Coconut coir as biosorbent for Cr(VI) removal from laboratory wastewater

Published Date
30 November 2008, Vol.159(2):252–256, doi:10.1016/j.jhazmat.2008.02.014

Author 

Mário H. Gonzalez ^a,c

Geórgia C.L. Araújo ^b

Claudia B. Pelizaro ^a,c

Eveline A. Menezes ^a,c

Sherlan G. Lemos ^c

Gilberto Batista de Sousa ^a

Ana Rita A. Nogueira ^a,,,

• aGrupo de Análise Instrumental Aplicada, Embrapa Pecuária Sudeste, P.O. Box 339, 13560-970 São Carlos, SP, Brazil
• bEscola de Artes, Ciências e Humanidades da Universidade de São Paulo, Av. Arlindo Bettio, 1000, Ermelino Matarazzo, 03828-000 São Paulo, SP, Brazil
• cDepartamento de Química, Universidade Federal de São Carlos, Rodovia Washington Luis, P.O. Box 245, 13565-905 São Carlos, SP, Brazil

Received 21 December 2006. Revised 8 February 2008. Accepted 11 February 2008. Available online 15 February 2008.

Abstract

A high cost-effective treatment of sulphochromic waste is proposed employing a raw coconut coir as biosorbent for Cr(VI) removal. The ideal pH and sorption kinetic, sorption capacities, and sorption sites were the studied biosorbent parameters. After testing five different isotherm models with standard solutions, Redlich–Peterson and Toth best fitted the experimental data, obtaining a theoretical Cr(VI) sorption capacity (SC) of 6.3 mg g⁻¹. Acid–base potentiometric titration indicated around of 73% of sorption sites were from phenolic compounds, probably lignin. Differences between sorption sites in the coconut coir before and after Cr adsorption identified from Fourier transform infrared spectra suggested a modification of sorption sites after sulphochromic waste treatment, indicating that the sorption mechanism involves organic matter oxidation and chromium uptake. For sulphocromic waste treatment, the SC was improved to 26.8 ± 0.2 mg g⁻¹, and no adsorbed Cr(VI) was reduced, remaining only Cr(III) in the final solution. The adsorbed material was calcinated to obtain Cr₂O_3, with a reduction of more than 60% of the original mass.

Keywords

Cr(VI)

Biosorption

Coconut coir

Sulphochromic wastewater treatment

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