Novel lignocellulosic wastes for comparative adsorption of Cr(VI): equilibrium kinetics and thermodynamic studies

Polish Journal of Chemical Technology

Haroon Hajira¹  Pervez Arshid¹  Mahmood Qaisar¹  Bilal Muhammad¹  Gardazi Syed Mubashar Hussain¹  Butt Tayyab Ashfaq² 

[1] COMSATS Institute of Information Technology, Department of Environmental Science, Abbottabad, 22060, KPK, Pakistan;University of Hail, Department of Civil Engineering, Hail Province, Saudi Arabia;

关键词: chromium vi;    equilibrium kinetics;    lignocellulosic waste adsorbents;    thermodynamics;   

DOI  :  10.1515/pjct-2017-0021

来源: DOAJ

【 摘 要 】

Cr(VI) adsorption was studied for abundantly available low-cost lignocellulosic adsorbents in Pakistan namely, tobacco stalks (TS), white cedar stem (WCS) and eucalyptus bark (EB). Several process variables like contact time, adsorbent dose, pH, metal concentration, particle size and temperature were optimized in batch mode. EB showed high Cr(VI) adsorption of 63.66% followed by WCS 62% and TS 57% at pH 2, which is higher than most of the reported literature. Langmuir isotherm (R2 = 0.999) was well fitted into the equilibrium Cr(VI) data of EB, suggesting homogeneous active sites and monolayer coverage of Cr(VI) onto the EB surface. Freundlich (R2 = 0.9982) isotherm was better fitted to the equilibrium data of TS and WCS, revealing the adsorption sites with heterogeneous energy distribution and multilayer Cr(VI) adsorption. Moreover, the Cr(VI) adsorption of studied adsorbents followed the pseudo-second order kinetic model. Thermodynamic properties were investigated in two temperature ranges, i.e., T1 (303–313 K) and T2 (313–323 K). TS and EB showed the exothermic at T1 and endothermic reactions at T2 with entropy controlled adsorption at the solid-liquid interface, and WCS exhibited an opposite thermal trend with decreasing disorderness at solid-liquid interface as temperature rises. Gibbs free energy (ΔG>0) confirmed the non-spontaneous adsorption process for all studied adsorbents.

【 授权许可】

Unknown