Hairul Nazirah Abdul Halim

Emulsified oil in wastewater generated by food industries has been a significant environmental issue worldwide. Therefore, rubber seed kernels (RSKs) have been utilized as a precursor in synthesizing activated carbon (AC) for removing oil from oil‐water emulsion. Rubber seed kernel‐based activated carbon (RSK‐AC) was produced with different impregnation ratios of H ₃ PO ₄ to RSKs (1:1, 1.5:1, and 2:1 wt./wt.) and carbonized at 500°C for 1.5 h to enhance its surface area and porosity. Batch adsorption experiments using 0.4 g RSK‐AC prepared at the impregnation ratio of 2:1 wt./wt. and contacted with a 200 ppm oil‐water emulsion at pH 7 and 35°C achieved the highest oil adsorption capacity of 67.17 ± 3.83 mg/g. The chemical activation and carbonization of RSKs have significantly improved the surface area of the resultant RSK‐AC to 137.233 m ² /g, with increased carbon content and the presence of aromatic moieties. The Freundlich isotherm model provided well‐fitted data, while the kinetics studies could be described by the pseudo‐first‐order kinetics model. The thermodynamic analysis revealed that the adsorption of emulsified oil onto RSK‐AC was spontaneous and exothermic. Based on these results, RSK‐AC could be used as a sustainable adsorbent for emulsified oil adsorption.

Activated carbons (AC) are widely used as adsorbents for treating oily wastewater. An effective, cheap and environmental-friendly method for oil adsorption by using AC derived from jackfruit seeds (JS) was developed in this study. The JS were chemically activated with different concentrations (10 wt.% and 15 wt.%) of chemical activating agents (H3PO4 and ZnCl2) to produce activated carbon. The optimum conditions for developing AC from JS with the highest oil adsorption capacity was found using 15 wt.% ZnCl2, and carbonised at 500°C resulting in maximum adsorption capacity of 0.8621 g/g. Raw JS and jackfruit seed-derived activated carbon (JSAC) were characterized by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy analysis. The influence of process parameters such as contact times (0 – 240 minutes), adsorbent dosages (0.5 – 2.5 g) and adsorption temperatures (25 – 65 °C) for oil adsorption were investigated. The results showed that the optimum parameters for maximum adsorption capacity were as follows; 120 minutes of contact time, adsorbent dosage of 1.5 g and at 35 °C. At this condition, the highest oil adsorption capacity was achieved at 1.5674 g/g. The adsorption kinetic studies depicted that the oil adsorption mechanism was represented by pseudo-second-order kinetic model which implies that the adsorption is a chemisorption process. Jackfruit seeds had been proven to have the capability as an effective adsorbent for oil adsorption.

The operational and economic constraints suffered by amine solvents for CO₂ removal have motivated the research on an alternative solvent with better performance and cost-effectiveness. Amino acid salt (AAS) has been identified as an interesting green solvent, an alternative to commercial amine solvents. The present work evaluated the physicochemical and CO₂-solubility properties of potassium L-cysteine (K-CYS), a naturally occurring amino-acid-based solvent for CO₂ removal from natural gas. Its physicochemical properties, including density, viscosity, and refractive index, were measured at different temperatures ranging between 298.15 and 333.15 K and a concentration range of 5 to 30 wt.%. Based on the experiment, all properties were found to decrease with increasing temperature and increase with increasing concentration. The experiments also demonstrated a significant reduction of CO₂ loading from 2.4190 to 1.1802 mol of CO₂/mol of K-CYS with increasing solvent concentration from 10 to 30 wt% at 313.15 K and 20 bar (g).

The increase in food industrial and domestic activities have led to massive generations of oily wastewater with high proportions of fat, oil, and grease (FOG). The growing awareness of the detrimental effects of oil pollutants on the aquatic population and the economy, has made the minimal discharge of FOG into the environment a compulsory mitigative measure. In this work, spent coffee grounds (SCGs) were exploited as an oil adsorbent to minimize the amount of SCGs that are primarily discarded as waste. SCGs were pre-treated with alkali to enhance their performance for adsorbing oil. Batch adsorption tests that consisted of contact time, adsorbent dosage, and temperature for oil adsorption, were carried out to analyse the performance of the alkali-treated SCGs. Based on the results, the maximum oil adsorption capacity was obtained after 150 min of contact time between 0.5g of alkali-treated SCG adsorbents and oil, at 25 °C. These alkali-treated SCGs have also shown the potential for converting wastes into efficient green oil adsorbents.

CO₂ removal is important for industrial flue gas treatment, biogas enhancement, and natural gas (NG) processing applications. Chemical absorption using an amine-based solvent is a proven technology for CO₂ removal from various gases. In recent years, various promising amine solvents have been investigated, either as single or blended solutions, to enhance the CO₂ absorption process at low and high CO₂ partial pressure conditions. Low CO₂ partial pressures (1 – 47 kPa) have been utilized in numerous research works focusing on flue gas treatment and biogas enhancement applications. On the other hand, high CO₂ partial pressures were instead applied in NG processing ranging between 750 and 1600 kPa. To provide more insight into the current trends, existing research on CO₂ absorption in amine-based solvents is presented in this review focusing on absorption performance in a packed column at low and high CO₂ partial pressures. Reports on the effect of different parameters, namely CO₂ partial pressure, gas, and liquid flow rates, amine concentrations, and liquid temperature, on the removal of CO₂ in the packed column are included. Based on the review, the future direction is further highlighted in this area.