Adsorption of Pesticides onto Quartz, Calcite, Kaolinite, and α‐Alumina

Abstract

The fate of pesticides in aquifers is influenced by the small but not insignificant adsorption of pesticides to mineral surfaces. Batch experiments with five pesticides and four minerals were conducted to quantify the contributions to adsorption from different mineral surfaces and compare adsorption characteristics of selected pesticides. Investigated mineral phases included quartz, calcite, kaolinite, and alpha-alumina. Selected pesticides comprised atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea)], mecoprop [(RS)-2-(4-chloro-2-methylphenoxy)propionic acid], 2,4-D (2,4-dichlorophenoxyacetic acid), and bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4-(3H)-one 2,2-dioxide]. Specific surface area and mineral surface charge proved to be important for the adsorption of these pesticides. Detectable adsorption of the anionic pesticides (mecoprop, 2,4-D, and bentazone) was only measured when positive sites were present on the mineral surface. However, when CaCl2 was added as an electrolyte, a detectable adsorption of mecoprop and 2,4-D was also measured on kaolinite (which exhibits a negative surface charge), probably due to formation of Ca-pesticide--surface complexes. Adsorption of the uncharged pesticides (atrazine and isoproturon) was detected only on kaolinite. The lack of adsorption on alpha-alumina indicates that the uncharged pesticides have a greater affinity for the silanol surface sites (=SiOH) than for the aluminol surface sites (=AlOH) in kaolinite. No measurable effect of ionic strength was found for the uncharged pesticides. The results indicate that quartz and calcite play a smaller role than clay minerals.

Performance Evaluation of Waste Activated Carbon on Atrazine Removal from Contaminated Water

“…[1] Wood charcoal proved to be an effective low-cost adsorbent for the removal of lindane [2] and endosalfan [3] from the water environment. Recent studies on atrazine adsorption on iron oxides, [4] Quartz, Calcite, Kaolinite, and α-alumina [5] showed that only Kaolinite was suitable for the adsorption of atrazine.…”

Retention characteristics of acetochlor in soils collected from different depths in relation to soil properties (Žitný ostrov area, SW Slovakia)

“…However, positive influence of non-crystalline to poorly crystalline Al oxides on acetochlor sorption should be highly questionable due to positive significant relationship between Al o and TOC (Table 3). Unfortunately, there are no studies regarding the adsorption of chloroacetanilides onto Al oxides, but Clausen et al (2001) demonstrated that the uncharged herbicides like isoproturon and atrazine did not adsorb on the Al-surfaces of α-alumina.…”

Cargas superficiais da fração argila de solos influenciadas pela vinhaça e fósforo

“…Hematita inicialmente apresentou potencial zeta de +20 mV, permanecendo positivamente carregada até a adição inicial de P de 0,16 mM, tornando-se negativa (-20 mV) com a dose de 0,32 mM, alcançando -25 mV na maior dose de P. Gibbsita, inicialmente com potencial de +16 mV, tornou-se negativa (-2,9 mV) com a adição inicial de P de 0,064 mM, alcançando -13 mV na maior dose (1,61 mM). Considerando-se a mesma condição de pH (4,5), os resultados aqui encontrados foram semelhantes aos obtidos por Giaveno et al. 21 O LVdf inicialmente (controle) apresentou potencial zeta de aproximadamente + 13 mV, tornando-se negativo (-4 mV) com a dose inicial de P utilizada (0,08 mM), alcançando -11 mV com a maior dose (2,56 mM) (Figura 1).…”

“…As cargas na superfície das partículas dos solos estão relacionadas aos fenômenos de superfície, como a dispersão/floculação, 1,2 capacidade de troca de cátions e de ânions, 3 adsorção de pesticidas 4 e de metais pesados. 5 As cargas do solo podem ser do tipo permanente, quando originadas de substituição isomórfica na formação dos minerais, principalmente da fração argila, ou dependentes do pH do meio (variáveis), 6,7 sendo essas últimas comuns em solos tropicais altamente intemperizados ricos em óxidos de ferro e de alumínio.…”