Removal of heavy metals using sorbents derived from bark

Abstract

The purpose of this study was to examine the sorption properties of low-cost sorbents derived from bark for heavy metals such as copper and cadmium at different pH and ionic strength conditions. Three different bark-derived sorbents such as untreated, acid treated, and alkaline treated barks were prepared. The acid treated and alkali treated barks were obtained through chemical treatments using 0.1 HCl and 0.1 NaOH solutions, respectively. Morphology, elemental composition, and specific surface area of different bark-derived sorbents were characterized by SEM (Scanning Electron Microscopy), EDS (Energy-dispersive X-ray spectroscopy) and BET (Brunauer-Emmett-Teller) specific surface area measurements, respectively. Batch isotherm tests were carried out to examine the sorption properties of bark-derived sorbents. The results showed that alkali treated bark had high affinity for both copper and cadmium. At pH 7.0 sorption capacity of alkali treated bark for copper (1.43 mg/g) was greater than untreated and acid treated barks, which corresponded to a removal efficiency of around 95%. Also, sorption capacity of alkali treated bark for cadmium was greater than the other bark-derived sorbents, which corresponded to removal efficiency of around ~ 98.5%. In case of pH effect, sorption affinity of untreated bark for both copper and cadmium increased with the increase of pH. On the other hand, for ionic strength effect, sorption affinities of three different bark-derived sorbents for copper decreased with increase of ionic strength. Therefore, the alkali treated bark could be a cost-effective sorbent for the removal of heavy metals from water and wastewater.