Application of Orange Peel Waste as Adsorbent for Methylene Blue and Cd²⁺ Simultaneous Remediation

Pollution by dyes and heavy metals is one of the main concerns at the environmental level due to their toxicity and inefficient elimination by traditional water treatment. Orange peel (OP) without any treatment was applied to effectively eliminate methylene blue (MB) and cadmium ions (Cd²⁺) in mono- and multicomponent systems. Although the single adsorption processes for MB and Cd²⁺ have been investigated, the effects and mechanisms of interactions among multicomponent systems are still unclear. Batch experiments showed that in monocomponent systems, the maximum adsorption capacities were 0.7824 mmol g^-1 for MB and 0.2884 mmol g^-1 for Cd²⁺, while in multicomponent systems (Cd²⁺ and MB), both contaminants competed for the adsorption sites on OP. Particularly, a synergic effect was observed since the adsorption capacity of Cd²⁺ increased compared to the monocomponent system. Results of desorption and adsorbent reuse confirmed that the adsorbent presents good regeneration performance. The low cost of this material and its capacity for the individual or simultaneous removal of Cd²⁺ and MB in aqueous solutions makes it a potential adsorbent for polluted water treatment processes.