Effect of acid and hydrothermal treatments on the multilayer adsorption of Cr(VI) and dyes on biomass-derived nano/mesop
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Effect of acid and hydrothermal treatments on the multilayer adsorption of Cr(VI) and dyes on biomassderived nano/mesoporous carbon Xianwen Zhang1, Yingzi Ge1, Guoting Zhu2, Jingchun Tang1, Xianjun Xing3,a), Na Li4,b) 1
School of Automobile and Transportation Engineering, Hefei University of Technology, Hefei, Anhui 230009, China Anhui Resource Saving & Environmental Technology Co., Ltd., Hefei, Anhui 230088, China 3 Institute of Advanced Energy Technology & Equipment, Hefei University of Technology, Hefei, Anhui 230009, China 4 Department of Chemistry and Chemical Engineering, Hefei Normal University, Hefei, Anhui 230601, China a) Address all correspondence to these authors. e-mail: [email protected] b) e-mail: [email protected] 2
Received: 24 February 2019; accepted: 9 April 2019
Nano/mesoporous carbon was prepared from pine wood sawdust via the pretreatment of acid and hydrothermal process, followed by potassium hydroxide (KOH) activation. This study proposed the enhancement of activated carbon (AC) adsorption capacity by utilizing the vacant sites and phenomena of opposite charge attraction via multilayer adsorption of Cr(VI) ions and dyes with positive and negative charges. On the first layer, the maximum adsorption capacities for Cr(VI) ions, methylene blue (MB) molecules, and acid red 18 (AR18) molecules onto AC were found to be 7.91 mg/g, 476.19 mg/g, and 434.78 mg/g, respectively. For multiple adsorption, after Cr(VI) ions uptake saturation, the sequential adsorption of MB and AR18 on the second layer, the maximum adsorption capacity, reached 322.58 mg/g and 333.33 mg/g. After MB and AR18 uptake saturation, the maximum Cr(VI) adsorption capacity reached 2.92 mg/g and 4.39 mg/g.
Introduction Heavy metals and dyes in wastewater are the dangerous pollutants, originating in large quantities from metal plating facilities, paints and pigments manufacturing, textile as well as pulp and paper industries [1, 2]. According to the list of priority pollutants of the US Environmental Protection Agency (EPA), chromium ions represent a serious problem for the human health because they are not biodegradable and tend to accumulate in living organisms causing several diseases that affect the kidney, nervous, hematopoietic, and gastrointestinal systems of humans [3, 4]. Additionally, some dyes discharged from the textile, printing, and tanning industries commonly are toxic, no degradable, stable, and even carcinogenic, causing deterioration in water quality, influencing the photosynthetic activity of aquatic organism [5]. Therefore, it is urgent to find an efficient and cost-effective method to remove these pollutants [6]. Nowadays, some treatment processes are used for the removal of heavy metals and dyes from wastewater, including
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ion-exchange, adsorption, membrane filtration, coagulation, and flocculation [7, 8]. However, ion-exchange is expensive and accumulation of concentrated sludge caused by ionexchange creates
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