Adsorption of metal ions and dyes from aqueous solutions using lala clam (Paphia textile) shell

This study aimed to evaluate the effectiveness of lala clam shell as an adsorbent for the remediation of water contaminated by metal ions and dyes. Three main studies, namely adsorption, desorption and characterisation, have been conducted. In this study, Cd(II), Cu(II), Pb(II), Congo red (CR), Methylene blue (MB), Rhodamine B (RB) and Methyl orange (MO) were used as contaminants. A systematic evaluation for adsorption process involving several experimental parameters such as solution pH, adsorbent dosage and initial adsorbate concentration was performed. The applicability of lala clam shell to remove metal ions and dyes from aqueous solution was assessed in both single- and mixsystem. Hydrochloric acid (HCl) and ethylenediaminetetraacetic acid (EDTA) were used as desorption agents in desorption study. The characterisation study was carried out using Field Emission-Scanning Electron Microscope (FE-SEM), Energy Dispersive X-ray (EDX) Spectrometer and Fourier Transform Infrared (FTIR) Spectrometer. The surface morphology of lala clam shell changed significantly following interaction with metal ions and dyes. The adsorption equilibrium data of metal ions and dyes were correlated with both Langmuir and Freundlich isotherm models. The separation factor (RL) and Freundlich constant (n) values suggest that the adsorption process was favourable. At an initial metal ion concentration of 200 mg/L, the maximum adsorption capacity (Qmax) values of Cd(II), Cu(II) and Pb(II) were 66.66 mg/g, 64.94 mg/g and 100.00 mg/g, respectively. Meanwhile, at an initial dye concentration of 100 mg/L, 15.48 mg/g of CR, 1.50 mg/g of MO, 11.66 mg/g of MB and 0.31 mg/g of RB were adsorbed onto lala clam shell. The adsorption performance of lala clam shell was compared with mangrove stem derived activated carbon (MSAC), a commercial adsorbent for water treatment. In conclusion, the presence of carbonate functional group on lala clam shell enhanced its ability to adsorb metal ions and dyes. The implication of this study is lala clam shell offers an alternative low-cost adsorbent for water treatment particularly in developing countries such as Malaysia and Libya