Application of Shrimp Waste Based Biomass for Removal of Heavy Metals (Cadmium(II), Copper(II), Nickel(II)) from Aqueous Phase

Abstract

Finding economical and environmentally friendly processes to remove heavy metals (HMs) from industries' influent is a research priority to move toward sustainability. Shrimp shell waste (SSW) could be converted to an efficient adsorbent for HM uptake from aqueous solutions. In this study, two methods - the conventional method and the deep eutectic solvents (DESs) method - are assessed for the removal of proteins and minerals from SSW and the extraction of chitin.

Chitin extracted by the conventional method (Ch-C ) and extracted by the DES method (Ch-DES) prepared to remove Cu(II), Cd(II) and Ni(II) from single-component aqueous solution in the first phase. The effect of experimental factors, including the pH, adsorbent dosage, initial concentration, and temperature on removal efficiency and adsorption uptake of Ch-C in a single-component system was evaluated to optimize the adsorption conditions. SEM, FT-IR and BET of the synthesized Ch-C confirmed the removal of protein and mineral components, increased surface area and pore volume, and uptake of HMs after adsorption. The isotherm study showed that Langmuir isotherm was the best fit to the experimental data of Cu(II), Cd(II) and Ni(II) adsorption on Ch-C and thermodynamic studies showed all the adsorption reactions were exothermic, physical and spontaneous. Then, Ch-C and Ch-DES were used for Cu(II), Cd(II) and Ni(II) adsorption from competitive aqueous media in the second phase. The Langmuir model showed that the maximum adsorption capacity of chitin in a multi-component system is for Cu(II), with maximum adsorption capacity of 42.20 mg/g for Ch-DES versus 32.88 mg/g for Ch-C, showing an improvement of approximately 28% for 𝑞_𝑚𝑎𝑥 under same experimental conditions. The 𝑞_𝑚𝑎𝑥 of Cd(II) and Ni(II) were 29.85 and 19.71 mg/g onto Ch-C, 38.25 and 23.48 mg/g onto Ch-DES. The pseudo-second-order best fitted all the experimental data and the thermodynamic study showed that all the adsorption reactions were exothermic, physical and spontaneous. While DESs were utilized as a green extraction medium for chitin, a comprehensive assessment should be conducted for the potential impacts to disposal or reuse, especially in large-scale applications.