Sorption of Selected Metals from Cement Factory Wastewater using Alkali Activated Carbons Derived from PET (Polyethylene terephthalate)

Background and Objective: Cocoa husk and Polyethylene terephthalate (PET) are solid wastes that need to be sustainably managed. This study evaluated the effect and efficiency of Cocoa Ash alkali-polyethylene terephthalate (CAPET) and KOH PET activated carbons (ACs) for removal of selected metals (Ca, Cr, Zn, Mn, Cu and Fe) from cement factory wastewater. Materials and Methods: Scanning Electron Microscope coupled with Energy Dispersive X-ray Spectrophotometer (SEM/EDX) and Fourier Transform Infrared Spectrometer (FTIR) were used to characterize the ACs. Using ICP-OES, the initial and final concentrations of metals present in wastewater were determined. Langmuir and Freundlich sorption isotherm models were applied to determine metals’ interface with alkali-PET adsorbents. Results: The carbon yield of alkali-PET (CAP and KOH PET) ACs were 81.4 and 91.1%, respectively. The EDX analysis of the ACs also resulted in carbon having the highest composition. The results of the adsorption using CAPAC and KPAC as adsorbents revealed that concentrations of some metals (Cr, Zn, Mn, Cu and Fe) were below detection level (0.00 mg L‾¹) in both upstream and downstream wastewater samples, with the exception of Calcium (Ca). This implies 100% adsorption efficiency for metals (Cr, Zn, Mn, Cu and Fe) and 95% for Ca. The Freundlich adsorption isotherm fits the experimental data better than the Langmuir adsorption isotherm. Conclusion: The study indicated that rather than polluting the environment, PET and cocoa husk might be processed to act as low-cost, non-hazardous adsorbents for eliminating metal pollutants from wastewater.