Comparative Study on the Removal of Various Phenoxyalkanoic Acid Herbicides from Aqueous Solutions on Polycaprolactone and Activated Carbon

The removal of various phenoxyalkanoic acid herbicides as single solutes (2,4-D; 2,4-DP; 2,4-DB; 2,4,5-T; MCPA) from aqueous solutions were studied by using biodegradable poly(e-caprolactone) (PCL). A comparative study was achieved by using powdered and granular activated carbon as an adsorbent in a batch system. The equilibrium was studied at 25, 35, and 45 degrees C. The results were correlated by using Freundlich Langmuir, Temkin, Redlich-Peterson, and Sips equations. To determine the best fit isotherm, three error analysis methods were used to evaluate the data: correlation coefficient (R-2), residual root-mean-square error, and normalized deviation (Delta Q). The results show that all the isotherm models provide an appropriate fitting to the experimental data for the adsorption onto PCL. Adsorption of the studied herbicides onto granular activated carbon, powdered activated carbon, and poly(e-caprolactone) decreased in the order of 2,4-DB > 2,4,5-T > 2,4-DP > 2,4-D > MCPA. The thermodynamic parameters (Delta G degrees, Delta H degrees, Delta S degrees) for the adsorption process were calculated, and the results suggest that the nature of adsorption is endothermic and the process is spontaneous and favorable. Overall the results show that biodegradable poly(e-caprolactone) is a promising alternative adsorbent to be used in water treatment. DOI: 10.1061/(ASCE)EE.1943-7870.0000452. (C) 2011 American Society of Civil Engineers.