Advanced Materials Research Vol. 1188

Abstract: This study explores the use of biochar derived from Ketapang (Terminalia catappa) leaf waste, prepared via a hydrothermal process and activated with KOH, as an adsorbent for removing mercury (Hg) from aqueous solutions. The study addresses the environmental challenge of heavy metal contamination using a low-cost, sustainable material. Activation increased the surface area of the biochar from 0.067 to 0.450 m²/g, enhancing its adsorption performance. The hydrothermal process was optimized at 220°C, where the biochar exhibited the highest Hg removal efficiency of 71.05% for a 50 ppm Hg(NO₃)₂ solution. The adsorption behavior was best described by the Langmuir isotherm model, indicating monolayer adsorption on a homogeneous surface. The adsorption mechanism likely involves physical and chemisorption interactions, supported by changes in surface morphology, functional groups, and elemental composition. This study demonstrates the promising application of Ketapang leaf biochar as an eco-friendly adsorbent for mercury removal, with implications for water treatment technologies.

Abstract: Chitosan and clay materials of 50:50 ratio, produced and characterized from periwinkle shells and clay soil, was applied to capture CO₂ from gas mixture at elevated temperatures (50^OC to 250^OC) in a column bed, packed with the particles of dimension length 1.5 (m), and inner diameter 0.02 (m). The composition of gas mixture are 0.003, 0.002, 0.05, 0.15, 0.02, and 0.76 for CH_4, C₂H_6, H_2, CO_2, H₂O vapour, and N_2, respectively at condition of pressure 49 (kPa), temperature 250^OC, and flow rate 75 (L/min) from exhaust column into the column bed for adsorption process. The kinetic and isotherm models are adopted and simulations performed from the experimental data to determine suitable adsorption parameters for the process. Also, Aspen plus and statistical optimization tool to simulate the experimental data are utilized to determine the optimal yield and conditions of factors. The coefficient of determination of 0.992 showed that the quadratic model is best suitable for the combination of parameters and fitted well, while the optimization result gave significant difference among the bed height, temperature and time and their interactions. The result revealed that the adsorption process best followed Elovich kinetic and fitted well in the Freundlich multilayer adsorption isotherm with parameters 0.0187 (mg/g.hr), 175.932, and 1.5 for the kinetic constant, adsorption constant, and intensity respectively. The root means square errors and deviation values gave negligible values of 0.166; 0.045, and 0.0345; 0.0094 for the design/simulation; optimization models applied, when compared to the experimental data. The regression results of the factors analysis showed that the model R² of 0.995 is more reliable and fitted well than the modified R² of 0.985 and the estimated R² of 0.965. The central composite design for the optimization of the process gave maximum yield of 0.9411 at suitable combine time and temperature factors effect. Aspen plus simulation result gave yield of 0.9831 CO₂ removed from optimal conditions of time, temperature, and bed height of 2.8 (hrs), 155.6°C, and 3.44 (cm) respectively. It was noticed that N₂, CH₄, C₂H₆, and water vapour were removed from the gas mixture of yields 0.9972, 0.9832, 0.9831, and 0.9947 respectively.