Increasing water pollution and decreasing energy reserves have emerged as growing concerns for the environment. These pollution are due to the dangerous effects of numerous pollutants on humans and aquatic organisms, such as hydrocarbons, biphenyls, pesticides, dyes, pharmaceuticals, and metal ions. On the other hand, the need for a clean environment, finding alternatives to fossil and renewable fuels is very important. Hydrogen (H₂) is regarded as a viable and promising substitute for fossil fuels, and a range of methodologies have been devised to generate this particular source of energy. Metal-organic frameworks (MOFs) are a new generation of nanoporous coordination polymers whose crystal structure is composed of the juxtaposition of organic and inorganic constituent units. Due to their flexible nature, regular structure, and high surface area, these materials have attracted much attention for removing various pollutants from water and wastewater, and water splitting. MOFs Z-scheme heterojunctions have been identified as an economical and eco-friendly method for eliminating pollutants from wastewater systems, and producing H₂. Their low-cost synthesis and unique properties increase their application in various energy and environment fields. The heterojunctions possess diverse properties, such as exceptional surface area, making them ideal for degradation and separation. The development and formulation of Z-scheme heterojunctions photocatalytic systems using MOFs, which possess stable and potent redox capability, have emerged as a successful approach for addressing environmental pollution and energy shortages in recent times. Through the utilization of the benefits offered by MOFs Z-scheme heterojunctions photocatalysts, such as efficient separation and migration of charge carriers, extensive spectrum of light absorption, among other advantages, notable enhancements can be attained. This review encompasses the synthesis techniques, structure, and properties of MOFs Z-scheme heterojunctions, and their extensive use in treating various wastewaters, including dyes, pharmaceuticals, and heavy metals, and water splitting. Also, it provides an overview of the mechanisms, pathways, and various theoretical and practical aspects for MOFs Z-scheme heterojunctions. Finally, it thoroughly assesses existing challenges and suggests further research on the promising applications of MOFs Z-scheme in industrial-scale wastewater treatment.

The study aims to treat artificial wastewater contaminated with copper (II) ions by reverse osmosis using (SEPA CF042 Membrane Test Skid-TFC BW30XFR). Several concentrations of feedstock were prepared. Different operating pressure, temperature, and flow rate were applied. The effect of these operating conditions on both the amount of Cu (II) removal and the permeate flux was monitored. The results of the study revealed that both the permeate flux and Cu (II) removal amount were directly proportional to the operating pressure and feed temperature but inversely proportional to the feed concentration. In contrast, the feed flow rate showed a negligible effect on the permeate flux and Cu (II) removal amount. The temperature correction factor (TCF) of the membrane was calculated and was found to be directly proportional to the feed temperature but inversely proportional to the applied pressure. It was seen that the concentration and flow rate of that feed did not affect the temperature correction factor. Mathematical models have been developed based on these experimental data for both permeate flux and the Cu (II) removal. It was noted that the permeate flux model matched the experimental data, while the Cu (II) removal model did not show a perfect match. In addition to the above, the research highlights for subsequent studies the possibility of a deep link between experimental work and mathematical models.

In this work, the capture of carbon dioxide using a dense hollow fiber membrane was studied experimentally and theoretically. The factors affecting the flux and recovery of carbon dioxide were studied using a lab-scale system. Experiments were conducted using a mixture of methane and carbon dioxide to simulate natural gas. The effect of changing the CO₂ concentration from 2 to 10 mol%, the feed pressure from 2.5 to 7.5 bar, and the feed temperature from 20 to 40 °C, was investigated. Depending on the solution diffusion mechanism, coupled with the Dual sorption model, a comprehensive model was implemented to predict the CO₂ flux through the membrane, based on resistance in the series model. Subsequently, a 2D axisymmetric model of a multilayer HFM was proposed to simulate the axial and radial diffusion of carbon dioxide in a membrane. In the three domains of fiber, the CFD technique was used to solve the equations for the transfer of momentum and mass transfer by using the COMSOL 5.6. Modeling results were validated with 27 experiments, and there was a good agreement between the simulation results and the experimental data. The experimental results show the effect of operational factors, such as the fact that temperature was directly on both gas diffusivity and mass transfer coefficient. Meanwhile, the effect of pressure was exactly the opposite, and the concentration of CO₂ had almost no effect on both the diffusivity and the mass transfer coefficient. In addition, the CO₂ recovery changed from 9% at a pressure equal to 2.5 bar, temperature equal to 20 °C, and a concentration of CO₂ equal to 2 mol%, to 30.3% at a pressure equal to 7.5 bar, temperature equal to 30 °C, and concentration of CO₂ equal 10 mol%; these conditions are the optimal operating point. The results also manifested that the operational factors that directly affect the flux are pressure and CO₂ concentration, while there was no clear effect of temperature. This modeling offers valuable data about the feasibility studies and economic evaluation of a gas separation unit operation as a helpful unit in the industry.

The reverse osmosis performance in removing nickel ions from artificial wastewater was experimentally and mathematically assessed. The impact of temperature, pressure, feed concentration, and feed flow rate on the permeate flux and Ni (II) rejection % were studied. Experiments were conducted using a SEPA CF042 Membrane Test Skid—TFC BW30XFR with applied pressures of 10, 20, 30, and 40 bar and feed concentrations of 25, 50, 100, and 150 ppm with varying operating temperatures of 25, 35, and 45 °C, while the feed flow rate was changed between 2, 3.2, and 4.4 L/min. The permeate flux and the Ni (II) removal % were directly proportional to the feed temperature and operating pressure, but inversely proportional to the feed concentration, where the permeate flux increased by 49% when the temperature was raised from 25 to 45 °C, while the Ni (II) removal % slightly increased by 4%. In addition, the permeate flux increased by 188% and the Ni (II) removal % increased to 95.19% when the pressure was raised from 10 to 40 bar. The feed flow rate, on the other hand, had a negligible influence on the permeate flux and Ni (II) removal %. The temperature correction factor (TCF) was determined to be directly proportional to the feed temperature, but inversely proportional to the operating pressure; nevertheless, the TCF was unaffected either by the feed flow rate or the feed concentration. Based on the experimental data, mathematical models were generated for both the permeate flux and nickel removal %. The results showed that both models matched the experimental data well.

Fish-process wastewater industries are a significant source of environmental pollutions and biohazard to humans and other living organisms due to suspended organics, phosphorus, and nitrate that causes environmental damage. In this study, the treatment of two types of fish wastewater was examined by applying chemical and physical methods. The chemical treatments using positive polyelectrolyte with a concentration of 25 ppm reduced the turbidity of fish wastewater by 50%; conductivity was reduced by 50% and pH was reduced from 8 to 7.2. Meanwhile, using negative polyelectrolyte and mixed polymers reduced the turbidity of fish wastewater by 30%. For applying natural material as a physical adsorbent, several natural materials were examined: ocimum leaves, Boswellia sacra leaves, Al-Shakher leaves, tephrosia leaves, neem leaves, mentha leaves, jand peel, neem wood, ocimum fruit, olive fruit peel, and palm anguish for the treatment of the fish wastewater. The initial tests indicated that the best material was palm anguish. FTIR, SEM, and EDS were used for the characterization of palm anguish. The selected material was treated with 1 M of NaOH solution. Different bed heights (10, 20, and 30 cm) of Palm anguish were applied. The results showed 80% and 85% reduction in the turbidity in both types of fish wastewater, especially with a bed height of 30 cm of the fish wastewater treated with NaOH, respectively. Notably, this study distinguishes itself by utilizing polyacrylamide flocculants of varying densities and by employing palm anguish as a natural adsorbent, which can sufficiently improve the treatment of fish-processing wastewater.

Removal of organic pollutants and metal ions from produced water by adsorption, using prepared activated carbon (AC) from sewage sludge, with chemical activations using NaOH, KOH and ZnCl₂ separately and pyrolysis at different temperatures (500, 600 and 700 °C). Pure sludge and prepared ACs were analyzed using FTIR and XRD. The results showed 18% crystallinity compared to that of commercial AC, which has 44% crystallinity. The results of FTIR demonstrate that the properties of the post-treated affect the final products depending on the method used and that it contains similar functional groups to those present in the commercial AC, but at a higher peak intensity. Adsorption treatments were carried out at 25, 35 and 45 °C solution temperatures. The results showed that the removal of pollutants from produced water using prepared AC with all types of chemical activations reached 99.5%, such as commercial AC with 0.06 g dosage of adsorbent at pyrolysis temperatures of 500 and 600 °C and a solution temperature of 25 °C. The obtained results refer to the mechanism of exothermic reaction and physical adsorption. It was observed that despite the lower dosage of adsorbent of 0.01 g, a sufficient treatment of pollutants was achieved. This reveals the effectiveness of using sewage sludge as a cheap adsorbent. Also, using pure sewage sludge, the adsorption data showed a 95.2% removal of the pollutants. This result indicated that pure sludge has an efficient adsorption capacity and can be utilized as a cheap and environmentally friendly material. For the removal of manganese and cadmium metal ions from the produced water, the resultant data showed that more than 90% of manganese was adsorbed and more than 97% of cadmium was adsorbed, especially when using pure sewage sludge and prepared activated carbon with NaOH chemical activation at pyrolysis temperatures of 500 °C and 600 °C.