Highly Efficient and Rapid Lead(II) Scavenging by the Natural Artemia

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Highly Efficient and Rapid Lead (II) Scavenger by Natural Artemia Cyst-shell with Unique Three-Dimension Porous Structure and Strong Sorption Affinity Bo Wang, Junling Xia, Liyong Mei, Lei Wang, and Qingrui Zhang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b03667 • Publication Date (Web): 20 Nov 2017 Downloaded from http://pubs.acs.org on November 26, 2017

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ACS Sustainable Chemistry & Engineering

Highly Efficient and Rapid Lead (II) Scavenger by Natural Artemia Cyst-shell with Unique Three-Dimension Porous Structure and Strong Sorption Affinity Bo Wangǁ§, Junling Xia†‡, Liyong Mei§, Lei Wang§, and Qingrui Zhang†‡*

†

State Key Laboratory of Metastable Materials Science and Technology, Yanshan University,

Qinhuangdao 066004, P. R. China ‡

Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering,

Yanshan University, Qinhuangdao 066004, China §

Shenzhen-HongKong Institution of Industry, Education Research Environmental Engineering

Technique Co., LTD, 518071, Shenzhen, China ǁ

Peking University Shenzhen Graduate School, 518055, Shenzhen, China.

*To whom correspondence should be addressed (Qingrui Zhang ) E-mail: [email protected]/ Tel.: +86-335-8387-741 Fax: +86-335-8061-549

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ACS Paragon Plus Environment


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Abstract Heavy metal purification of water is a world-wide issue. In this work, we first find that the discarded Artemia cyst-shell exhibits a unique three-dimension porous structure, which can be recycled for efficient toxic Pb(II) removal. The hierarchical skeleton comprised of the macro-meso-micropore confirmation and as well as 17 types of amino acid species provides fast ion-accessibility and a strong sorption affinity. The results prove that an extremely rapid Pb capture is obtained in less than 2 min, and strong adsorption occurs in the presence of high concentration of Ca/Mg/Na ions, and selectivity is far beyond that of the commercial 001x7 (greater than 50 times). More importantly, an efficient application is achieved with a treatment capacity of 9100 kg wastewater/ kg sorbent, which is 45 times greater than the performance of commercially-activated carbon and ion exchange resin. The effluent can be dramatically reduced to below 10 µg/L level (WHO). In addition, we can also regenerate the exhausted biomaterial Artemia shell for several cycles. All the results demonstrate that the unique structure and amino acid skeletons make discarded Artemia shells new application for trace lead removal at low-cost.

Keywords: Heavy metal; Artemia; lead (II); purification;

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Introduction Water pollution by heavy metals remains a serious environmental and public health threat, even in trace amounts1. For instance, trace levels of cadmium can significantly magnify the cancer-causing potential by inhibiting the ability to repair DNA 2. To date, various methods, including chemical precipitation, adsorption, ion-exchange and membrane, have been proposed to conquer the problems, and adsorption technology appears to be an efficient approach3，due to its simplicity and effectiveness. Developing effective materials, thus, is an important route to sequestering trace metals. The ability to easily apply the adsorbent and the rapid decrease of trace pollutants to safe levels are important criteria. Recently, Zare and his coworkers4 in Stanford University discovered the protein-induced hybrid nanoflowers. The unique 3D molecular structure of various proteins/ enzymes (BSA, beta-lactalbumin) and strong amide groups will readily form a powerful Cu-complex and then bloom into the flower-shaped hybrid nanostructures. More importantly, the prepared protein-bearing nanomaterials can achieve superior heavy metal sequestration through the preferential reaction of amide or carboxyl groups within the protein matrix5, 6. Bolisetty et al.7 first prepared the protein fibrils membrane, which demonstrates an exceedingly large sorption capacity and rapid purification for various toxic metals. In addition, Polydopamine, inspired from the mussel-protein are also proved to be an effective adsorbent and coating substrate for trace heavy metal retention and various applications8-12. Therefore, protein based materials and their derivatives are potential new reforms for efficient metal-adsorbent exploration in water purification. Similar to the protein-bearing materials, Chitosan and its derivatives have been emerging as efficient metal scavengers due to their abundance of aminated terminates and environmental benign property13, 14. In addition the chitosan catalog material can readily attach by morphology or shapes 3



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confirmation through a cross-linking reaction, which is convenient for sequestering various metals 15, 16

. However, the obtained biomaterials are always sensitive to some water constituents;

particularly, the coexistence of high salts content and organic components are a serious threat to its chemical stability in wastewater treatment. Brine shrimp Artemia is important bait and food sources in fish cultivation, e.g., P. monodon, Eriocheir

Sinensis, prawn etc., which is a representative specie, that lives in most high salt

regions, (e.g., salts lakes/fields and oceans), such as the famous Great Salt Lake of The USA17. According to available statistics, worldwide approximately 18000 tons of Artemia were consumed for various shrimp or fish feedings in one year18 and several international enterprises (e.g., NUTRI-AD International) have engaged in the Artemia cultivation and marketing. Unfortunately, the discarded cyst-shells are always disposed as wastes after nauplii collection. Thus, the application of the discarded cyst-shells is an important research issue. Additionally，it is also an ideal support for self-assembled nanomaterials design19-24. Considering the hypersaline living environment of Artemia nauplii, the discarded Artemia cyst-shells exhibit biocompatibility, environmental friendly and have a remarkable tolerance to extremely harsh conditions. For instance, Artemia eggs can remain stable at extreme temperatures from −271 °C to 110 °C, under Χ-ray radiation, in high salt, oxygen-deficient environments and are resistant to oxidative damages while shielding the encysted embryos25-27. Such excellent properties, far beyond those of other common protein biomaterials, make cyst shells potentially exceptional material in the environmental remediation realm. Interestingly, Artemia cyst shells also display a unique hierarchically structured skeleton; the shell of Artemia cysts is composed of an outer surface lamella and three-dimensional interior pore regions (Figure 1c). The outer region is particularly rich in Ca(II), P species, which protects the 4


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embryos from severe external environments, while the interior 3D hierarchical structures can be divided into the transitive deep mesoporous/microporous section and the macroporous morphology with a size of 20 nm-1µm, which favors the rapid metal ions accessibility. More importantly, the unique skeleton with a broad honeycomb like morphology mainly consists of large amounts of chitin, and 17 kinds of natural amino acid28, 29, thus, the thriving amides and carboxyl groups can bond with the target heavy metals. In this work, we firstly gain a new insight into the discarded Artemia cyst-shell wastes for use in heavy metal sequestration. Different from the conventional efficient biomaterials, Artemia Cyst-shells have excellent chemical stability against various severe environments30. The amides and carboxyl components of the matrix can provide a strong affinity to target toxic metals, while the unique 3D transitive pore morphology will further enhance ion accessibility and the utilization of active sites. Therefore, rapid and efficient application performance for heavy metal removal can be assumed. Pb(II), listed in the priority pollutants, is selected as model heavy metal for evaluation and XPS investigation is also employed to elucidate the possible sorption mechanism.

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Materials and method Materials All the chemical reagents used in this work are of analytical grade without further purification, and were purchased from Tianjin Chemical Reagent Station, China. The Artemia cyst-shells were kindly provided by Shenzhen-HongKong Institution of Industry. The referred materials of commercial cationic exchange resin 001x7 was obtained from Nanjing Resin Co. with the particle size of 0.6-0.8 mm, and the polystyrene skeleton was modified with SO3-H groups of 3.9 meq/g capacity，prior to use，the completely washing is necessary to remove the possible residues. Treatment of the Artemia cyst-shells The Artemia cyst-shells is treated with the following procedures. A total of 5 g of raw Artemia cyst-shells were added into a 300 mL water- ethanol mixture (50% wt) and were stirred for 5 hours to wash the raw cyst shells to remove the salt and possible residues. The above procedures were repeated for 3-4 cycles. Afterward, the Artemia cyst-shells were subjected to ultrasonic processing for 30 mins to achieve pore perforation and water infiltration. The resultant materials gradually gravitate towards the water bottom, suggesting complete water saturation. Finally, the Artemia cyst-shells were filtrated and then heat treated at 60oC for 8 hours. Batch sorption runs A series of batch sorption experiments were performed through the conventional bottle-point method and the detailed procedures are listed as follows： Solution pH effect on Lead(II) removal：25.0 mg of Artemia cyst-shells were introduced into a plastic bottle containing a 50 mL solution with 0.25 mM lead(II) ions, and 1% HCl or NaOH was addd to adjust the solution to desired pH. Afterward, the above bottles were transferred to an incubator shaker (SH85, Huxi China) under a constant shaking speed of 200 rpm for 2 h at the desired temperatures. An approximately 2 h reaction is enough to reach the final sorption 6


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equilibrium, and then the sorbent was filtrated from the remaining solution concentration and the corresponding pH was determined. In addition This Pb species distribution is calculated using the software of Visual Minteq with the initial Pb concentration of approximately 0.25 mmol/L, which is equal to the Pb concentration in the section of pH effects. Zeta potential tests were carried out with the following procedure: Suspensions containing 0.25 g/L Artemia cyst-shell (ground into powders) were well stirred at room temperature for 10 h, afterward, it was subjected to performing a ultrasonic bath for 20 min for ensure well dispersion. The solution pH of the suspension was adjusted to 1.0-7.0 using 0.10 M HCl or NaOH, next the above suspension was further stabilized for 6 h to attach the charge equilibrium. The solution pH at equilibrium was determined and the samples were used for the measurement of zeta potentials by Zeta-plus 4 instruments (Brookhaven Instrument Co.,USA) , the values were tested for five times to ensure the reliability The competing experiments were conducted involving adding commonly present Na(I), Mg(II), and Ca(II) at different concentrations, the initial Pb concentration is around 50 mg/L at 298K, with 0.5 g/L sorbent, pH =6.2-6.8. The series bottles were transferred to an incubator shaker for 2 h shaking to approach sorption equilibrium. Finally, the lead uptakes onto sorbents are calculated by conducting a mass balance before and after the test. Kinetic tests were carried out to evaluate the sorption behaviors. Specifically, 0.5 g of Artemia cyst-shells were introduced into a 500-mL solution containing 30 mg/L of lead ions. Mechanical stirring was performed to ensure an identical reaction and complete mixing and 0.5 mL of the solution was sampled at different time intervals. The sample concentrations and sampling time were recorded for the calculation sorption capacities. 7



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Sorption isotherm tests were conducted to evaluate the maximum sorption capacity at different temperatures. To be specific, 50 mg of treated Artemia Cyst-shells were introduced into series bottles containing 50 mL solution with different concentrations of lead(II) ions, the added dose of 1 g/L. the initial different Pb concentrations of 20 mg/L, 50 mg/L, 100mg/L, 150 mg/L, 200 mg/L, 400 mg/L, 600 mg/L. the solution pH at equilibrium is around 6.2-6.6. The above bottles were transferred to an incubator shaker for 10 h shaking at desired temperatures (20oC/40oC/60oC/), afterward, the lead(II) contents in effluent were assayed and the maximum sorption capacity can be well calculated by the classic Langmuir or Freundlich models. It is noteworthy that the concentration of Pb(II) in this section is very high, which is not agree with the real wastewater, but, this work aims at reflecting the maximum sorption ability, the actual application tests were performed in the section of fixed-bed column sorption. It is noted that prior to conduct the experiment, all the treated Artemia cyst shells were well dried at 333 K in a vacuum for 24 hours to avoid the possible effects on weight, besides, the cyst shells is extremely light and one mg adsorbent contains approximately 20-25 shells. Therefore, at this condition, the dose of 0.5 g/L or 1.0 g/L is believable. Fixed-bed column sorption and regeneration Fixed bed column experiments were performed to evaluate the applicability of the given Artemia cyst shells. A total of 3 mL of sorbents were packed in a glass column (12 mm in diameter and 25cm in length), which was equipped with a water bath apparatus to maintain a constant temperature. A peristaltic pump (lange-580, China) was employed to ensure the feeding flow rates and an automatic fraction collector was used to collect the effluents at various time intervals. In addition, the exhausted materials can be readily regenerated using 1% HCl solution to strip the adsorbed Pb(II). Prior to the next adsorption cycles, complete washing of the Artemia cyst-shells is 8


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necessary until neutral pH conditions are obtained. The fixed-bed adsorption was performed with the following sorption hydrodynamic conditions: the superficial liquid velocity (SLV), 0.50 m/h; the empty bed contact time (EBCT), 6 min, and those for regeneration were: SLV, 0.15 m/h and EBCT 24 min. Analysis and characterization The lead (II) ions concentration in the solution was determined using an atomic absorption spectroscope (AAS06800, Shimazu), while the trace level (>Ca (II). Next the detailed sorption behaviors and mechanism were further elucidated. Solution pH effects on Pb removal Solution pH effects on Pb sequestration were also conductive to determine the sorption process 11



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(Figure 3a). It can be observed that the lead (II) adsorption onto Artemia CS is a solution pH-dependent process and three sorption stages are observed. Specifically, the zero-adsorption region (pH 5.5). The interesting behaviors might be partially ascribed to the surface charges of Artemia CS and different Pb species. The zero potential charges of Artemia CS are obtained at pHzpc =2.53(Figure 3b), and a positive charge onto the surface of Artemia CS can be approached at pH 2.5 can be associated with the negative surface adsorption. In addition, the strong complexation between the amides / carboxyl component of matrix and target Pb will further promote the powerful sequestration. It is also observed that a monovalent Pb(OH)+ exhibits a gradual increase distribution at pH>5.0 (Figure 3c) , thus, more Pb species can be adsorbed by comparing bivalent Pb2+ ions. It is noteworthy that there is no precipitation occurrence at this pH stage. More importantly, the negligible adsorption at acidic surroundings (pH

Highly Efficient and Rapid Lead(II) Scavenging by the Natural Artemia

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