El pretratamiento con K2HPO4 mejora significativamente la capacidad de biosorción de Co2+ de Lemna gibba

Abstract

Since divalent cobalt [Co2+] in wastewater is highly toxic, it must be removed before dumping the water into the environment. The aim of this study was to examine the biosorption of Co2+ by Lemna gibba (LG) after pretreatment with various compounds to improve its biosorption capacity. Of the original pretreatments, K2HPO4 (0.1 M) produced the best biosorption capacity of Co2+ by LG (31.21 ± 0.29 mg g-1 vs 18.87 ± 0.19 mg g-1 for the untreated control). Subsequently, the optimal concentration (0.3 M) of K2HPO4 was found (the pretreatment herein denominated PLG), showing a biosorption capacity of 40.13 ± 0.18 mg g-1 at pH 7.0. The pseudo-second order model most adequately fit the experimental kinetics. According to the proximate chemical analysis, the pretreatment enhanced the biosorption capacity (PLG vs LG) by improving sorption site availability through the elimination of salts, and by increasing the negative charge of the plant cell surface (from -26 to -35 mV), thus favoring the approach of positively charged Co2+. The ATR-FTIR analysis of PLG demonstrated that its hydroxyl, carboxyl, amide and amine groups importantly contributed to Co2+removal. Thus, PLG is a promising biosorbent material for Co2+ removal from aqueous solutions.