Removal of Permethrin and Bifenthrin Insecticides from Runoff Water by Activated Carbon Adsorption

Among the hundreds of pesticides and insecticides, pyrethroids-particularly permethrin and bifenthrin, have become very popular due to their high toxicity to insects and low toxicity to humans, leading to extensive use in both agriculture and urban areas. Pyrethroids have no discharge limits because of this, leading to a negative impact on surrounding ecosystems due to their high toxicity to fish and aquatic life. Due to their low solubility and long half-lives, they are prominent in the environment long after application with a high potential for getting transported in runoff water to nearby water bodies. In this study, DSR-C reactivated carbon from Calgon Carbon was tested as an adsorbent for permethrin and bifenthrin from deionized water. Pyrethroid samples were extracted from water by liquid-liquid extraction and analyzed using a UV-vis spectrophotometer. Isotherm data was best represented by the Langmuir model suggesting single-layer adsorption with an adsorption capacity of 149 mg/g for permethrin and 0.822 mg/g for bifenthrin. Permethrin adsorption was studied further in solutions containing 200 mg/L of sulfate and 10 mg/L of nitrogen, phosphorus, and potassium fertilizer nutrients to simulate realistic agricultural runoff conditions. Across all three water matrices used (DI water, 10 mg/L N-P-K, and 200 mg/L sulfate), kinetic data for permethrin adsorption was best represented by the pseudo-second order kinetic model with similar kinetic rates and equilibrium capacities. Isotherm data represented by the Langmuir model resulted in an average adsorption capacity of 155 ± 39 mg/g across three different water matrices. Adsorption with DSR-C is an effective treatment process for permethrin in agricultural runoff water.