Pesticides’ low-cost removal from polluted groundwater using charcoal from “Salix mucronata” trees activated by gold nitrate

Abstract

Used pesticides result in soil pollution, which potentially seep into groundwater, posing risks to human and animal health. The current study examines the use of a new cheap material for removing four commonly used pesticides from polluted groundwater before use for drinking. These pesticides are Malathion, Methomyl, Abamectin, and Thiamethoxam. Activated charcoal obtained from the trunk of “Salix mucronata” trees is introduced for removing these pesticides by surface adsorption. Activation treatment using gold-nitrate solution is introduced to enhance the charcoal adsorption capacity, because removal of pesticides is difficult due to their large-sized molecules and lack of obvious surface electrostatic charges. Physical and chemical properties of the studied pesticides and the activated charcoal were determined. Batch experiments tested the effects of solution pH, contact time, dose of charcoal, and initial concentrations on the charcoal adsorption capacity. Langmuir adsorption linear isotherm test was done to use for the prediction of adsorption behavior. Fixed-bed column experiments tested clean-up of polluted water using charcoal filter under steady flow. Gold-nitrate activated charcoal adsorption capacities were almost three times higher than other charcoals for the same pesticides at the same initial concentrations. Maximum adsorption capacities achieved in the current study were 16.17, 14.59, 9.55, and 8.99 mg/g, respectively, at the initial concentrations of 50.0 mg/l. Meanwhile, treatment times in steady-flow fixed-bed columns were much lower compared to other studies. Preparation cost of gold-nitrate activated charcoal in the current study was lower than other adsorbents. The charcoal introduced in this study is recommended for use in low-cost removal of pesticides from polluted groundwater on the national scale, including small treatment units for rural communities with limited facilities.

Keywords

• Wastewater treatment
• polluted groundwater
• agricultural pesticides
• adsorption
• activated charcoal/carbon