Non-competitive and competitive adsorption of cadmium and zinc by nano-iron and titanium oxides from aqueous solution

• Published in: International journal of environmental science and technology (Tehran) Vol. 19; no. 7; pp. 6375 - 6388
• Main Authors: Sepehr, E., Piri, M., Ahmadi, F., Gasemi, M., Sharifmand, M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2022
• Subjects: Aquatic Pollution; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Science and Engineering; Original Paper; Soil Science & Conservation; Waste Water Technology; Water Management; Water Pollution Control; Titanium oxide nanoparticles; Competitive adsorption; Isotherm models; Iron oxide nanoparticles; Ionic strength
• ISSN: 1735-1472; 1735-2630
• DOI: 10.1007/s13762-021-03833-x

Water pollution by heavy metals is a main global issue in developed communities due to human and industrial operations. This study was aimed to assess the efficiency of nano-TiO 2 and Fe 2 O 3 adsorbents for removal of cadmium and zinc in single- and double-ion aqueous solutions. The effects of pH (cadmium = 4, 6, and 7, zinc = 4, 5, and 6), background electrolyte type (NaNO 3 and Ca (NO 3 ) 2 ), and ionic strength (0.03 and 0.1 M) were studied at the batch single- and binary-adsorption (50 and 100 mg L –1 ) experiments according to standard experimental methods. The equilibrium data were fitted with the Freundlich (R 2  = 0.92–1), Langmuir (R 2  = 0.83–0.99), Temkin (R 2  = 0.75–0.99), and Dubinin–Radushkevich (R 2  = 0.64–0.99) isotherm models. All sorption parameters in models for the sorption of cadmium and zinc by nano-adsorbents decreased by increasing ionic strength from 0.03 to 0.1 M, but pH had an inverse effect. The Freundlich sorption capacity of TiO 2 and Fe 2 O 3 nano-adsorbents was found to be 1.32 and 1.18 (mg 1–1/ n L 1/ n g –1 ) for cadmium and 1.23 and 1.03 for zinc in non-competitive adsorption system and 0.56 and 0.45 for cadmium and 0.60 and 0.37 for zinc in competitive adsorption system, respectively. The E-values of the Dubinin–Radushkevich model (E < 8) and negative Gibbs free energy (∆G 0 ) values demonstrated the physical and spontaneous sorption nature of metals onto TiO 2 and Fe 2 O 3 nanoparticles. In conclusion, the adsorption of cadmium by studied nanoparticles in the presence of zinc showed greater efficacy than that of vice versa.