Low-cost corn cob biochar for pesticides removal from water

This work aimed to study the isotherm and kinetics of adsorption of a mixture of 10 pesticides (viz., atrazine, chlorfenvinphos, chlorpyrifos, cyprodinil, diazinon, dimethoate, diuron, ethion, malathion, and profenofos) on corn cob biochar (CCB) in an aqueous solution. CCB is a low-cost adsorbent produced from pyrolysis at 500 degrees C for 3 h in an oxygen-limited condition. It was characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine the residual pesticide concentration. Adsorption equilibrium and kinetics were investigated by using batch adsorption experiments. The optimized pH, contact time, adsorbent dose, and initial pesticides concentration for the maximum adsorption rates were found to be 3, 60 min, 10 g/L, and 500 mu g/L, respectively. The sorption of all pesticides by CCB was found to enhance by decreasing pH; since the removal percentage of atrazine increased from 57 to 74 % by decreasing the pH from 9 to 3. The Langmuir model represented the adsorption process better than the Freundlich model with R-2 values ranging from 0.957 to 0.999. Adsorption kinetic data were fitted well with the pseudo-first order kinetic model. Accordingly, CCB can be used as an effective low-cost agricultural waste that could be applied for removing pesticide residues from water.