US EPA

6333092 

Journal Article 

Adsorption of microcystin-LR onto kaolinite, illite and montmorillonite 

Liu, YL; Walker, HW; Lenhart, JJ 

2019 

Yes 

Chemosphere
ISSN: 0045-6535
EISSN: 1879-1298 

Elsevier Ltd 

220 

696-705 

English 

30611067 

10.1016/j.chemosphere.2018.12.137 

WOS:000458591200077 

In this study, microcystin-LR (MCLR) interactions with three representative silicate clays were studied using equilibrium batch experiments in order to provide insight into the role of clays on determining MCLR fate. The three tested clay minerals (kaolinite, montmorillonite and illite), saturated with sodium or calcium ions, were equilibrated with MCLR across a range of toxin concentrations at pH 5, 7 or 9. The results were fit to Freundlich and linear isotherm models, with the linear isotherm fits deemed most appropriate. In general, adsorption of MCLR was greater in the systems with Ca than in those with Na, however, regardless of the cation present, montmorillonite had the highest adsorption affinity for MCLR. Furthermore, except for Ca-montmorillonite, MCLR adsorption decreased with increasing pH. The pH-dependence of adsorption suggests the polar groups of MCLR, carboxylate associated with the glutamic acid and methylaspartic acid groups and amine associated with the arginine group, were more important in determining MCLR interactions with clays than the nonpolar ADDA group. Increased adsorption in systems enriched with calcium suggests Ca modified the clay interfacial properties and the availability of MCLR groups in a manner that increased MCLR affinity. Overall, the results suggest clays are capable of adsorbing MCLR from the aqueous phase, particularly at low pH and when saturated with Ca2+. 

Clay; Cyanotoxin; Fate; Linear isotherm; Amino acids; Calcium; Carboxylation; Clay; Isotherms; Kaolinite; Silicates; Adsorption affinity; Batch experiments; Ca-montmorillonite; Cyanotoxins; Fate; Interfacial property; Linear isotherms; Toxin concentrations; Adsorption; aluminum silicate; arginine; calcium; carboxylic acid; glutamic acid; illite; inorganic salt; microcystin LR; montmorillonite; sodium; unclassified drug; bentonite; illite; kaolin; microcystin; microcystin LR; mineral; silicate; adsorption; cation; concentration (composition); experimental study; isotherm; kaolin; montmorillonite; pH; toxin; adsorption; Article; chemical interaction; concentration (parameter); controlled study; isotherm; pH; binding site; chemistry; clay; metabolism; Adsorption; Bentonite; Binding Sites; Calcium; Clay; Hydrogen-Ion Concentration; Kaolin; Microcystins; Minerals; Silicates; Sodium