Adsorption characteristics of Cu and Zn onto various size fractions of aggregates from red paddy soil

• Published in: Journal of hazardous materials Vol. 264; pp. 176 - 183
• Main Authors: Huang, Bin, Li, Zhongwu, Huang, Jinquan, Guo, Liang, Nie, Xiaodong, Wang, Yan, Zhang, Yan, Zeng, Guangming
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.01.2014; Elsevier
• Subjects: Adsorption; Adsorption characteristics; Applied sciences; Chemical engineering; Copper - chemistry; Exact sciences and technology; Heavy metals; Hydrogen-Ion Concentration; Kinetics; Oryza; Pollution; Red paddy soil; Soil aggregates; Soil Pollutants - chemistry; Thermodynamics; Zinc - chemistry; Red paddy soil; AFx; V/V; Adsorption characteristics; Heavy metals; Soil aggregates; Second order; Particle size; Organic matter; Adsorption site; Adsorption capacity; Desorption; Modeling; Heavy metal; Sorption; Adsorption; Trend analysis; pH; Agriculture; Paddy field; Kinetics; Aggregate; AF(x); accumulation factor; volume per volume
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2013.10.074

•The clay-size aggregate showed faster adsorption rate and larger capacity.•pH effect the adsorption and desorption of various aggregates at different levels.•The clay-size aggregate may accumulate metals more easily in natural environment.•Metal speciation in the clay-size aggregates appeared to be more stable. Soil aggregate is the basic structure unit of soils and the ability of various size fractions are different in the aspect of adsorbing and transferring heavy metals in the environment. In this study, bulk soil from red paddy field was partitioned into four aggregate-size fractions and their adsorption characteristics for Cu and Zn were studied. Our results showed that: Pseudo-second order model was more successful to fit the adsorption process in the kinetic experiments and the isothermal experiments data can be described well with the Freundlich model as a whole. Due to higher contents in organic matter, CEC and free iron oxide, the <0.002mm fraction was found to have the highest initial sorption rate and maximum adsorption capacity. The adsorption amount of metals increased as the increasing of pH and the percentage of adsorbed metal susceptible to desorption into 0.01M NaNO3 was greater for Zn than for Cu, while their variation trends were quite opposite. More specific adsorption sites in the <0.002mm fraction lead to more desorption amount for this particle size of soil at low pH condition. After 60 days of incubation, Cu and Zn were observed to enrich in the clay-size aggregates with fractions more stable than other particles.