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The presence of heavy metals in polluted water is known not only to cause severe harm to marine organisms, but also to terrestrial plants and animals including human beings. This research applied low-cost and environmentally benign adsorbent primed from waste orange peel (OP) for the removal of Cd(II) ions from aqueous solution via batch adsorption process. The surface properties of the orange peel powder were studied using scanning electron microscopy (SEM), X-ray spectroscopy (XRD) and Fourier transform infrared spectroscopy (FT-IR). Operational conditions like temperature, contact time, sorbent dosage, solution pH and initial adsorbate concentration were investigated. The utmost uptake of Cd(II) ion was obtained at a contact time of 120 min, initial metal concentration of 240 mg/L, adsorbent dosage of 0.04 g/L, temperature of 45 °C and solution pH of 5.5. Equilibrium results showed that the orange peel adsorbent has an adsorption capacity of 128.23 mg/g as obtained from the Langmuir isotherm. The adsorption kinetics data followed a pseudo-first-order kinetic model with correlation coefficient (R2) > 0.9 and low standard % error values. The adsorption process was found to be endothermic in nature with enthalpy of 0.0046 kJ mol−1 and entropy of-636.865 Jmol−1K−1. Results from the optimization study indicated that higher adsorbent dosage and lower Cd(II) ion concentration increased the percentage of Cd(II) ion removal. Thus, orange peel could be used in the removal of Cd(II) ion from aqueous solutions.

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Phthalate esters (PEs) are one of the environmentally active organic pollutants capable of causing endocrine disruption. The levels of PE congeners were determined in the influent and effluent from Covenant Oxidation Pond (COP) and Ikeja Wastewater Treatment Plant (IWWTP). Standard methods were adopted for determining the physical and chemical parameters of the water samples. The water samples for PE congener's determination were collected, acidified and stored at 4 °C prior to liquid-liquid extraction and analysis by gas chromatograph. The possible health risk associated with the usage of effluent-polluted river water was also investigated. The pH and temperature ranges were within the Federal Ministry of Environment (FME) 2001 guideline limits while the dissolved oxygen, biochemical oxygen demand and chemical oxygen demand were above the limits. The IWWTP performed better at removing PEs at 54% compared to 43.3% on average at COP. The health risk of individual PE congener showed no non-cancer effects (HQ) as the values varied from 5.01E-05 (DAP) to 1.52E-02 (DEHP) for adults and 1.17E-04 (DAP) to 3.76E-03 (DBP) for children at COP, while at IWWTP, it ranged from 8.06E-05 (DIBP) to 1.09E-02 (DEHP) for adults and 5.68E-04 (MMP) to 2.54E-02 (DEHP) for children. Notwithstanding, the usage of effluent-polluted river water by local communities downstream may result in carcinogenic effects due to the cumulative effects of the PE congeners as the values obtained for adults and children for the ingestion and dermal routes for the two waste process streams ranged from 4.67E-06 (IWWTP) to 6.22E-05 (IWWTP) and 2.18E-05 (IWWTP) to 7.18E-05 (COP), respectively.