Comparative Assessment of the Efficiency of Rice Husk Biochar and Conventional Water Treatment Method to Remove Chlorpyrifos from Pesticide Polluted Water

Nigeria is currently the largest rice producing country in Africa. High volumes of waste such as rice husk are inevitable with high production. Also pesticides used to rid of pests, diseases and improve crop yield find their ways into available surface water that serves domestic purpose. This study therefore determined the efficiency of conventional water treatment procedure for pesticide/pesticide residue removal and evaluated the performance of rice husk-based biochar as adsorbent to remove chlorpyrifos from domestic water supply with a view to manage solid waste (rice husk) for treating pesticide polluted water. Batch adsorption studies were carried out to assess the adsorption efficiency of rice husk biochar (RHB) for chlorpyrifos pesticide removal from surface water. Adsorbent dosage, initial concentration, contact time and dosage were optimized during simulation experiment. RHB and commercial activated carbon (CAC) were used for the removal of chlorpyrifos from surface water sample using the optimum condition from the simulation experiment after which the concentrations were determined using Gas Chromatography with Mass Spectrometry detector. Both Langmuir and Freundlich adsorption isotherms were investigated. RHB gave percentage moisture (5.27±0.94), carbon yield (39.44±0.47), ash (41.96±0.96), fixed carbon (35.24±0.55), volatile matter (35.67±1.01 mg/g), Iodine number (85.57±0.81), surface area (97.20 m2/g), pH (7.90±0.14) and Electrical conductivity (298.8±1.14). Of the elements present in the char, Carbon has the highest percentage of 59.14%. Best adsorption conditions for RHB in this study were 2.8 mg/L initial concentration; 0.8 g of adsorbent dosage; pH of 5 and contact time of 30 min. The data fitted Freundlich than Langmuir model (R2 0.996 and 0.8315 respectively). Percentage removal of chlorpyrifos for CAC and RHB was 93.7±3.96 and 94.5±5.23 respectively for the surface water sample. Results concluded that RHB was efficient for removal of chlorpyrifos present in water and could be used as alternative for CAC in water treatments.