Alginate-Immobilized Arachis hypogaea Hull: Characterization, Kinetics, and Sustainable Biosorption Removal of Some Toxic Metals from Municipal Wastewater

Sustainable development is seriously hampered by environmental contamination. Heavy metals are perhaps the most significant of these silent pollutants because of the poisoning they inflict on different ecosystems, particularly water systems, as well as the direct threat they pose to the safety of such systems and the ensuing health issues that affect people and other living things. The goal of the current work is to ascertain how effective peanut (Arachis hypogaea) hulls are as easily accessible and reasonably priced adsorbent materials for the ion adsorption of various heavy metals, including lead, copper, zinc, and cadmium. A series of variables, such as pH, temperature, retention time, shape, quantity of adsorbent and particle size, were investigated to reach the optimal conditions for the biosorption process, which were achieved at pH 6 (close to pH-zero charge), a temperature of 40 °C, a retention time of 60 min, an adsorbent dose of 5 g/L, and a particle diameter of 0.1 mm. Experiments showed that lead had the highest treatment rate, approximately 95%, followed by zinc, copper, and cadmium. The results were confirmed and validated using SEM analysis to identify the morphology of the hulls before and after treatment, FTIR spectroscopy to investigate the functional groups responsible for binding to the metal ions, and further supported by kinetic isotherms of the adsorption behavior, which matched the Langmuir and Freundlich models. Nevertheless, the results of the batch experiment were employed by designing a laboratory treatment unit for municipal wastewater containing beads of alginate-immobilized Arachis hypogaea hulls. The designed laboratory unit was effective in treating unacceptable levels of heavy metals in some municipal wastewater from the local drainages of Ramadi City, Iraq. Overall, the study’s findings suggested that peanut hulls could be used to mitigate toxic metal pollution in an eco-friendly manner that guarantees the accomplishment of the Sustainable Development Goals pertaining to future generations’ right to the safe use of water resources.