Abstract

• The aim of the study was to prepare and characterize a chitosan based silica composite for the removal of Cr (VI) metal ions from aqueous solutions. In the current study, chitosan and silica were combined to prepare a chitosan-based silica composite with different mass ratios. Silica (SiO2) was obtained from the agricultural waste material of asparagus stalk ends. The prepared CS SiO2 composites were characterized by modern techniques like XRD, FT IR, SEM, UV-visible, and TG DTA analyses. The FT IR spectra showed the presence of new adsorption peaks (Si-O-Si bond), contributed by silica interaction with the hydroxyl group of chitosan. The study of morphology of the composite suggests that the SiO2 particles were within the range of 2–7 nm in diameter and were uniformly dispersed in the polymer matrix. The thermal properties of these composite materials, indicated that the thermal stability of the chitosan was enhanced. Under the experimental conditions, which include pH of the solution, adsorbent dose, initial concentration, contact time the sorption properties of the CS-SiO2 composite was observed for efficient removal of Cr (VI) ions from the aqueous solution. The adsorbent CS-SiO2 composite showed a maximum removal percent of Cr (VI) ions of 94. 65 %. These findings suggested that silica obtained from asparagus stalk ends could be utilized to enhance chitosan characteristics, decrease agricultural waste dumping, and decrease Cr (VI) metal ions polluting water.