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This paper demonstrates for the first time the feasibility of utilizing waste mussel shells for the synthesis of hydroxyapatite, Ca 10 (PO) 6 (OH) 2 (denoted as HAP) to be used as a greener, renewable photocatalyst for recalcitrant wastewater remediation. HAP was synthesised from Perna Canaliculus (green-lipped mussel) shells using a novel pyrolysis-wet slurry precipitation process. The physicochemical properties of the HAP were characterized using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The HAP produced was of comparable quality to commercial (Sulzer Metco) HAP. The synthesized HAP had good photocatalytic activity, whereby methylene blue (a model textile wastewater compound) and its azo dye breakdown products were degraded with an initial rate of 2.5 x10-8 mol L-1 min-1. The overall azo dye degradation was nearly 54% within 6 hours and 62% within 24 hours in an oxygen saturated feed in a batch reactor using a HAP concentration of 2.0 g/L, methylene blue concentration of 5 mg/L, UV irradiation wavelength of 254 nm and a stirring speed of 300 rpm. The kinetics were well described by three first order reactions in series, reflecting the reaction pathway from methylene blue to azo dye intermediates, then to smaller more highly oxidised intermediates and finally degradation of the recalcitrants. The final two steps of the reaction had significantly slower rates than the initial step (rates constants of 6.2 x 10-3 min-1 , 1.2x10-3 min-1 and approximately (due to limited data points) 1.6x10-4 min-1 for the first, second and third step respectively), which tie in with this mechanism, however it could also indicate that the reaction is either product inhibited and/or affected by catalyst deactivation. FTIR analysis of the post-reaction HAP revealed surface PO 4 3group loss. Since there is good photocatalytic activity with oxygen in limited and excess supply during the photoreaction, this indicates the possibility of lattice oxygen participation in the photocatalytic reaction, which 3 needs to be characterised more fully. However, overall, these results indicate that the HAP derived from the mussel shells is a promising greener, renewable photocatalyst for the photocatalytic degradation of wastewater components.

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Photocatalysis has merged to be one of the most promising technology in wastewater remediation. However, the application of photocatalysis in treating palm oil mill effluent (POME) is still limited. Many researches were conducted to explore simple and cost-effective alternatives to replace TiO2 for various industrial purposes. Therefore, the aim of this study is to synthesize and characterize lanthanum doped calcium oxide (La/CaO) as photocatalyst as well as to evaluate the performance of these photocatalysts in the degradation of POME. The photocatalyst used in this study was converted from cockle shells to transform into calcium oxide (CaO) through calcination process. The CaO produced was doped with 1 wt%, 3 wt%, and 5 wt% of lanthanum (La) using wet impregnation method to enhance its photocatalytic activity. The photocatalysts were characterised using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Energy-Dispersion X-ray (EDX), and Inductively Coupled Plasma Mass Spectrometry (ICPMS). Then, this photocatalyst was performed on POME under UVC in a batch system by using different La/CaO at optimum catalyst dosage of 3.0 g/L. Through this research, it was found that the POME degradation through photocatalytic reaction was increased with the incorporation of La where 3 wt% La/CaO showed the highest POME degradation compared to others. This is due to the larger BET surface area that provides more active sites resulted from the incorporation of La. The findings of this study imply that the contaminants in POME can be reduced by utilizing CaO derived from cockle shells. , respectively [1]. Freely discharged of POME can bring severe impacts to the environment and increase the likelihood of affecting the aquatic life and decreasing the water quality because it contains high level of pollutants such as suspended solid, residual oil and grease, chemical oxygen demand (COD), and biochemical oxygen demand (BOD). At presence, numerous conventional methods have been used in treating POME such as anaerobic digestion [2][3][4][5], membrane technology [6][7][8], and adsorp-