Sustainable colour, sulfate and phosphate removal from vegetable oil refinery wastewater using snail shell waste extracted-chitin-chitosan: Equilibrium studies and toxicity assessment of used adsorbents

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Direct discharged of vegetable oil refinery wastewater without treatment can cause severe environmental pollution, corrosion and clogging of pipes. This work is aimed at investigating the use of snail shell extracted chitin and chitosan fortified with alum in removing colour, sulfate and phosphate from vegetable oil refinery waste water, monitoring the pH, and testing the toxicity of the used materials on the growth performance of maize. Chitin and chitosan with good adsorbent properties were produced from snail shells. The spent chitin/alum and chitosan/alum were recycled and their toxicities on the growth performance of maize tested. The studied wastewater had pH of 10.40, sulfate and phosphate concentrations of 3100 and 1561.3 mg/L respectively. Maximum removal capacities for sulfate and phosphate of 842.54 and 728.07 mg/g were respectively obtained for chitin, and respectively 934.97 and 728.00 mg/L for chitosan against colour removal of 0.96 and 0.95 Absorbance/g respectively on chitin and chitosan. Nearly 100% of colour and phosphate were removed by chitin and chitosan systems for all tested parameters against a maximum of 84% for sulfate by chitosan at pH 10 and 80% for chitin at pH 4. From Pseudo-second order kinetics, phosphate and sulfate removal were faster on chitin than chitosan while colour removal was faster on chitosan than chitin. Recycled adsorbents enhanced maize germination and survival than the control where they were absent. Tested adsorbents are effective in improving quality of studied effluent, requiring no electricity and can be used as fertilizers, ensuring clean environment and generation of more revenue