Removal of selected pesticides from water using granular activated carbon

Abstract

Abstract Pesticides are intensively used for the protection of field crops, orchards and vineyards, but they are also used in the removal of undesirable stands on non-agricultural land (railway embankments, playgrounds, handling areas, etc.), in water management (in coastal management, destruction of growths in irrigation canals), in forestry, etc. Regular application of pesticides increases their content in the aquatic environment and agricultural products. Their occurrence in water is relatively common and it follows that these substances are used in large quantities. Residues of these substances can persist in soils for 2 to 12 weeks. Due to their good solubility in water, they are easily transported from the soil to aquifers. Several methods can be used to remove pesticides from water, e.g., coagulation, filtration, precipitation, ozonation, adsorption, ion exchange, nanofiltration, reverse osmosis and advanced oxidation processes. Their effectiveness varies considerably and depends mainly on the chemical nature of the pesticide being removed. This article studies adsorption on two granular activated carbons Filtrasorb 400 and Norit 1240. Mixture of the pesticide standards (acetochlor, alachlor, dimethachlor, propachlor, metazachlor and metolachlor) was added to drinking water with concentration of approximately 1 µg/L. The experiments were performed in the glass bottles with the volume of 200 mL of water. The granular activated carbons (200 mg) were added to the bottles. Subsequently these bottles were regularly stirred, and the samples were taken out at times 0, 30, 60, 90, 120, 180, 240 and 360 minutes. Samples were taken by pipette into the 40 ml glass vials with added thiosulphate for preservation. Analyses of target pesticides were performed in laboratories of ALS Czech Republic in Prague. LC-MS using the internal standard method was used to determine chlorinated pesticides in water samples. The adsorption efficiency of pesticides removal and the adsorption capacity of granular activated carbon depends on the time of contact of water with the material. The results showed that the efficiency of selected pesticides removal and adsorption capacity for two granular activated carbons used varied. Filtrasorb F400 proved to be a better sorption material than Norit 1240. The efficiency of this material ranged from 18 to 60%, while the efficiency of Norit 1240 was significantly lower. Adsorption capacity of activated carbons for selected pesticides and reaction kinetics of 0th, 1st, 2nd and 3rd order was also studied.