Oil-contaminated or oily wastewater (OW) is generated from various industrial and domestic premises. It consists of fats, oils, and greases and may contain petroleum fractions such as diesel oil, gasoline, and kerosene. It is regarded as one of the most hazardous wastewaters, causing serious environmental and health threats to ecosystems and human beings. The global increase in the discharge of OW coupled with stringent regulations for effluent discharge and incessant drive for the reuse of treated wastewater necessitate the need for the treatment of the OW. Conventional approaches employed in the past are inept for OW treatment due to low separation efficiency, high operational cost, creating secondary pollution, and long treatment hours. Comparatively, the adsorption process is considered a better alternative because of its simple design and can involve low investment in terms of both initial cost and land required. Thus, the adsorption process is widely applied as a promising alternative to existing treatment methods for OW. The adsorption process is an effective technique for OW treatment. Super adsorbents with ultrahigh adsorption capabilities are highly desired for efficient OW treatment in a new revolution of adsorption technology to meet present and future needs. This review provides insights into advanced and emerging state-of-the-art technologies of the adsorption process as a safe and efficient treatment of OW. Strength, weakness, opportunities and threats (SWOT) analysis was conducted to identify and analyze internal strengths and weaknesses and external opportunities and threats that shape the current and future operation of the adsorption process for the treatment of oily wastewater for developing strategic goals. Super adsorbents with ultrahigh adsorption capability such as P-GSC and P-PKS discussed are highly desired. The extraordinary properties of P-GSC and P-PKS can provide leap-forward opportunities to revolutionize traditional adsorption technology. However, scale-bridging and optimization study of these innovated super adsorbents is required for the real application. It shows a bright future of P-GSC and P-PKS towards OW treatment.

Oily wastewater (OW) is detrimental towards the environment and human health. The complex composition of OW needs an advanced treatment, such as membrane technology. Membrane distillation (MD) gives the highest rejection percentage of pollutants in wastewater, as the membrane only allows the vapor to pass its microporous membrane. However, the commercial membranes on the market are less efficient in treating OW, as they are prone to fouling. Thus, the best membrane must be identified to treat OW effectively. This study tested and compared the separation performance of different membranes, comparing the pressure-driven performance between the membrane filtration and MD. In this study, several ultrafiltration (UF) and nanofiltration (NF) membranes (NFS, NFX, XT, MT, GC and FILMTEC) were tested for their performance in treating OW (100 ppm). The XT and MT membranes (UF membrane) with contact angles of 70.4 ± 0.2° and 69.6 ± 0.26°, respectively, showed the best performance with high flux and oil removal rate. The two membranes were then tested for long-term performance for two hours with 5000 ppm oil concentration using membrane pressure-filtration and MD. The XT membrane displayed a better oil removal percentage of >99%. MD demonstrated a better removal percentage; the flux reduction was high, with average flux reduction of 82% compared to the membrane pressure-filtration method, which experienced a lower flux reduction of 25%. The hydrophilic MT and XT membranes have the tendency to overcome fouling in both methods. However, for the MD method, wetting occurred due to the feed penetrating the membrane pores, causing flux reduction. Therefore, it is important to identify the performance and characteristics of the prepared membrane, including the best membrane treatment method. To ensure that the MD membrane has good anti-fouling and anti-wetting properties, a simple and reliable membrane surface modification technique is required to be explored. The modified dual layer membrane with hydrophobic/hydrophilic properties is expected to produce effective separation in MD for future study.

This work is aimed to develop polyethersulfone (PES) nanofiltration (NF) membrane with layer-by-layer (LBL) polyelectrolytes of chitosan (CHI) and poly(acrylic acid) (PAA) for xylitol purification from fermentation broth. Different number of bilayers and type of terminating layer were manipulated for producing more hydrophilicity, negatively charged with improved performance compared to pristine PES membrane. Successful deposition of polyelectrolyte layers onto PES membrane was able to be proven using various tests such as contact angle, Zetasizer and FT-IR. The results obtained have proven that LBL can develop PES membrane with higher resistance to fouling. From Zeta potential analysis, the value of pristine PES membrane's negativity confirmed the theory of negatively charged substrate for LDL. The negative value of PES membrane increased from -16.5 mV to -32.7 mV after being modified to PES (CHI/PAA)6. From FT-IR spectra, the formation of CHI/PAA complexes on the membrane's surface is confirmed through the presence of stretching peaks of -COOH, -NH3+ and -NH2+ groups The pure water flux reduces from 47.40 ±6.30 L⁄m2.h to 7.40 ±1.64 L⁄m2.h after being modified to PES (CHI/PAA)2. The rejection performance of xylitol for PES (CHI/PAA)2 is higher (84.95%) than pure PES membrane (66.17%), while (CHI/PAA)4 offered the lowest selectivity towards xylitol than arabinose and thus able to obtain higher purity of xylitol as retentate. LBL surface modification using CHI/PAA can develop PES membrane with higher hydrophilicity, negatively charge, and is able to give better xylitol rejection compared to pure PES.