Sustainable ligand-modified based composite material for the selective and effective cadmium(II) capturing from wastewater

The chemical ligand of N,N–bis(salicylidene)1,2–bis(2–aminophenylthio)ethane (BSBAE) was synthesized and then embedded indirectly on the mesoporous silica for the fabrication of optical composite materials (OCM) for toxic cadmium (Cd(II)) ion detection and removal from wastewater solutions. The variable parameters were measured including solution acidity, contact time, initial concentration, selectivity, and sensitivity, on the detection and removal of Cd(II) by the OCM. The solution pH played an important role in detection and removal but the present OCM worked well in the acidic pH region at 3.50. The data clarified that OCM formed distinguished color upon the addition of trace level of Cd(II) ions. The results also disclosed that the OCM was not affected by the existing diverse metal ions and the signal intensity was observed only toward the Cd(II) ion. The OCM was able to detect the low-level Cd(II) ion as the detection limit was 0.32 µg/L and the adsorption of the highest removal capacity was 179.65 mg/g. In addition, the diverse foreign ions were not reduced the Cd(II) ion adsorption significantly, and the OCM has approximately no adsorption capacity for other ions at this pH. The elution of Cd(II) ions from the saturated OCM was desorbed successfully with 0.25 M HCl. The regenerated OCM that remained maintained the high selectivity to Cd(II) ions and exhibited almost the same adsorption capacity as that of the original OCM. However, the adsorption efficiency slightly decreased after several cycles according to the experimental data observation. Therefore, the proposed OCM offered a cost-effective material and may be considered a viable alternative for effectively toxic Cd(II) ion detection and removal from wastewater as potential materials.