Application of Spent Castor Oil Seeds Based Nano Biochar in Groundwater Treatment for Removal of Heavy Metals

Groundwater is water stored in underground layers called aquifers and accounts for 30% of the freshwater. In recent years due to climate change effects, industrial and agricultural activities there has been more extraction of groundwater for domestic use leading to increased groundwater pollution including toxic metals such as lead (Pb), cadmium (Cd) and copper (Cu), hydrocarbons, nanoparticles and microplastics. Castor is an edible oilseed crop which produces seeds that contain about 50% oil making it one of the highest yielding crops. After oil extraction the spent seeds contain about 45-55% carbon making them suitable for nano biochar production. The main objective of this study was to investigate the application of spent castor oil seeds based nanobiochar in groundwater treatment for contaminants removal. The study involved characterisation of spent castor oil seeds, production of nano biochar through pyrolysis, its characterisation and application in groundwater treatment. The produced nano biochar was applied to contaminated groundwater under controlled conditions of pH 7 and contact time of 20 hours to measure its adsorption effectiveness For production of nano biochar, firstly biochar has to was produced by slow pyrolysis of the spent castor oil seeds at a temperature of ＜700℃ and a heating rate of 1-100℃/min. Size reduction through grinding produced nano biochar upto 1.0-1.5nm  in size and an increased surface area of 800-1000 m2/g. Application of nano biochar removed 90% of Pb, Cd and Cu ions in contaminated groundwater through the adsorption process.  The results showed that spent castor oil based nano biochar has physical and chemical properties that enhance the treatment of groundwater.