Chemical Engineering Journal 314 (2017) 223–231 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Sorption performance and mechanisms of arsenic(V) removal by magnetic gelatin-modified biochar ⇑ ⇑ Zan Zhou a,b, Yun-guo Liu a,b, , Shao-bo Liu c, , Hong-yu Liu a,b,d, Guang-ming Zeng a,b, Xiao-fei Tan a,b, Chun-ping Yang a,b, Yang Ding a,b, Zhi-li Yan a,b, Xiao-xi Cai a,b,d a College of Environmental Science and Engineering, Hunan University, Changsha 410082, PR China b Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, PR China c School of Metallurgy and Environment, Central South University, Changsha 410083, PR China d College of Art and Design, Hunan First Normal University, Changsha 410205, PR China highlights graphical abstract A novel of magnetic gelatin-modified biochar was sythesized. The maximum adsorption capacity of As(V) on MG-CSB is 45.8 mg gÀ1 at 298 K pH 4.0. The adsorption was an endothermic process and could be described by Langmuir. As–O interactions and electrostatic interactions was the main adsorption mechanism. article info abstract Article history: A new environmentally friendly and low-cost adsorbent to remove As(V) from industry waste water was Received 20 November 2016 synthesized by the mixture of 723 K pyrolyzed chestnut shell and magnetic gelatin. The resultant biochar Received in revised form 23 December 2016 was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Accepted 25 December 2016 Fourier transform infrared spectrometer (FT-IR) and vibrating sample magnetometer (VSM). Magnetic Available online 27 December 2016 gelatin microsphere enlarged the specific surface area of pristine biochar so the modified biochar had more adsorption sites for arsenic(V) removal. Also, it had strong magnetic property so it could be easily Keywords: separated from aqueous solution. Batch sorption experiment results showed that the maximum adsorp- Arsenic(V) tion capacity was 45.8 mg gÀ1, which was higher than that of the unmodified (17.5 mg gÀ1) and some Biochar Magnetic gelatin other biochar. All findings illustrated that this new material could be used to deal with arsenic(V)- Adsorption containing waste water effectively. Ó 2016 Elsevier B.V. All rights reserved. 1. Introduction tions with the development of industry. It has been demonstrated that arsenic does great harm to human health and has already been Arsenic is one of the most common and harmful pollutants in taken as group one carcinogens by the International Agency for environment throughout the world, especially in aqueous solu- Research on Cancer (IARC) [1]. The World Health Organization (WHO) has professed that the maximum concentration of arsenic l À1 ⇑ Corresponding authors at: College of Environmental Science and Engineering, in drinking water is 10 gL [2]. Thus, developing effective and Hunan University, Changsha 410082, PR China (Y.-g. Liu). potent wastewater treatment technology for As(V) removal has E-mail addresses: [email protected] (Y.-g. Liu), [email protected] motivated extensive research. (S.-b. Liu). http://dx.doi.org/10.1016/j.cej.2016.12.113 1385-8947/Ó 2016 Elsevier B.V. All rights reserved. 224 Z. Zhou et al. / Chemical Engineering Journal 314 (2017) 223–231 At present, kinds of methods including precipitation [3], lime of this study was to research a new cost-effective material to softening [4], adsorption [2], membrane separation [5], ion remove the As(V) from aqueous solution. exchange [6] have being tested by many researchers, which demonstrated that these processes all have effects in arsenic 2. Materials and methods uptake at different levels. Sorption is one of the most commonly and effectively used methods due to its ease of operation, relatively 2.1. Chemical reagents low cost, and no sludge disposal [7]. Various types of sorbents have been developed and applied for water treatment during the past All the chemical reagents used were of chemical grade and solu- few decades. Among them, iron oxy-hydroxide powders were con- À tions were prepared using high purity water (18.25 MX cm 1) sidered to be one of the most efficient sorbents for arsenic in aque- from a Millipore Milli-Q water purification system. Ferric chloride ous solution. However, separation of spent iron-oxy hydroxides (FeCl ), ferrous chloride (FeCl ), disodium hydrogen arsenate (Na - particles requires sedimentation or filtration, which results in 3 2 2 HAsO Á7H O) were purchased from Fisher Scientific. Chestnut additional cost and mechanical resistance [8]. Activated carbon 4 2 shells were collected from local farm in Changsha, China. (AC) is another sorbent that has been widely used to remove water pollutants because of its high specific surface area, abundant sur- face functional groups, and well-developed pore structures. How- 2.2. Synthesis of materials ever, AC is not suitable for removing some anionic contaminants such as arsenic most likely because of its negative charged surface Chestnut shell was natural withering for 3 days and then was [9]. Alternative and low-cost sorbents thus are still needed for the sifted out by 0.2 mm sieve. The feedstock was placed in ceramic removal of arsenic from aqueous solutions. crucible with a lid. Biochar was prepared by pyrolyzing the bio- Recently, there are many researches of producing and optimiz- mass in a lab-scale tubular reactor (SK-G08123 K, China) under ing adsorbent materials with similar characteristics to activated N2 at a peak temperature of 723 K for 2 h. The biochar produced carbon materials but less costly and more environmental friendly. were sieved to obtain particles between 0.07 mm and 0.2 mm Of which, biochar is a suitable one [10]. Biochar is a solid carbon- and then saved in a sealed container for later use. Modified biochar rich residue produced by thermal decomposition of plant-derived was made by the following steps: First, put 0.2 g gelatin in 500-mL biomass (oxygen-limited pyrolysis) in the partial or total absence beaker containing 200 mL deionized water, then put the beaker at of oxygen [11]. There are abundant oxygen-containing functional 358 K water bath for about half an hour. Then 0.02 M FeCl3 and groups on biochar, e.g. carboxylate (ACOOH), carbonyl (ACOH) 0.01 M FeCl2 was dissolved in 200 mL high purified water, respec- 2+ and hydroxyl (AOH) [12]. Biochar normally carry a net negative tively. When the gelatin was completely dissolved, the Fe and 3+ charge on their surfaces due to the dissociation of oxygen- Fe solution were added into the beaker at the same time proba- containing functional groups [13], and therefore can be used as bly, biochar was added into it at last (gelatin: biochar = 1:1). Tem- low-cost adsorbents to remove organic pollutants and heavy metal perature was then turned down to 328 K and the mix was shook at cations from water [14]. There are many types of biochar from dif- 275 rpm for 2 h. The produced biochar was separated from the liq- ferent biomass, such as municipal sludgy, poultry litter, dairy man- uid after the reaction and further washed with deionized water to ure, paper sludge [15–17]. However, these biochar materials were neutral. After these, the resultant biochar should be filtered, dried hard to selectively adsorb pollutants. To enhance their capacity and placed under a limited oxygen condition. The biochar with and and selectivity for pollutant removal, modification of carbon mate- without magnetic gelatin modification were denoted as MG-CSB rials has attracted many attentions in recent years [18]. Several and CSB, respectively. methods (acid and alkali modification, oxidation, and chemical graft) have been used to modify biochar and improve its adsorption 2.3. Batch aqueous As(V) adsorption performance of pollutants [19]. In general, these techniques can both modify the physical properties and chemical reactivity of bio- Batch sorption experiments were carried out at room tempera- char by increasing the specific surface area and forming surface ture (298 ± 2 K) by adding 20 mg sorbent to 200-mL glass conical functional groups that can be chemically bonding with the pollu- flask containing 50 mL As(V) solution. The pH of solution was in tants [20]. the range of 2–11 and it was adjusted for each experiment using Gelatin is an important naturally high polymer material. It is 0.01 M NaOH and 0.01 M HCl. After shaking 24 h in a rotary shaker made by animal’s bone or meat which is rich in amino acid. It (SHY-2A, China) for equilibration sorption, the mixture was filter- has been widely used in some fields such as medicine, foods, indus- ing by Chemical analytical filter paper. Concentrations of As(V) in try because of its biodegradability and biocompatibility in physio- the supernatants were determined using atomic fluorescence spec- logical environments [21]. There are lots of oxygen-containing trometer (AFS-9700, China). The amounts of adsorbed As (Qt) per functional groups in gelatin, which could be loaded onto biochar unit sorbent mass were calculated based as the differences to enhance biochar’s adsorption capacity. Iron ion addition is a between initial and final aqueous solution concentrations. The good solution to overcome the difficulty of adsorbents separation residual solids were washed with deionized water and then oven in aqueous solution [22,23]. To our best knowledge, research on dried (353 K) and stored for analysis using SEM, FT-IR and XPS. 2À 2À À + + + the modification of biochar with magnetic gelatin has not been Influence of co-existing anions (SO4 ,PO4 ,NO3 ,Na,K,Ca, reported. Mg2+,Ca2+ and Mn2+ of 0.01, 0.1 and 1 mol LÀ1, respectively) on In this study, biochar was modified by magnetic gelatin and it As(V) (20 mg LÀ1) sorption onto MG-CSB was carried out using showed efficient adsorption capacity to As(V).