Economical synthesis of MOF from CHNS analyzer waste CuO and PET bottles for Congo red sequestration: a pathway towards dual mitigation

Abstract

The growing accumulation of non-biodegradable plastics worldwide is causing environmental havoc that needs to be effectively addressed immediately by providing a sustainable solution. In this regard, a Cu–PTA metal–organic framework (MOF) was synthesized from discarded PET bottles and waste copper (Cu) metal derived from CHNS analyzer oxidation tubes and utilized to remove Congo red (CR) from aqueous solutions. The synthesized Cu–PTA–MOF was analyzed using various characterizations to reveal their crystal lattices and compositional and morphological features. Subsequently, the efficacy of the synthesized MOF in the adsorption of Congo red dye (20 mg L⁻¹) was investigated. The optimized conditions were determined to be pH 7, an adsorbent dosage of 10 mg, and a contact time of 60 min, which resulted in a 95% removal efficiency and demonstrated the potential of the MOF for adsorption applications. Furthermore, the data were fitted to different isotherm models, which correlated with the Redlich–Peterson adsorption model, indicating monolayer and multilayer adsorption. The kinetic data also fitted well with the pseudo-second-order kinetic model, while thermodynamic analysis revealed that the adsorption of Congo red was exothermic, spontaneous and physisorption process. This study adds to the larger goal of promoting resilience and long-term viability in materials science and environmental engineering through waste valorization, as well as environmental remediation for adsorption applications.