Experimental evidence from the literature is presented to demonstrate that adsorption of chemical substances in soils and related materials is significantly influenced by competition from other adsorbing chemicals. Both organic and inorganic ions are capable of competing for adsorption sites on soils. Potential competing chemical species include: phosphate, sulfate, selenite, molybdate, arsenate, bicarbonate, oxalate, citrate, different phenols, and polygalacturonate among anions, and calcium, lead, magnesium, sodium, and zinc among cations. Competitive adsorption occurs on a wide variety of soils, on such clay minerals as kaolinite, montmorillonite, haematite, goethite, gibbsite, pseudoboehmite, etc., and on such other materials as activated carbon. Although the diversity of experimental conditions and methods to study competitive adsorption is great, competition is clearly influenced by factors such as pH, solution concentration, and nature of the competing species. Results of some experimental studies on the effects of competition on the ion distributions between the solution and solid (adsorbed) phases are qualitatively similar to those expected from theoretical models and simulations presented in previous papers. The evaluation of the models was incomplete because the adsorption data for all the competing species were not available. Several quantitative comparisons between experimental isotherms and the theoretical predictions showed that the competitive adsorption models satisfactorily describe competition.
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Murali et al. (1983) studied this question.