. Hence, on the basis of these, it can be speculated that fresh alkaline reagents will be not needed, and a production model of “zero waste discharge” can be achieved. Therefore, the aim of this study is to investigate the feasibility of such integration for producing yellow iron oxide pigments. The individual air oxidation process and the individual BMED process as well as their integration would be investigated, respectively. In addition, economic evaluation of the integrated production process would be conducted.

2. EXPERIMENTAL SECTION 2.1. Materials. All the chemicals used in this study were of analytical grade, purchased from a domestic chemical reagents company. Distilled water was used throughout the study. 2.2. Experimental Setup. 2.2.1. Setup for the Air Oxidation Process. Figure 1a shows the individual experimental setup diagram for the air oxidation process. The volume of the reaction tank (1) is about 10 L (diameter = 150 mm, height = 570 mm). The air compressor (8) (Shanghai Fugrand Mechanical & Electrical Co., Ltd., China) provides aeration by the air distributor (9) placed on the bottom of the reaction tank (1). The solution temperature in the reaction tank (1) is controlled by the automatic programming temperature controller (4) (Henan Aibote Science and Technology Development Co., Ltd., China), heater band (3), and temperature sensing electrode (6). The solution pH is monitored and controlled by the pH control cabinet (2) (Shanghai Shiyuan Bioengineering Equipment Co., Ltd., China), pH electrode (10) (InPro 3030/225, Mettler-Toledo, Switzerland), and base tank (5). The peristaltic pump (12) used to pump the solution from a tank (11) to the reaction tank (1) is supplied by Baoding Longer Precision Pump Co., Ltd., China. Before the experiment, the reaction tank (1) was filled with 2.4 L of seed crystals and 5.6 L of water, and the seed crystals were provided by Tongling Rely Technology Co., Ltd., China. Tank 5 was filled with about 1.0 mol/L NaOH solution, and tank 11 was filled with saturated FeSO4 solution. To ensure normal growth of the yellow iron oxide pigments crystals, some extra conditions were set according to the preliminary experiments: (I) the FeSO4 concentration in reaction tank 1 was 50−75 g FeSO4·7H2O/L; (II) the pH in reaction tank 1 was kept between 2.5 and 2.8; (III) within the initial 24 h, the aeration rate was 200 L/h, and after 24 h, the aeration rate was constant at 300 L/h; (IV) the heating curve of the automatic programming temperature controller is shown in Figure S1 (see Supporting Information); (V) the base concentration in base tank 5 was constant at around 1 mol/ L. After 50 h, the yellow iron oxide pigments crystals in reaction tank 1 were analyzed at a preset time interval. 2.2.2. Setup for BMED. The BMED setup is illustrated in Figure 1b. The setup comprises the following sections: (a) DC

Figure 1. The schematic diagram of experimental setups. (a) Setup for the air oxidation process; (b) setup for the BMED process; (c) integrated experimental setup. (1) Reaction tank; (2) pH control cabinet; (3) heater band; (4) automatic programming temperature controller; (5) base tank; (6) temperature sensing electrode; (7) flow meter; (8) air compressor; (9) air distributor; (10) pH electrode; (11) FeSO4 solution tank; (12) peristaltic pump; (13) BMED membrane stack; (14) DC power supply; (15−21) tanks.

power supply (14) (WYJ-100 V/10A, Shanghai Querli Electronic Equipment Co., Ltd., China); (b) tanks (15−21) and submersible pumps (22) (AP1000, Guangdong Zhenhua Electrical Appliance Co., Ltd., China, with a maximum flow rate of 400 L/h) to store and circulate the relative solutions; (c) peristaltic pump (12) (Baoding Longer Precision Pump Co., Ltd., China) to regulate the flow rate of the water feed; (d) BMED membrane stack (13). The membrane stack contains two electrode compartments, eight base compartments, eight acid compartments, and eight salt compartments. Compartments were separated by cation/bipolar/anion membranes, plastic partition nets (thickness ≈ 1.0 mm), and silicone gaskets 1581

dx.doi.org/10.1021/ie403847a | Ind. Eng. Chem. Res. 2014, 53, 1580−1587

Industrial & Engineering Chemistry Research

Article

(thickness ≈ 0.8 mm). The main characteristics of the ion exchange membranes used in the BMED stack are listed in Table 1. The effective area of each membrane is 40 cm2. The

t

E=

Table 1. Main Characteristics of the Ion Exchange Membrane Used in the Experimentsa JAM-II-05

JCM-II-05

BPM-I

thickness (mm) IEC (meq·g−1)

0.16−0.23 1.8−1.2

0.16−0.23 2.0−2.9

voltage drop (V) water content (%) area resistance (Ω·cm2) transport number voltage drop (V)

−

−

0.16−0.23 positive side: 1.4−1.8 negative side: 0.7−1.1 0.9−1.8

24−30

35−43

35−40

4−8

1−3

−

0.90−0.95

0.95−0.99

−

−

−

0.9−1.8

t

∫0 CtQ dt

(5)

where Ut is the voltage drop across the BMED stack at time t, I is the current applied, Ct is the NaOH concentration in base tank,and Q is the flow rate of feeding water from tank 21 to tank 19.

membrane type properties

∫0 UIt dt

3. RESULTS AND DISCUSSION 3.1. Air Oxidation Process. The individual air oxidation process to produce yellow iron oxide pigments was investigated through three independent parallel experiments. Figure 2 depicts the change in trend of the aeration rate, temperature, pH, and FeSO4·7H2O concentration over time during the process. Figure 2a confirms that the aeration rate is 200 L/h within the initial 24 h and is then constant at 300 L/h after 24 h. Figure 2b demonstrates that the experimental heating curve is in good agreement with the setting one. Figure 2c,d illustrates that the pH value and FeSO4·7H2O concentration are controlled appropriately. Figure 3 depicts the total base consumption during the process, and it is easy to find that the base consumption is small during the first 24 h, suggesting that the reaction rate is much slower during that time; subsequently, the reaction rate becomes fast and the base consumption increases quickly with time. The total reaction equation for producing yellow iron oxide pigments can be obtained by summing eqs 3 and eq 4 (c.f., eq 6).

a

The data were supplied by Beijing Tingrun Membrane Technology Development Co., Ltd., China.

electrodes are made of titanium coated with ruthenium. Tanks 15, 16, 17, 18, and 19 were the anode solution tank, cathode solution tank, acid solution tank, salt solution tank, and base solution tank, respectively. Na2SO4 solution (0.3 mol/L, 1 L) was used as a rinse for tank 15 and tank 16, tank 17 was filled with a dilute H2SO4 solution (0.1 mol/L, 1 L), tank 18 was filled with Na2SO4 solution (1 mol/L, 2 L), and NaOH solution (1 mol/L, 1.5 L) was added to tank 19. The distilled water in tank 21 was pumped into tank 19 at a fixed flow rate continuously, at the same time the base solution of a certain concentration was discharged from tank 19 by overflowing, and tank 20 was used to receive the base solution. During the operation, samples from the acid tank and base tank were analyzed at predetermined time intervals, respectively. 2.2.3. Integrated Experimental Setup. Compared with the individual setups for the air oxidation process and BMED process, the main difference in the integrated experimental setup (shown in Figure 1c) is that tank 5 in Figure 1a is replaced with tank 20 in Figure 1b to control the pH in Figure 1c, while others are fixed. During the integrated operation process, all the operating conditions for producing the yellow iron oxide pigments are the same as those in the individual air oxidation process. Because the base consumption is small during the initial 24 h in the individual air oxidation process, the BMED setup was not run until the air oxidation process ran for 24 h. Besides these, some changes were also made to BMED in this section: tank 18 was full of Na2SO4 solution (1.25 mol/ L, 10 L) that was the final waste liquor of the air oxidation process, and tank 17 was filled with dilute H2SO4 solution (0.1 mol/L, 3 L). 2.3. Analyses and Data Calculations. The properties of the yellow iron oxide pigments crystals were determined by Tongling Rely Technology Co., Ltd., China. The concentration of H+ was analyzed by titration with a standard NaOH solution with phenolphthalein as an indicator. The concentration of OH− was analyzed by titration with a standard HCl solution with methyl orange as an indicator. The total energy consumption E (kWh/(mol NaOH)) was calculated as eq 5:

4FeSO4 + O2 + 8NaOH = 4α‐FeOOH + 4Na 2SO4 + 2H 2O

(6)

Also as shown in Figure 3, the expression of the base consumption rate (i.e., chemical reaction rate of eq 6) can be obtained. First, quadratic equations were selected to fit the three curves (as illustrated in Table 2), and the value of correlation coefficients indicates that the fitting results are satisfactory. Second, taking the derivative of the three equations, the equation of the chemical reaction rate can be expressed as follows. r=

dnNaOH = at + b V dt

(7)

where r is the chemical reaction rate (mol/(L·h)), t is the reaction time (h), V is the volume of reaction solution (L), and nNaOH is the quantity of the base consumption (mol). a and b are two constants, and as seen from Table 2, a is a positive value while b is a negative one. The chemical reaction rate increases with time. The reasons for this may include the following: (1) Over time, the reaction temperature increases, resulting in an increase in the chemical reaction rate. (2) Within the initial 24 h, the aeration rate is 200 L/h, and after that time, the aeration rate is 1.5 times higher than 200 L/h. (3) The yellow iron oxide pigment crystals grow quickly over time, thus providing a larger reaction interface. In addition, as seen from the three curves in Figure 3, when the operation time is about 70 h, the base and FeSO4·7H2O consumption is about 0.45 and 1.53 kg, respectively, and 0.49 kg of product (α-FeOOH) is generated correspondingly. The data can serve as a reference for the BMED process. The quality of the product (α-FeOOH) is shown in Table 3 together with that of standard products. All the parameters of 1582

dx.doi.org/10.1021/ie403847a | Ind. Eng. Chem. Res. 2014, 53, 1580−1587

Industrial & Engineering Chemistry Research

Article

Figure 2. The change in trend of the (a) aeration rate, (b) temperature, (c) pH, and (d) FeSO4·7H2O concentration over time during the individual air oxidation process.

Table 2. Fitting Results of the Base Consumption Curves for the Individual Air Oxidation Process item 1st group 2nd group 3rd group

quadratic equation n = 2.60 1.62 × n = 2.70 1.92 × n = 2.30 2.35 ×

× 10−3t2 − 10−2t × 10−3t2 − 10−2t × 10−3t2 − 10−2t

correlation coefficient (R2) 0.9887 0.9905 0.9897

reaction rate equation r = 6.50 × 10−4t − 2.03 × 10−3 r = 6.75 × 10−4t − 2.40 × 10−3 r = 5.75 × 10−4t − 2.94 × 10−3

3.2. BMED Process. As stated in section 3.1, during the individual air oxidation process, the base consumption rate increased with time, and about 0.45 kg of NaOH was consumed during 70 h. Also, in section 2.2.1, it is required that the base concentration be around 1.0 mol/L. So for the individual BMED process, there are three critical items that should be considered carefully: (1) The base production rate of the BMED process should be not be less than the base consumption rate of the air oxidation process. (2) The quantity of the base produced by the BMED process should meet the requirement of the base consumption of the air oxidation process. (3) The concentration of the base produced by the

Figure 3. The base concentration changes over time during the individual air oxidation process.

the three products are not only up to the industrial standard but also up to the primary standard. 1583

dx.doi.org/10.1021/ie403847a | Ind. Eng. Chem. Res. 2014, 53, 1580−1587

Industrial & Engineering Chemistry Research

Article

Table 3. Quality Comparison between Standard Products and Experimental Products by the Individual Air Oxidation Processa primary standard industrial standard product I product II product III a

volatile matter at 105 °C (%)

hydrotrope (%)

residue on sieve

iron content (%)

pH

≤1.00 ≤1.00 0.77 0.89 0.85

≤0.40 ≤0.40 0.34 0.36 0.36

≤0.10 ≤0.40 0.09 0.07 0.08

≥86.00 ≥86.00 88.24 87.36 88.35

3.5−7.0 3.5−7.0 5.5 5.2 5.7

appearance yellow yellow yellow yellow yellow

powder powder powder powder powder

The results are supplied by Tongling Rely Technology Co., Ltd., China.

BMED process should be around 1.0 mol/L. In addition, in this section, an operation time of 10 h was chosen to investigate the stability of the BMED process, and if stability is confirmed, the operation model can be used in the subsequent integrated production process for the yellow iron oxide pigments. First, considering the base consumption rate, the flow rate of the distilled water pumped to the base tank was set to 0.3 L/h, an appropriate value based on preliminary tests. Second, when other factors were fixed, the effect of the operating current density on the BMED performance was investigated. Figure 4

Figure 5. The concentration changes in base tank and acid tank at different current densities over time during the individual BMED process.

Figure 4. The voltage drop−time change at different current densities during the individual BMED process.

be speculated that the base concentration will continue to decrease over time, and some steps should be taken to prevent that from happening. Taking the case of 60 mA/cm2 as an example, we adopted two modified methods for the BMED process. The first one is duly adding some solid base into the salt tank to neutralize the protons that diffused from the acid tank (called “modified 1”), and the second one is removing some acid from the acid tank when the acid concentration is high (called “modified 2”). Figure 6 depicts the voltage drop−time change of the two cases together with the case of “not-modified”. Similar to Figure 4,

shows the voltage drop−time change at different current densities. Voltage drops change over time inconspicuously, the voltage drop at 70 mA/cm2 is higher than that at 50 or 60 mA/ cm2, and the voltage drop at 50 mA/cm2 is close to that at 60 mA/cm2. As derived from the energy consumption data, E70 > E60 > E50. The concentration changes in the base tank and acid tank under different current densities are shown in Figure 5. First of all, there is no doubt that the higher the current density, the higher the acid concentration and base concentration. Second, from the left part of Figure 5, the three curves show that the base concentrations decrease with time after 6 h. Possible explanations are as follows: (1) As time goes by, the acid concentration increases quickly because of concentration diffusion, imperfect permselectivity of the anion exchange membrane, and the effect of electric field. The protons may diffuse from the acid tank to salt tank and then further transport through the cation exchange membrane to neutralize some hydroxide ions in base tank. (2) Because of the imperfect permselectivity of the cation exchange membrane, hydroxide ions will migrate from the base tank to salt tank under the electric field. On the basis of these analyses, in summary, it can

Figure 6. The voltage drop−time change of the three cases (“notmodified”, “modified 1”, “modified 2”) during the individual BMED process. 1584

dx.doi.org/10.1021/ie403847a | Ind. Eng. Chem. Res. 2014, 53, 1580−1587

Industrial & Engineering Chemistry Research

Article

voltage drops follow the order “modified 2” > “modified 1” > “not-modified”, and the energy consumption of “modified 1” is the smallest among the three, possibly because the total base production quantity of “modified 1” is the largest. The concentration changes in the salt tank, base tank, and acid tank of the three cases are illustrated in Figure 7, respectively.

Figure 8. The BMED voltage drop changes over time during the integrated production process.

Figure 7. The concentration changes in the salt tank, base tank, and acid tank of the three cases (“not-modified”, “modified 1”, “modified 2”) over time during the individual BMED process.

In the left part, the acid concentration in the salt tank of “notmodified” is higher than that of “modified 1” and “modified 2″, and especially the concentration of “modified 1” is the lowest, possible because the base concentration of “modified 1” is constant at around 1.0 mol/L and will not decrease all the time. Also, in the middle part, the base concentration of “modified 2” is higher than that of “not-modified”, but its concentration will still decrease in the final several hours, so “modified 2” is less effective than “modified 1”. The right part of the figure shows that the acid concentration in the acid tank will be decreased by adopting “modified 1”, possible because the hydroxide ions from the solid base migrate to the acid tank to neutralize some protons in the acid tank under the electric field. In summary, “modified 1” is more effective than “modified 2”, but “modified 1” will consume additional solid base. So the two methods should be taken into overall consideration (when the acid concentration in salt tank is high, “modified 1” is adopted; when the acid concentration in acid tank is high, “modified 2” is adopted) in the following integrated production process. 3.3. Integration of the Air Oxidation Process with BMED. As stated in section 2.2.3, during the integrated production process, the BMED setup did not work until the air oxidation process ran for 24 h. Two parallel integrated experiments were operated in this case. The change in trend of aeration rate, temperature, pH, and FeSO4·7H2O concentration over time of the integrated production process is illustrated in Figure S2 (see Supporting Information). Similar to Figure 2, the four items of the two groups are all up to standard. Figure 8 shows the changes in BMED voltage drops over time. On the whole, the voltage drops are relatively stable, and the energy consumption is about 0.5 kWh/(mol NaOH). The concentrations in the acid tank and base tank are depicted in Figure 9. From the left part of the figure, the acid concentrations show a wavy trend because “modified 2” was adopted in the BMED process; from the right part of the figure, the base concentrations are stable at about 1 mol/L, so it meets the requirement of base concentration in the

Figure 9. The concentration changes in the base tank and acid tank of BMED over time during the integrated production process.

air oxidation process. Table 4 shows the quality comparisons between standard products and experimental products; both of the experimental products are up to the industrial standard and primary standard. 3.4. Preliminary Economic Evaluation. The experimental results confirm the feasibility of producing iron yellow pigments by the integrated production process in both technique and product quality. Nevertheless, the economic viability should also be considered. Comparing the individual air oxidation process and the integrated production process, the main economic difference focuses on the BMED process section. So the economic evaluation of the BMED process can directly indicate whether the integrated production process is economical or not. The cost of the BMED process section was calculated by the procedure as reported in the literature,16−18 and Table 5 shows the results. As seen from Table 5, the total process cost of producing base with the individual BMED process is estimated to be 1.70 $/kg NaOH, and this price is slightly high. The main cause may be the relatively low current efficiency (41.71%) when compared with other BMED processes (current efficiency >80%).19−21 After evaluation of the economic performance, the cost is not as low as expected. However, this BMED process can be labeled as 1585

dx.doi.org/10.1021/ie403847a | Ind. Eng. Chem. Res. 2014, 53, 1580−1587

Industrial & Engineering Chemistry Research

Article

Table 4. Quality Comparison between Standard Products and Experimental Products by the Integrated Production Processa volatile matter at 105 °C (%)

hydrotrope (%)

residue on sieve

iron content (%)

pH

≤1.00 ≤1.00 0.56 0.68

≤0.40 ≤0.40 0.21 0.25

≤0.10 ≤0.40 0.081 0.075

≥86.00 ≥86.00 88.14 86.95

3.5−7.0 3.5−7.0 5.8 5.6

primary standard industrial standard product I product II a

appearance yellow yellow yellow yellow

powder powder powder powder

The results are supplied by Tongling Rely Technology Co., Ltd., China.

Second, the individual BMED process was studied, and results show that when the distilled water flow rate was 0.3 L/h, operating current density was 60 mA/cm2, and modified methods were adopted, the base generated can meet the requirement of the base consumption in the air oxidation process. Third, two groups of experiments on the integrated production process were conducted, and results revealed that the integration was feasible and the products were qualified. Fourth, economic evaluation of the integrated production process was conducted; results show that the cost is slightly high, mainly because of the high cost of bipolar membranes. However, the integrated production process is feasible, effective, environmentally friendly, and “zero waste dischargeable”. If the bipolar membrane is widely commercialized, the cost of BMED will decrease, thus leading to a more economical integrated production process.

Table 5. Estimation of Process Cost in BMED integrated production process repeating units current density (mA/cm2) effective membrane area (m2) current efficiency (%) energy consumption (kWh/kg) process capacity (kg/year) electricity change ($/kg) energy cost for NaOH ($/kg) energy cost for the peripheral equipment ($/kg) total energy cost ($/kg) membrane life and amortization of the peripheral equipment (year) anion exchange membrane price ($/m2) cation exchange membrane price ($/m2) bipolar membrane price ($/m2) membrane cost ($) stack cost ($)

remarks

8 60 0.004 41.71 12.5 87.03 0.09 1.12 0.06 1.18 5

annual operation days = 300

■

204

613 31.54 47.31

peripheral equipment cost ($)

70.96

total investment cost ($) amortization ($/year) interest ($/year) maintenance ($/year)

118.27 23.65 9.46 11.83

total fixed cost ($/year) total fixed cost ($/kg) total process cost ($/kg)

44.94 0.52 1.70

ASSOCIATED CONTENT

* Supporting Information

169

S

The heating curve of the automatic programming temperature controller (Figure S1). The change in trend of the (a) aeration rate, (b) temperature, (c) pH, and (d) FeSO 4·7H 2O concentration over time during the integrated production process (Figure S2). This material is available free of charge via the Internet at http://pubs.acs.org.

1.5 times membrane cost 1.5 times stack cost

■

interest rate, 8% 10% the investment cost

AUTHOR INFORMATION

Corresponding Author

*Tel: +86 551 63601587. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This research is supported in part by the National Natural Science Foundation of China (nos. 21025626, 21206154), National High Technology Research and Development Program 863 (no. 2012AA03A608), and the Programs of Anhui Province for Science and Technology (no.11010202157). The authors are profoundly grateful to Mr. Yu Qian and Yang Cao from Tongling Rely Technology Co., Ltd., China, for providing the seed crystals and techniques for producing the yellow iron oxide pigments.

“zero waste discharge”, because during the integrated production process, (i) the produced inorganic base can be directly used in the air oxidation process, (ii) the byproducts (acid solutions) can be reused in pickling industries, and (iii) the final waste liquor was disposed and reused efficiently, and there was almost no waste liquor discharged. Modern chemical production is in pursuit of process intensification, so we cannot use the parameters of one operating unit to evaluate its feasibility. If “zero waste discharge” is taken into consideration, this process has great potential to reform the existing production technology through recycling of resources and protecting the environment.

■

REFERENCES

(1) Nobuoka, S.; Asai, T.; Ado, K. Yellow iron oxide pigment and method for manufacture thereof. U.S. Patent 4459276A, 1982. (2) Zhang, J. The preparartion and advances of ferric oxide yellow pigment (in Chinese). Liaoning Chem. Ind. 1999, 28, 28. (3) Krockert, B.; Printzen, H.; Ganter, K. Buxbaum G. Process for the production of iron oxide yellow pigment. Canadian Patent 2018462, 1989. (4) Meisen, U. Process for producing yellow iron oxide pigments. U.S. Patent 2002088374A1, 2002.

4. CONCLUSIONS An experimental study was carried out on the integration of the air oxidation process with BMED to produce yellow iron oxide pigments. First, the individual air oxidation process was investigated, and when the operational conditions were up to the standard, all the experimental products were qualified. 1586

dx.doi.org/10.1021/ie403847a | Ind. Eng. Chem. Res. 2014, 53, 1580−1587

Industrial & Engineering Chemistry Research

Article

(5) Gavogiannis, P. The production of a yellow iron oxide pigment. EP Patent 0030790, 1984. (6) Zheng, M.; Yang, W. Study on producing yellow ferric oxide with by-product copperas of titanium white and waste acid. China Resour. Compr. Utilization 2011, 29, 22. (7) Ye, G.; Ouyang, H.; Li, R. The process of preparing yellow iron oxide pigments by using steel pickling. Chinese Patent 88107682.1, 1988. (8) Zhang, X.; Li, C.; Wang, Y.; Luo, J.; Xu, T. Recovery of acetic acid from simulated acetaldehyde wastewaters: Bipolar membrane electrodialysis processes and membrane selection. J. Membr. Sci. 2011, 379, 184. (9) Wang, X.; Wang, Y.; Zhang, X.; Xu, T. In situ combination of fermentation and electrodialysis with bipolar membranes for the production of lactic acid: Operational compatibility and uniformity. Bioresour. Technol. 2012, 125, 165. (10) Huang, C.; Xu, T.; Yang, X. Regenerating fuel-gas desulfurizing agents by using bipolar membrane electrodialysis (BMED): Effect of molecular structure of alkanolamines on the regeneration performance. Environ. Sci. Technol. 2007, 41, 984. (11) Bailly, M. Production of organic acids by bipolar electrodialysis: Realizations and perspectives. Desalination 2002, 144, 157. (12) Xu, T. Electrodialysis processes with bipolar membranes (EDBM) in environmental protection-a review. Resour., Conserv. Recycl. 2002, 37, 1. (13) Xu, T.; Yang, W. Effect of cell configurations on the performance of citric acid production by a bipolar membrane electrodialysis. J. Membr. Sci. 2002, 203, 145. (14) Vera, E.; Ruales, J.; Dornier, M.; Sandeaux, J.; Sandeaux, R.; Pourcelly, G. Deacidification of clarified passion fruit juice using different configurations of electrodialysis. J. Chem. Technol. Biotechnol. 2003, 78, 918. (15) Onishi, N.; Osaki, T.; Minagawa, M.; Tanioka, A. Alcohol splitting in a bipolar membrane and analysis of the product. J. Electroanal. Chem. 2001, 506, 34. (16) Strathmann, H.; Koops, G. Process economics of electrodialytic water dissociation for the production of acid and base. In Handbook on Bipolar Membrane Technology; Kemperman, A. J. B., Ed.; Twente University Press: Enschede, 2000; p 29. (17) Wang, Y.; Zhang, X.; Xu, T. Integration of conventional electrodialysis and electrodialysis with bipolar membranes for production of organic acids. J. Membr. Sci. 2010, 365, 294. (18) Wang, Y.; Wang, A.; Zhang, X.; Xu, T. Simulation of electrodialysis with bipolar membranes: Estimation of process performance and energy consumption. Ind. Eng. Chem. Res. 2011, 50, 13911. (19) Shen, J.; Huang, J.; Liu, L.; Ye, W.; Lin, J.; Bruggen, B. The use of BMED for glyphosate recovery from glyphosate neutralization liquor in view of zero discharge. J. Hazard. Mater. 2013, 260, 660. (20) Alvarez, F.; Alvarez, R.; Coca, J.; Sandeaux, J.; Sandeaux, R.; Gavach, C. Salicylic acid production by electrodialysis with bipolar membranes. J. Membr. Sci. 1997, 123, 61. (21) Huang, C.; Xu, T.; Jacobs, M. Regenerating flue-gas desulfurizing agents by bipolar membrane electrodialysis. AIChE J. 2006, 52, 393.

1587

dx.doi.org/10.1021/ie403847a | Ind. Eng. Chem. Res. 2014, 53, 1580−1587