Wu Coconutcharcoal Environ Sci Pollut Res 2013

RESEARCH ARTICLE Comparative and competitive adsorption of Cr(VI), As(III), and Ni(II) onto coconut charcoal Yunhai Wu & Yajun Wen & Jianxin Zhou & Julin Cao & Yanping Jin & Yunying Wu Received: 30 May 2012 /Accepted: 2 July 2012 /Published online: 13 July 2012 # Springer-V erlag 2012 Abstract This study evaluates the behavior of coconut charcoal (AC) to adsorb Cr(VI), As(III), and Ni(II) in mono- and multicomponent (binary and ternary) systems. Batch experiments were carried out for mono- and multicomponent systems with varying metal ion concentrations to investigate the competitive adsorption characteristics. The adsorption kinetics followed the mechanism of the pseudo- second-order equation in both single and binary systems, indicating chemical sorption as the rate-limiting step of adsorption mechanism. Equilibrium studies showed that the adsorption of Cr(VI), As(III), and Ni(II) followed the Langmuir model and maximum adsorption capacities were found to be 5.257, 0.042, and 1.748 mg/g, respectively. In multicomponent system, As(III) and Ni(II) adsorption com- peted intensely, while Cr(VI) adsorption was much less affected by competition than As(III) and Ni(II). With the presence of Cr(VI), the adsorption capacities of As(III) and Ni(II) on AC were higher than those in single system and the metal sorptio n followed the order of Ni(II)>As(III)>Cr (VI). The results from the sequential adsorption – desorption cycles showed that AC adsorbent held good desorption and reusability. Keywords Adsorption . Cocon ut charcoal . Equilibrium . Kinetics . Metal . Multicomponent . Sing le system Nomenclature b Langmuir adsorption constant (liters per milligram) C 0 Initial con centration of solute in solution (m illigrams per liter) C e Equilibrium concentration of solute in bulk solut ion (milligrams per liter) E Mean fr ee energy of adso rption (kilojoules per m ole) k 1 Equilibrium rate constant of pseudo-first-order sorption (per minute) k 2 Equilibrium rate constant of pseudo-second-order sorption (grams per(milligrams per minute)) K Constant related to f ree ener gy (i n squar e moles per square kilojoules) K f Freundlich constant indicative of the relative sor ption capacity of the sorbent (milligrams per gram) n Freu ndli ch const ant indi cati ve of the inte nsit y of sorption q e Amo unt of solu te adso rbed per unit weig ht of adso rben t at equilibrium (milligrams per gram) q t Amo unt of solu te adso rbed per unit weig ht of adso rben t at any time (milligrams per gram) Q m Mon ola yer maxi mum adsorpt ion capa cit y of the sor ben t (milligrams per gram) r 2 Correlation coefficient R Gas constant (8.314 J/(moles per Kelvin)) R L Langmuir separation factor t Time (minute) T Absolute temperature (Kelvin) Greek letters α Elovich constant indicative of the initial sorption rate (milligrams per (grams per minute)) β Desorption con stant of Elovich (gr ams per m illigram) ε Polanyi potential Responsible editor: Vinod Kumar Gupta Y. Wu Key Laboratory of Integrated Regulation and Resources Development of Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, Chin a Y. Wen : J. Zhou : J. Cao : Y. Jin College of Environment, Hohai University, Nanjing 210098, Chin a Y. Wu (*) Department of Chemistry, Hanshan Normal University, Chaozhou, China e-mail: [email protected] Environ Sci Pollut Res (2013) 20:2210 – 2219 DOI 10.1007/s11356-012-1066-y

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Wu Coconutcharcoal Environ Sci Pollut Res 2013