• journal_title：Clays and Clay Minerals
• Contributor：Maria Jose Carrizosa ; Maria del Carmen Hermosin ; William C. Koskinen ; Juan Cornejo
• Publisher：Clay Minerals Society
• Date：2004-
• Format：text/html
• Language：en
• Identifier：10.1346/CCMN.2004.0520510
• journal_abbrev：Clays and Clay Minerals
• issn：0009-8604
• volume：52
• issue：5
• firstpage：643
• section：Articles

The sorption of two sulfonylurea herbicides (SU), metsulfuron methyl and nicosulfuron, on pure clays and organoclays was investigated. Three clays (Arizona smectite, SAz-1, Wyoming smectite, SWy-2, and hectorite, SHCa-1), were treated with amounts of octadecylammonium (ODA) or dioctadecyldimethylammonium (DODMA) cations equal to ~50 and 100% of the clays’ cation exchange capacity (CEC). Sorption isotherms were fitted to the Freundlich equation. While no measurable sorption was found on the pure clays (K_f = 0), organoclays prepared using both primary and quaternary amines were effective as SU sorbents. The metsulfuron methyl K_f values ranged between 196 and 1498 μmol¹⁻ kg⁻¹ L^1/n, and K_f values for nicosulfuron, which were lower than those of metsulfuron methyl, ranged from 35 to 198 μmol^1−1/n kg⁻¹ L^1/n. As shown by sorption coefficients, K_d and K_OC, SWy-2 treated with DODMA at ~100% of the CEC was the most effective sorbent for metsulfuron, K_d = 684 L kg⁻¹ and K_OC = 2138 L kg⁻¹. For nicosulfuron the most effective sorbent was SAz-1 with ODA at ~ 50% of the CEC (K_d = 147 L kg⁻¹ and K_OC = 1233 L kg⁻¹). In contrast to other weak-acid herbicides, such as phenoxy and picolinic acids, no clear relationships were found between sorption and layer charge, organic carbon content, and basal spacing of the organoclays for both sulfonylurea herbicides. Sorption of both herbicides on organoclays was assumed to involve hydrophobic and polar interactions for which the availability of interlayer room between organocations was a very important factor.