The reduction of chemical oxygen demand (COD) from palm oil mill effluent (POME) is very significant to ensure aquatic protection and the environment. Continuous adsorption of COD in a fixed bed column can be an effective treatment process for its reduction prior to discharge. Adsorption capacity of bone derived biocomposite synthesized from fresh cow bones, zeolite, and coconut shells for the reduction in the organic pollutant parameter was investigated in this study in a fixed bed column. The effect of influent flow rate (1.4, 2.0, and 2.6 mL/min) was determined at an influent pH 7. The optimum bed capacity on the fabricated composite of surface area of 251.9669 m²/g was obtained at 1.4 mL/min at breakthrough time of 5.15 h influent POME concentration. The experimental data were fitted to Thomas, Adams–Bohart, and Yoon–Nelson models fixed bed adsorption models. It was revealed that the results fitted well to the Adams Bohart model with a correlation coefficient of R² > 0.96 at different influent concentration. Adsorption rate constant was observed to increase at lower flow rate influent concentration, resulting in longer empty bed contact time (EBCT) for the mass transfer zone of the column to reach the outlet of the effluent concentration. In general, the overall kinetics of adsorption indicated that the reduction in COD from POME using a bone-biocomposite was effective at the initial stage of adsorption. The pore diffusion model better described the breakthrough characteristics for COD reduction with high correlation coefficient. Shorter breakthrough time compared to EBCT before regeneration indicated that the bone composite was suitable and effective for the reduction in COD from POME using fixed bed column adsorption.

This study aimed to develop a novel composite adsorbent combining peat (PS), limestone (LS), zeolite (ZEO), and activated carbon (AC), with ordinary Portland cement (OPC) as a binder (40% by weight), for the simultaneous removal of ammoniacal nitrogen (NH₃-N) and chemical oxygen demand (COD) from stabilized landfill leachate. The composite was characterized using X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, and pH at zero-point charge (pHzpc). The material exhibited high SiO₂ and CaO content, functional groups (e.g., Si–O-Si, N–H, O–H, C–O, C–N, and O–C.), a rough and heterogeneous surface morphology, a surface area of 105.96 m²/g, and a pHzpc of 11.25. Batch experiments determined optimal adsorption conditions: 200 rpm shaking speed, 120-min contact time, pH 7, particle size of 2.36–3.35 mm, and dosage of 57 g/L. The Langmuir isotherm model provided the best fit for NH₃-N and COD adsorption with adsorption capacities of 26.18 mg/g and 47.39 mg/g, respectively (R² = 0.9941 and 0.9814). Kinetic studies indicated pseudo-second-order kinetics, suggesting chemisorption as the rate-limiting process. These findings demonstrate the composite (PS, LS, ZEO, and AC) potential as an efficient and sustainable adsorbent for treating stabilized landfill leachate. Further studies should focus on evaluating the performance of composite adsorbents for the removal of NH₃-N, COD, or other pollutants from mining industry, domestic, or combined effluents, as well as their potential application in air pollution control.

The performance of carbon mineral-combined adsorbents in a batch and fixed column study was examined for removing chemical oxygen demand (COD) and ammoniacal nitrogen (NH₃-N), which typically found in landfill leachate. The batch experiment was carried out using various factors including adsorbent dosages and retention time, while column performance was evaluated by optimizing the influent flow rate. The surface of the composite adsorbent was examined using X-ray fluorescence (XRF), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) to determine any changes before and after column operations. The XRF analysis of the composite adsorbent reveals a high concentration of calcium oxide and silica oxide as the primary compounds. The main functional groups in the composite adsorbent included O–H, N–H, O–C, C–N, C–O, and Si–O–Si. The SEM analysis revealed that the composite adsorbent contains heterogeneous pores and a rough surface. The reduction rates achieved were 86% for COD, with an optimum adsorption capacity of 31.3 mgg⁻¹, and 80% for NH₃-N, with an optimum adsorption capacity of 29.8 mgg⁻¹. The breakthrough capacities for COD and NH₃-N adsorption were 6.55 and 4.24 mgg⁻¹, respectively. However, optimal empty-bed contact times (EBCTs) in minutes were 480. The performance efficiency of the column for COD and NH₃-N was 0.9978% and 0.9913%, by utilizing fresh composite adsorbent, and these number figures increased to (≥ 0.9998%) respectively after the regeneration process. The Adams–Bohart constant for COD from 5.30 × 10^–6 to 4.92 × 10^–6 mL/min-mg and NH₃-N from 2.90 × 10^–5 to 4.52 × 10^–5 mL/min-mg respectively was found to increase with increasing flow rates from 1.5 to 3.0 mLmin⁻¹. Therefore, COD and NH₃-N adsorption on composite adsorbent at flow rates of 1.5 mLmin⁻¹ was considered appropriate from the context of this study. In summary, this research has successfully shown that the use of composites as an adsorbent is a viable and suitable for the removal of COD and NH₃-N from leachate, indicating their potential for use in real-world industrial wastewater treatment could further enhance their practical applications.