Removal of Heavy Metals and Pharmaceuticals From Contaminated Water Using Waste Sludge – Kinetics and Mechanisms

Abstract

The aim of this study was to investigate the adsorption of heavy metals (CrTOT, Ni2+, Cu2+, and Zn2+) in wastewater originated from galvanization process and pharmaceuticals (ciprofloxacin and dexamethasone) in aqueous solutions on waste sludge. To get the insight in the adsorption process, the adsorption kinetics and mechanisms are described. The physico‐chemical properties of the waste sludge were determined by scanning electron microscopy coupled with energy dispersive spectroscopy, X‐ray diffraction technique, energy dispersion X‐ray spectrometry, surface area and gas adsorption porosimetry, and laser diffraction. The adsorption on waste sludge was performed as batch tests and the concentration of heavy metals and pharmaceuticals was monitored by atomic absorption spectrometry and UV/Vis spectrophotometry, respectively. The rates of pharmaceuticals adsorption dependent on different initial concentration were explained. The kinetics of heavy metal ions and pharmaceuticals adsorption on the sludge was analyzed using four different models. The pseudo second‐order model assuming chemical adsorption as the rate limiting process showed the best agreement. Furthermore, the results revealed that the adsorption involves complex processes, including film diffusion and intraparticle diffusion. The investigated industrial waste sludge is a promising non‐hazardous and a low cost sorbent with relatively high surface area which can be used for removal of heavy metal ions (CrTOT, Ni2+, Cu2+, and Zn2+), and pharmaceuticals (ciprofloxacin and dexamethasone) from wastewater.