Adsorption of 15 different pesticides on untreated and phosphoric acid treated biochar and charcoal from water

In the present study, the adsorption of a mixture of 15 different pesticides (with individual pesticide concentrations of 400 μg/l) from water by untreated and treated (using phosphoric acid) biochars and charcoal has been studied. Solid–water distribution coefficients (Kd) were used to compare the pesticide adsorption abilities of the tested adsorbents. The phosphoric acid-treated and untreated biochar and charcoal were characterized by CHN-elemental analysis, ash content, adsorbent pH in solution measurements, surface area (BET), scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. Pesticide residual concentration was analyzed using liquid chromatography–tandem mass spectrometry (LC–MS/MS). The results showed that the adsorption of these pesticides from water using biochars was higher than that using charcoal. The effect of chemical treatment using phosphoric acid on biochars is also higher than in charcoal. Treated rice straw biochar takes only 2 h (adsorption contact time) to reduce the individual pesticide concentration in water (pH 7) to ≤0.005 μg/l with the exception of oxamyl, which was reduced to ≤0.068 μg/l after 24 h. Oxamyl can be easily removed from water by its degradation under the alkaline effect of untreated biochar.