Removal of bentazon and metalaxyl pesticides from aqueous solutions by adsorption using almond and chestnut shells: Optimization by experimental design, research of adsorption kinetics and isotherms

Pesticides are chemicals that have been used since 1940s for raising the food quality and minimize the loss of agricultural products against some of the problems in the agricultural industry such as weeds, insects and funguses. Due to its easy application and effectiveness in a short period of time, the usage of pesticides has been increased with the increase of world population which leads to nutritional requirements. Because of intensive and insensible usage of pesticides, they contaminate to the water resources in the consequences of run-off and percolation from agriculture field and also that careless and insensible disposal of wastewaters to environment by pesticide producers. Pesticide concentrations of wastewaters from those industries can sometimes reach up to high and dangerous levels such as almost 500 mg/L. There are a lot of methods for removal of pollutant wastes from aqueous solutions. Among those methods, adsorption is the most used process due to its high efficiency and ease of application. The adsorbent in the adsorption processes are required to be cheap and effective. Actived carbon is the most used adsorbent in the adsorption processes. Although actived carbon has very high surface area and high adsorption capacity for many organic pollutants, commercial activated carbon is very expensive. Therefore, finding out promising and cheap alternative adsorbents is an important subject that attracts researchers' intention. In the present study, removal of Bentazon and Metalaxyl pesticides from aqueous solutions by adsorption method is aimed. Agricultural wastes almond and chestnut shells are used as alternative adsobent for removal of the pesticides from aqueous solutions. By using Box-Behnken Experimental Design, affects of pH (2.0, 3.5 and 5.0), adsorbent concentration (1.0, 2.0 and 3.0 g/50 ml), pesticide concentration (25, 50 and 75 mg/L) and adsorption time (40, 80 and 120 minutes) on adsorption were investigated and optimizations of the adsorption processes were performed. Also, modelling studies were performed and the most suitable adsorption kinetic models and adsorption isotherm models were determined for each pesticide and adsorbent used.