Preliminary study of copper(II) ions removal from wastewater using solid residue obtained by co-pyrolysis of lignite and high density polyethylene mixture

Abstract

In this study the solid residue obtained by the co-pyrolysis of low quality, mineral-rich lignite taken from the Kostolac Basin, Serbia (45.36% of ash; 33.42% of total organic carbon; net calorific value of 9.5 MJ/kg) and high density polyethylene, HDPE (mass ratio, 1:1) at 500 oC was tested as a sorbent for Cu2+ ions, considering that as a coaly-based material, simultaneously enriched in clays, it may have good adsorption properties. Sorption experiments of were performed using 0.5 g of solid co-pyrolysis lignite/HDPE product, as sorbent which was treated with 5 cm3 of model solutions containing ~ 200 times higher concentration of Cu2+ ions (242.60 mg/dm3), in relationship to its maximal allowed content in surface water of bad quality. Model solutions were prepared using corresponding nitrates dissolved in distilled water. Two model solutions were prepared. The first model solution contained individual Cu2+ ions, whereas the second one contained mixture of Cu2+, Pb2+, Co2+ and Cd2+ ions. Concentration of each ion in latter was also ~ 200 times higher than its maximal allowed content in surface water of bad quality. Treatment with distilled water was used as a blank. Concentrations of heavy metal ions in initial model solutions and supernatants obtained after sorption experiments were measured using inductively coupled plasma – optical emission spectrometry. The obtained results indicated very efficient sorption of Cu2+ ions from its individual model solution, attaining 99.96%. The efficiency of Cu2+ ions sorption was also high (99.95%) from model solution, which contained mixture of metal ions. It is important to mention that sorption of other metal ions from model solution mixture was also effective (99.99%, 80.70% and 71.04% for Pb2, Cd2+ and Co2+, respectively). The preliminary results showed promising sorption properties of solid residue obtained by the co-pyrolysis of lignite and HDPE against Cu2+, but also possibly for other heavy metals, particularly, Pb2+ ions.