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Sorption of Methylene Blue and Congo Red on Biochars Derived from Hickories, Mosses and Pine Needles
Received:March 13, 2015  
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KeyWord:biochar;dye;adsorption isotherm;adsorption kinetics
Author NameAffiliationE-mail
WU Hai-lu School of Environment, Nanjing University of Technology, Nanjing 211816, China  
CHE Xiao-dong School of Environment, Nanjing University of Technology, Nanjing 211816, China  
DING Zhu-hong School of Environment, Nanjing University of Technology, Nanjing 211816, China dzhuhong@njtech.edu.cn 
HU Xin Center of Material Analysis, Nanjing University, Nanjing 210093, China  
CHEN Yi-jun Center of Material Analysis, Nanjing University, Nanjing 210093, China  
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Abstract:
      Re-utilization of agricultural wastes not only reduces environmental pollution but also alleviates resources shortages, thus promoting the sustainable development of agriculture. Among waste-utilizing technologies, biomass pyrolysis to produce biochar at limited oxygen conditions is receiving increasing attentions. Biochar can reduce carbon emissions and is often used as adsorbents in wastewater treatments and soil remediation. In the present study, biochars produced from hickories, mosses and pine needles were used to examine the effects of solution pH, contacting time and initial concentrations of adsorbates on the sorption of congo red (CR) and methylene blue (MB) on three biochars. Strong alkaline medium was beneficial to the sorption of methylene blue, while acidic conditions favored the adsorption of congo red. The adsorption isotherms of methylene blue and congo red followed the Freundlich equation. The adsorption of both MB and CR increased with the initial concentrations of the dyes, and occurred mainly within 1 h. The dynamic adsorption process of the dyes fitted the pseudo second-order kinetic model and the intra-particle diffusion was the rate-controlling stage. These three biochars showed no significant difference in adsorption capacities for the dyes.