Adsorption−Desorption Studies of Selected Herbicides in Soil−Fly Ash Mixtures

• Published in: Journal of agricultural and food chemistry Vol. 48; no. 10; pp. 4780 - 4790
• Main Authors: Konstantinou, I. K, Albanis, T. A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.10.2000
• Subjects: Adsorption; Agronomy. Soil science and plant productions; Applied sciences; Biological and medical sciences; Biological and physicochemical properties of pollutants. Interaction in the soil; Carbon - chemistry; Chemical control; Chemical Phenomena; Chemistry, Physical; Coal; Coal Ash; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Herbicides - chemistry; Industrial Waste; Parasitic plants. Weeds; Particulate Matter; Phytopathology. Animal pests. Plant and forest protection; Pollution; Soil - analysis; Soil and sediments pollution; Soil and water pollution; Soil science; Solubility; Thermodynamics; Weeds; Treatment efficiency; Pesticides; Immobilization; Desorption; Soil pollution; Herbicide; Dose activity relation; Fly ash; Soils; Adsorption; Triazine derivatives; Prometryn; Carbamate; Comparative study; Atrazine
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf0003606

Fly ash and soil mixtures with a range of fly ash content from 0 to 100% were used to study the adsorption and desorption of herbicides atrazine, propazine, prometryne, propanil, and molinate in batch experiments. The isotherms shapes according to Giles classification (Giles et al., 1960) were S, L, and H as the substrate changed from sandy clay loam (SCL) to fly ash, depending on the percent of fly ash in the mixture. The adsorption isotherms fit the Freundlich equation x/m = K f C 1/ n . The K f values increase with the increase of the fly ash content. The mean percent amounts of herbicides, for a range of concentration 1−20 mg L-1, adsorbed on the soil were 21.9% for atrazine, 50.7% for propazine, 29.04% for prometryne, 43.14% for molinate, 31.35% for propachlor, and 46.34% for propanil. Mass balance estimations show that the adsorbed amounts of the herbicides increase along with the fly ash content in the sorbent mixture and reach the 99% in the “pure” fly ash. In contrast, the amounts desorbed with water decrease as the fly ash content increases. The n values ranged from 0.82 to 3.05 indicating that the carbon content of fly ash plays a significant role during the sorption process and an increase of heterogenity of solid substrate. The increase of the amounts desorbed with acetone indicates that the sorption of organic compounds onto fly ash is believed to occur principally via the weak induction forces of London or dispersion forces which are characteristic of the physical adsorption process. The results of this research demonstrate that the fly ash shows a significant capacity for adsorption of organic compounds from aqueous solution. Keywords: Adsorption−desorption, herbicides, soil−fly ash mixtures