Polycyclic aromatic hydrocarbons (PAHs) have been a problem in the environment for an extended period. They are mostly derived from petroleum, coal tar and oil spills that travel and are immobilized in wastewater/water sources. Their presence in the environment causes a hazard to humans due to their toxicity and carcinogenic properties. In the study, coal tar was analyzed using Gas Chromatography–Mass Spectrometry (GC–MS) and a concentration of 787.97 mg/L of naphthalene, followed by 632.15 mg/L of phenanthrene were found to be in the highest concentrations in the various water sources such as sewage, alkaline and acid mine drainage. A design column was used to investigate the leaching process and assessments were conducted on 300 mL of the various water sources mentioned, with 5 g of coal tar added and with monitoring for 4 weeks. The influence of the physiochemical properties of the receiving water sources, such as sewage, and acid and alkaline mine drainage, on the release of PAHs from the coal tar was assessed. The acidic media was proven to have the highest release of PAHs, with a total concentration of 7.1 mg/L of released PAHs, followed by 1.2 mg/L for the sewage, and lastly, 0.32 mg/L for the alkaline mine drainage at room temperature.

Heterogeneous photocatalysts have been widely used for the removal of various organic pollutants from wastewater. The main challenge so far resides in the sustainability of the process, with regard to the synthesis and the application under visible light. In this study the precipitated materials from the Moringa oleifera seed (MO), groundnut shells (GS) and apatite (A) agrowastes were functionalized with zinc oxide (ZnO) and silver (Ag) solution, to produce a novel bioheterophotocatalysts. Various analytical techniques such as scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and X-ray diffraction (XRD) were used for the characterization of the novel photocatalysts. It was proven that agrowastes can also enhance the photocatalytic activity of a ZnO-based photocatalyst as pure metals. The combination of MO/GS/A/ZnO/Ag in a 1:1:1 ratio resulted in a lower band gap of 1.59 eV, as compared to the band gap of 2.96 eV for ZnO/Ag. These photocatalysts' efficiency was also tested on the photodegradation of polycyclic aromatic hydrocarbon (PAHs) derived from coal leaching in various water sources such as acidic mine drainage, alkaline mine drainage and sewage wastewater. From MO/GS/A/ZnO/Ag, the removal efficiency was found to be 69.59%, 61.07% and 61.68%, compared to 52.62%, 37.96 and 44.30% using ZnO/Ag in acidic mine drainage, alkaline mine drainage and sewage wastewater for 60 min under solar irradiation.

There are many pollutants present in wastewater that require urgent remediation. Methylene blue (MB) has become the most undesirable pollutant. Various industries such as petroleum, pharmaceuticals, textiles and households have been responsible for releasing MB into the environment. Its toxicity and acute health implications for animals and humans have suggested several technological applications for its removal. Biological methods using plant‐based wastes have been identified to be the most effective material for removing MB and other dye pollutants. Previous research studies have employed biological adsorbents to eliminate MB and were reviewed. The purpose of the study was to determine the removal efficiency gap of MB using biological wastes. In this present review, various biological wastes and their functionalization were explored. The study proved that chemically modified bioadsorbents were favourable in removing MB. Its ability to produce secondary pollutants from chemical agents has made it undesirable. Several factors such as pH, dosage of catalyst, contact time and temperature have also been reviewed to influence biosorption. The best data representations to describe the biosorption of MB were the Langmuir and pseudo‐second‐order models.

Wastewater treatment has been widely focused on the undesirable pollutants derived from various activities such as coking, coal gasification, oil spills, and petroleum. These activities tend to release organic pollutants, however polycyclic aromatic hydrocarbons (PAHs) happen to be highlighted as the most carcinogenic pollutant that easily comes into contact with the environment and humans. It causes major challenges due to its lingering in the environment and chemical properties. Although various techniques such as ions exchange, advanced oxidation, and reverse osmosis have been conducted, some of them have been ignored due to their cost-effectiveness and ability to produce a by-product. Therefore, there is a need to develop and implement an effective technique that will alleviate the organic pollutants (PAHs) in various water sources. In this study, a self-made flat-bed photoreactor was introduced to degrade PAHs in various water sources such as acidic mine drainage, alkaline mine drainage, and sewage wastewater. A previous study was conducted, and only 7.074 mg/L, 0.3152 mg/L and 1.069 mg/L in 4 weeks and thereafter 19.255 mg/L, 1.615 mg/L and 1.813 mg/L in 8 weeks in acidic mine drainage, alkaline mined, drainage, and sewage wastewater leachate from a 2916.47 mg/L of PAHs in coal tar, was analysed. It was found that the flat-bed photoreactor was highly effective and able to obtain a removal efficiency of 64%, 55%, and 58%, respectively; without the flat-bed photoreactor, happened the removal efficiency was of 53%, 33%, and 39%, respectively, in 60 min in acidic mine drainage, alkaline mine drainage, and sewage wastewater. The photodegradation of PAHs was favoured in the acidic mine drainage, followed by sewage wastewater and alkaline mine drainage respective, showing time and solar irradiation dependence.

Asphaltene precipitation and deposition are well-known problems in the transportation and processing of oil recovery. The cause of asphaltene is triggered by various factors such as changes in pressure, temperature (T), and gas (carbon dioxide) flooding (CO₂). The study aimed to investigate the best economical method that can best enhance oil recovery (EOR). Two hybrid methods carbon dioxide flooding/ solvent (C₅) and carbon dioxide flooding/ solvent (C₅) /temperature were considered for the study. Firstly, the study was explored by singly utilizing pentane, hexane and heptane alkane solvents at different volumes to each of the three dead crude oils A, B and C. The study proves that the lower molecular weight and boiling point (C₅) managed to deasphaltene 24.0 g/mL from solvent/oil ratio 20:1/2; 100 mL into 2.5 g. This was due to the higher repulsive force between the solvent and the asphaltene. The study was further extended using the hybrid method and proven carbon dioxide/solvent (C₅)/temperature (90°) in precipitating higher asphaltene. The selection of pentane was based on its ability to meet the saturation point of the oil reservoir and EOR. The weaker London dispersion and the intermolecular forces between asphaltene and crude oil were the mechanisms responsible for the asphaltene precipitation.