Remediation of Heavy Metals from Galvanic Wastewater Using Cow Bone Char as Low Cost Adsorbent

Abstract

The adhesion of metal ions from wastewater to surface of a material in an adsorption process had proven to be effective for remediation of wastewater before discharge. There is a growing demand to utilize alternative low-cost adsorbents for the removal of heavy metals from galvanic wastewater in most developing countries. Cow bones are cheap, readily available and can be sourced locally from slaughterhouses and abattoir. Therefore, their use as an alternative adsorbent for remediation of galvanic wastewater had to be assessed. In this study, the efficacy of cow bone char (CBC) was assessed for simultaneous heavy metal ions removal from real life galvanic wastewater in a competitive adsorption process. The galvanic wastewater was characterized using atomic adsorption spectrophotometry while the CBC was characterized using X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR). Batch experiment was performed to determine the effect of adsorbent dose, contact time and agitation speed on the removal efficiency of heavy metal ions from the galvanized wastewater. The concentrations of Mn2+, Fe2+, Zn2+, Pb2+ and Cr2+ in the raw wastewater exceeded the WHO and EPA standards. The adsorbent revealed a significant distribution of well-developed porous, rough surfaces with cracks characterized by different functional groups for the efficient adsorption process. The optimum adsorbent dose for all the metal ions was 0.04 g/100 mL at an optimum contact time of 60 minutes except for Fe2+ with optimum contact time of 20 minutes, and agitation speed of 150 rpm. The maximum metal removal efficiencies obtained for Mn2+, Fe2+, Zn2+, Pb2+ and Cr2were 99.7%, 100%, 99%, 90% and 85% +, respectively. The average adsorption capacity for Mn2+, Fe2+, Zn2+, Pb2+ and Cr2+were 0.44 mg/g, 26.7 mg/g, 78.5 mg/g, 0.133 mg/g for and 10.36 mg/g, respectively. CBC offers efficient and cost-effective removal of selected metal ions from galvanized wastewater.

Keywords

• adsorption
• cow bone
• galvanized wastewater
• heavy metals
• removal efficiency