Adsorption of Highly Soluble Herbicides from Water Using Activated Carbon and Hypercrosslinked Polymers

Abstract

Adsorption of water-soluble herbicides, namely benazolin, bentazone, imazapyr and triclopyr, has been investigated using commercial Chemviron F-400 activated carbon and Purolite MN-200 hypercrosslinked polymer. Batch adsorption isotherms at pH 3 and 10 show that adsorption of water-soluble herbicides is significantly greater on F-400 than MN-200. Rapid small-scale mini-column adsorption studies of each herbicide on F-400 and MN-200 have also been performed. For Chemviron F-400, the breakthrough of each herbicide at the EU limit of 0.1 μg l-1 is as follows: imazapyr (80,000 BV), bentazone (105,000 BV), benazolin (140,000 BV) and triclopyr (160,000 BV). These experiments operated at an emptybed- contact-time (EBCT) of 2.3 secondswith feed water containing 20 μg l-1 of each herbicide in the absence of natural organic matter. MN-200 is less effective in removing these herbicides from contaminated water under similar conditions. The presence of fulvic acid in the feed water significantly diminishes the uptake of each herbicide for F-400 and MN-200. Low temperature regeneration of Chemviron F-400 activated carbon and Purolite MN-200 hypercrosslinked polymer was achieved using ethanol solution at 50°C and pH 12. Virtually complete regeneration is achieved with MN-200 in 10 BV. Approximately 200 BV of eluent is required with F-400 and the regenerant efficiencies are about 100%for benazolin and triclopyr and about 40-50% for bentazone and imazapyr after two cycles.