Addressing the critical issue of water pollution, this review article emphasizes the need to remove hazardous dyes and phenolic compounds from wastewater. These pollutants pose severe risks due to their toxic, mutagenic, and carcinogenic properties. The study explores various techniques for the remediation of organic contaminants from wastewater, including an enzymatic approach. A significant challenge in enzymatic wastewater treatment is the loss of enzyme activity and difficulty in recovery post-treatment. To mitigate these issues, this review examines the strategy of immobilizing enzymes on newly developed nanostructured materials like graphene, carbon nanotubes (CNTs), and metal–organic frameworks (MOFs). These materials offer high surface areas, excellent porosity, and ample anchoring sites for effective enzyme immobilization. The review evaluates recent research on enzyme immobilization on these supports and their applications in biocatalytic nanoparticles. It also analyzes the impact of operational factors (e.g., time, pH, and temperature) on dye and phenolic compound removal from wastewater using these enzymes. Despite promising outcomes, this review acknowledges the challenges for large-scale implementation and offers recommendations for future research to tackle these obstacles. This review concludes by suggesting that enzyme immobilization on these emerging materials could present a sustainable, environmentally friendly solution to the escalating water pollution crisis.

Drilling fluids are the core of drilling operations, and they are responsible for many roles, such as lubricating drill string, cooling down drilling equipment, maintaining wellbore integrity, and transporting cuttings to the surface. High-energy demands have caused the oil and gas production rates to increase by orders of magnitude, which is accompanied by increased usage of different drilling fluids, including oil-based muds (OBM) and water-based muds (WBM). Large amounts of fluids used without caution can cause severe consequences to the environment if not well monitored. Therefore, the field has been exploring the utilization of biodegradable and environmentally friendly additives (green). These green formulations can promote a safer alternative to the currently available commercial additives, meet sophisticated drilling requirements, and ensure resource sustainability. A comprehensive overview of the literature has been conducted in this review, starting with a background on oil and gas reservoir types and cuttings transportation mechanisms, followed by a discussion on various recent green fluids or additives emerging in the field. In addition, an economic comparison has been conducted to assess the feasibility of the reviewed green formulations. Finally, the review ends with a summary and future prospective on the topic. In conclusion, this review suggests the development of multifunctional drilling fluids with good hole-cleaning properties, utilizing additives studied for different functions (e.g., filtration). Enhancement of rheological properties achieved through the addition of these additives indicates their suitability for hole-cleaning applications, which must be confirmed through additional studies. Consequently, filling the existing gap in the literature is by triggering research topics in this area.

Fibers are extensively used as a fluid additive in the oil and gas industry to improve hole-cleaning performance, control fluid filtration loss, and enhance hydraulic fracturing effectiveness. Generally, a small amount of fiber is dispersed in the base fluid to achieve the desired results without increasing the viscosity of the base fluid. Nevertheless, sustaining a uniform fiber dispersion can be challenging under wellbore conditions, which is essential for fibers’ functionality. Consequently, a better understanding of fiber suspension or stability in base fluids is necessary for their efficient utilization in drilling and completion operations. In this study, response surface methodology (RSM) and box–behnken design (BBD) are used to investigate the stability of fiber in polymeric base suspensions, including carboxy methyl cellulose (CMC), polyacrylamide (PAM), and xanthan gum (XG). The BBD of three factors was selected to observe the influence of polymer concentration, fiber concentration, and temperature on fibrous suspension stability, with three levels of design factors (low, mid, and high) and two fiber aspect ratios (3 and 12 mm fibers). The base fluid polymer concentration ranged from 1 to 8 vol %, fiber concentration ranged from 0.01 to 0.08 wt %, and the temperature was varied from 25 to 80 °C. The stability measurements were analyzed using Minitab, subsequently, evaluating the factors’ impact and interactions and determining the optimum conditions for the stability of the fibrous suspensions. The results predicted by the developed model were in good agreement with the experimental results R² ≥ 0.91–0.99. The sensitivity analysis showed that base fluid polymer concentration is the most significant factor affecting fibrous suspension stability. At high polymer concentrations, fiber concentration and temperature effects are minimal, while the temperature effect on the stability was observed at low concentrations (e.g., low suspension viscosities). The fiber aspect ratio indirectly affects system stability. Long fibers have a better tendency to entangle and form a structured network, which in turn hinders the buoyancy that induces individual fiber migration. On the contrary, short fibers do not form a network, allowing them to easily migrate to the surface and agglomerate at the top layer (unstable region). Optimization results revealed that suspensions with viscosities above 50 mPa·s are sufficient to maintain the stability of the suspensions at ambient (25 °C) and elevated (80 °C) temperatures.

Produced water (PW) is the most significant waste stream generated in the oil and gas industries. The generated PW has the potential to be a useful water source rather than waste. While a variety of technologies can be used for the treatment of PW for reuse, biological-based technologies are an effective and sustainable remediation method. Specifically, microalgae, which are a cost-effective and sustainable process that use nutrients to eliminate organic pollutants from PW during the bioremediation process. In these treatment processes, microalgae grow in PW free of charge, eliminate pollutants, and generate clean water that can be recycled and reused. This helps to reduce CO₂ levels in the atmosphere while simultaneously producing biofuels, other useful chemicals, and added-value products. As such, this review focuses on PW generation in the oil and gas industry, PW characteristics, and examines the available technologies that can be used for PW remediation, with specific attention to algal-based technologies. In addition, the various aspects of algae growth and cultivation in PW, the effect of growth conditions, water quality parameters, and the corresponding treatment performance are presented. Lastly, this review emphasizes the bioremediation of PW using algae and highlights how to harvest algae that can be processed to generate biofuels for added-value products as a sustainable approach.

Particles size distribution (PSD) is introduced as a tool for analysis of bentonite aggregation and swelling kinetics. Raw Ca-bentonite was purified using a combined wet sieving and sedimentation processes, followed by thermochemical treatment with Na₂CO₃ to increase its swelling capacity. The detailed analysis of the PSD shows a strong correlation between the PSD and the swelling process. For the chemically treated raw bentonite, PSD revealed two different peaks representing unswelled and swelled particles along with some aggregates. The swelling is shown to be a kinetically controlled process that depends on time, temperature, and bentonite chemical composition. At the beginning of the chemical treatment, the effect of aggregates was more dominant; therefore, the viscosity did not increase much with particle size. However, the combined chemical and thermal treatment has enhanced the Na-activation process and boosted bentonite swelling. The rheological measurements have shown enhancement in the viscosity and confirmed the PSD findings. The same optimal treatment conditions are obtained from both rheological measurements and PSD analysis. A model is developed based on classical reaction rate kinetics and used to describe the conversion from unswelled to swelled particles. The PSD has a strong correlation with the physical properties of the suspension such as the viscosity. The swelling rate fits a second order model with a rate constant, k, in the range 0.002 to 0.124 h⁻¹ and an activation energy, E, of 87 kJ/mol. PSD analysis together with the developed kinetic model are powerful tools for studying the swelling kinetics of bentonites. Graphical Abstract