Hybrid Coordination Networks for Removal of Pollutants from Wastewater

The adsorption properties of two coordination polymers, resulting from the reaction of divalent metal (Ca2+ or Co2+) salts with (2-carboxyethyl)(phenyl)phosphinic acid, are presented in this paper. The structural and textural characterization before and after adsorption experiments is presented. The adsorbent materials were prepared using the hydrothermal procedure. The compound Ca[O2P(CH2CH2COOH)(C6H5)](2) (CaCEPPA) has a layered topology, with the phenyl groups oriented into the interlayer space and crystallizes in the monoclinic system. Compound Co-2[(O2P(CH2CH2COO)(C6H5)(H2O)](2)center dot 2H(2)O (CoCEPPA) has a 1D structure composed of zig-zag chains. The adsorption performances of CaCEPPA and CoCEPPA materials were tested in the removal of cadmium and lead from aqueous solutions. The optimum pH of ions adsorption was found to be five for both adsorbent materials. Pseudo-first and second-order kinetic models were used for fitting kinetic experimental data, and Langmuir and Freundlich isotherms were used for modeling the equilibrium experimental data. The pseudo-second-order kinetic model and Langmuir isotherm best described the adsorption of Cd and Pb ions onto the studied materials, judging from the results of the error function (correlation coefficient, sum of square error, chi-square test, and average relative error) analysis. The studied materials present a higher affinity for Cd ions compared with the adsorption capacity developed for the removal of Pb ions from aqueous solutions. CoCEPPA showed the highest adsorption performance in the removal process of metal ions from aqueous solutions compared with CaCEPPA (q(m) = 54.9 mg Cd2+/g of CoCEPPA, q(m) = 36.5 mg Cd2+/g of CaCEPPA).

Automated summary

This paper presents the adsorption properties of two coordination polymers for the removal of cadmium and lead ions from aqueous solutions. The studied materials show a higher affinity for cadmium ions, with CoCEPPA exhibiting the best adsorption performance. Kinetic and equilibrium data were fitted using pseudo-second-order kinetics and Langmuir isotherm, respectively.