Removal of Cd and Ni Ions from Water Using Biosorbent Based on Corn Residues

Water sources have become unsafe for human consumption, but also for use in agriculture for irrigation or for the food industry. The deteriorating water quality has led to a shortage of drinking water supply. The aim of this study was to examine the possibility of using agricultural waste, specifically corn residues, (corn cob and silk) as a bioadsorbent to remove Ni and Cd ions from water. Experimental results have shown that corn residues (corn cob and corn silk) have a certain potential for use as bioadsorbents. The possibility of application was tested for corn cob and corn silk (corn cob 3.5g and corn silk 1.5g) for metal concentrations of  20, 40, 100 mg/L for corn cob, and 40 mg/L and 100 mg/L for corn silk. The tests were performed at pH 3 and 6 at a contact time to reach equilibrium of 3.5 hours. Adsorption parameters were determined using the Freundlich isotherm. The morphology of biosorbents before and after the adsorption process was monitored to observe differences in the structure of the biosorbents used. The results showed that in the case of Cd2 + ions, with an initial concentration of 100 mg/L the highest removal efficiency was achieved for all samples used, while in the case of Ni2+ ions the highest removal efficiency was achieved at an initial concentration of 40 mg/L for all samples, while the corn silk based of the maize (Zea mays L.) sample proved to be the best for the removal of these ions where the influence of pH has a great influence on the removal efficiency as well as the physico-chemical properties of the metal. Morphological analysis of samples before and after the adsorption process showed significant differences in the structure of the biosorbents used, which lead to the conclusion that sorption is associated with chemical changes on the surface of the biosorbent. The calculated values ​​of the parameters used in the Freundlich isotherm indicated the existence of high-energy sorption centers in the bisorbent of corn cob and corn silk hybrids maize, and that the adsorption was more pronounced at lower pH values. The corn cob-based  of the maize (Zea mays L.) biosorbent used has been shown to be a heterogeneous surface biosorbent with moderate sorption intensity to Ni and Cd ions, and good sorption intensity to Ni and Cd ions in corn silk-based biosorbent.