Keywords: heavy metal biosorption, onion waste, garlic waste, wastewater treatment, market waste, food canning, heavy metals, effluent decontamination, batch adsorption, remediation cost, biomass
Biosorption of heavy metals by utilising onion and garlic wastes
Onion (Allium cepa L.) and garlic (Allium sativum L.) wastes from market and food canning processes were used for adsorption of Pb2+, Sn2+, Fe2+, Hg2+, As3+ and Cd2+ from multi–component systems at different adsorbent/metal ion ratios. The influence of pH, contact time, temperature and the concentration of adsorbent and adsorbate were studied to optimise the conditions to be utilised on a commercial scale for the decontamination of effluents in a batch adsorption technique. The study was carried out at 50°C and efficiencies were found to be pH dependent. The equilibrium time was 30 minutes and kinetic parameters were calculated using a second order model. The maximum q value was 10.47 ± 0.52 mg g−1 obtained for Pb2+ at an adsorbent loading weight of 0.5 g/100 ml mixed ion solution. Desorption indicates maximum 71% recovery of metal ions, making the remediation process cost effective and reusable. The biomasses were used for removal of heavy metals from both synthetic and industrial effluents and the technique appears industrially applicable and viable.