Evaluating the Adsorption Potential of Alachlor and Its Subsequent Removal from Soils via Activated Carbon

Alachlor, a globally used aniline herbicide, has great agronomic interest for controlling the development of broadleaved weeds and grasses. This research aspires to evaluate the sorption attributes of Alachlor through batch equilibrium method and its successive removal through biomass based activated carbon prepared from Sawdust (Cedrus deodara). Six soil samples were collected from selected regions of Pakistan to assess the adsorption and removal phenomena. Adsorption capacity for Alachlor varied in soils depending upon their physicochemical properties. Adsorption coefficient (K-d) values ranged from 12 to 31 mu g ml(-1) with the highest K-d value observed in soil sample with highest organic content (1.4%) and least pH (5.62). The Gibbs free energy values ranged from -17 to -20kJ mol(-1) proposing physio-sorption and exothermic interaction with soils. Values of R-2 (0.96-0.99) exhibited the best fit to linear adsorption model. Adsorption coefficient displayed a negative correlation (r = -0.97) with soil pH and positive correlation with organic matter (r = 0.87). The effect of contact time and pesticide concentration on the removal efficiency by activated carbon was investigated. The highest removal percentages observed through activated carbon were 66% and 64% at concentrations of 5 and 7.5ppm respectively. Activated carbon from sawdust (Cedrus deodara) was investigated as a suitable adsorbent for the removal of Alachor from selected soils. Biomass based activated carbon can prove to be an effective and a sustainable mean to remove pesticides from soil.