Studies on chromium(III) removal from aqueous solutions by sorption on Sphagnum moss peat

• Published in: Journal of the Serbian Chemical Society 2009, Vol.74 (8-9), p.953-964
• Main Authors: Balan, Catalin, Bilba, Doina, Macoveanu, Matei
• Format: Article
• Language: English
• Subjects: cr(iii),sorption; equilibrium studies; kinetics; sphagnum moss peat
• ISSN: 0352-5139; 1820-7421
• DOI: 10.2298/JSC0909953B

Batch sorption experiments were performed for the removal of chromium(III) ions from aqueous solutions using Romanian Sphagnum moss peat (untreated and treated with NaCl solution) as sorbent. In order to establish the best conditions for the sorption of chromium(III), the influence of initial pH, contact time, peat dose and metal ion concentration was investigated. The Freundlich, Langmuir and Dubinin-Radushkevich models were applied to describe the sorption isotherms and to calculate its constants. The experimental data fitted well to the Langmuir model with a maximum sorption capacity of 18.6 mg Cr(III)/g of peat. The mean free energy of sorption suggests that the binding of Cr(III) on peat occurred through an ion exchange mechanism. The kinetic data evaluated by pseudo-first order and pseudo-second order kinetic models showed that the sorption of chromium onto the peat followed a pseudo-second order rate equation. The chromium(III) could be easily eluted from the loaded peat using 0.10 M HCl and the peat may be reused in several sorption/ desorption cycles. The experimental results indicated the potential of Sphagnum moss peat for removal of Cr(III) from wastewaters. Izvedena je grupa sorpcionih eksperimenata za uklanjanje jona hroma (III) iz vodenih rastvora pomocu tresetne mahovine Sphagnum sa podrucja Rumunije (netretirane i tretirane rastvorom NaCl) kao sorbentom. U cilju uspostavljanja najpogodnijih uslova za sorpciju hroma(III), ispitivani su uticaji pH, vremena kontakta, kolicine mahovine i koncentracije jona. Primenjeni su modeli Frojndliha (Freundlich), Lengmira (Langmuir) i Dubinin-Radusevica (Dubinin-Radushkevich) za opis sorpcionih izotermi i za izracunavanje odgovarajucih konstanti. Eksperimentalni rezultati odgovaraju Lengmirovom modelu sa maksimalnim sorpcionim kapacitetom od 18,6 mg Cr(III) po gramu mahovine. Vrednost srednje energije sorpcije ukazuje na to da se Cr(III) vezuje za mahovinu po mehanizmu izmene jona. Kineticki podaci, dobijeni na osnovu pseudo-prvog i pseudo-drugog kinetickog modela, pokazuju da proces sorpcije hroma na mahovini sledi zakon brzine pseudo-drugog reda. Sorbovani hrom(III) lako moze biti odvojen od mahovine ispirannjem rastvorom 0,10 M HCl, dok se ista mahovina moze koristiti u nekoliko ciklusa sorpcija/desorpcije. Eksperimentalni rezultati ukazuju na to da tresetna mahovina Sphagnum ima potencijal za primenu uklanjanja Cr(III) iz otpadnih voda.