Walnut Shells as Sustainable Low-Cost Adsorbents for the Removal of Cadmium and Nickel from Aqueous Solutions

The rapid development of industries has led to increased release of heavy metals into the environment. When released into the environment, metals have a tendency to linger eternally, build up in living tissues across the food chain, and endanger both the ecosystem and public health. Usually present in trace amounts in industrial wastewater, heavy metals are difficult to remove from water. In the current study, an adsorbent composed of walnut shells waste powder was manufactured and tested for the adsorption of heavy metals cadmium (Cd) and nickel (Ni) from synthetic aqueous solution. Several experimental conditions affecting the removal process were controlled, including pH, contact time, adsorbent dosage, temperature of solution, and initial concentration of Cd and Ni, to achieve optimal removal conditions. The adsorption technique was effectively implemented, attaining, under ideal circumstances, a removal efficiency of 95% for Cd and 99% for Ni. Additionally, the adsorption capacity (qe) of 14.25 mg/L for Cd and 14.85 mg/g for Ni. The optimum conditions for removing heavy metals (Cd and Ni) were: The initial metal concentrations are 30 mg/L, the bioadsorbent dosage is 2 g/L, the adsorbent particle size is between 0.3 and 0.075 mm, the agitation speed is 150 rpm, the contact period is 60 minutes, the pH is 5, and the solution temperature is 45°C. In summary, this study's suggested walnut shell material offers an economical, ecologically responsible, and alternative adsorbent for removing heavy metals from aqueous solutions by adsorption.