The pretreatment effects of various target pollutant in real coal gasification gray water by coupling pulse electrocoagulation with chemical precipitation methods

The simultaneous removal of methylene blue (MB) and Ca2+ by recyclable adsorbents based the scales derived from coal gasification system

The transformation of solid wastes from industrial production into effective adsorbents could significantly contribute to wastewater treatment. In this study, after acidizing and burning soft scale (SS) from coal gasification system, two magnetic adsorbents (mag-ASS and mag-BASS) were prepared via the combination of magnetite with ultrasonic, respectively. The treatment effects of mag-ASS and mag-BASS were then investigated for simulated wastewater containing macromolecular organic matter [i.e., methylene blue (MB)] and Ca2+. The results indicated that the pseudo second order kinetic, Elovich, Freundlich, Langmuir and Temkin model could well describe the adsorption behavior of MB and Ca2+ onto mag-ASS and mag-BASS. The maximum adsorption capacities of mag-ASS for MB and mag-BASS for Ca2+ were 600.53 mg/g and 102.54 mg/g, respectively. Surprisingly, the adsorption abilities of mag-ASS for MB and mag-BASS for Ca2+ show significantly higher than the others. The adsorption mechanisms of MB mainly included electrostatic interaction, π-π conjugate interaction and cation exchange, while those of Ca2+ were mainly electrostatic interaction and cation exchange. The diffusion of MB and Ca2+ onto the magnetic adsorbents might be controlled by the combined effects of intraparticle and liquid film diffusion. There was no significant reduction in adsorption capacity after 8 cycles of adsorption and desorption, indicating that SS-based magnetic adsorbents had good recyclability and stability. Moreover, the removal efficiency of mag-BASS for total hardness and total organic carbon in real coal gasification gray water (CGGW) was 82.60 and 64.10%, respectively. The treatment of CGGW and the resource of wastes would significantly promote the reasonable disposal of coal gasification scales.

Advancements in combined electrocoagulation processes for sustainable wastewater treatment: A comprehensive review of mechanisms, performance, and emerging applications

This review explores the potential and challenges of combining electrochemical, especially electrocoagulation (EC) process, with various - wastewater treatment methods such as membranes, chemical treatments, biological methods, and oxidation processes to enhance pollutant removal and reduce costs. It emphasizes the advantages of using electrochemical processes as a pretreatment step, including increased volume and improved quality of permeate water, mitigation of membrane fouling, and lower environmental impact. Pilot-scale studies are discussed to validate the effectiveness of combined EC processes, particularly for industrial wastewater. Factors such as electrode materials, coating materials, and the integration of a third process are discussed as potential avenues for improving the environmental sustainability and cost-effectiveness of the combined EC processes. This review also discusses factors for improvement and explores the EC process combined with Advanced Oxidation Processes (AOP). The conclusion highlights the need for combined EC processes, which include reducing electrode consumption, evaluating energy efficiency, and conducting pilot-scale investigations under continuous flow conditions. Furthermore, it emphasizes future research on electrode materials and technology commercialization. Overall, this review underscores the importance of combined EC processes in meeting the demand for clean water resources and emphasizes the need for further optimization and implementation in industrial applications.

Porphyrin/phthalocyanine-based porous organic polymers for pollutant removal and detection: Synthesis, mechanisms, and challenges

The growing global concern about environmental threats due to environmental pollution requires the development of environmentally friendly and efficient removal/detection materials and methods. Porphyrin/phthalocyanine (Por/Pc) based porous organic polymers (POPs) as a newly emerging porous material are prepared through polymerizing building blocks with different structures. Benefiting from the high porosity, adjustable pore structure, and enzyme-like activities, the Por/Pc-POPs can be the ideal platform to study the removal and detection of pollutants. However, a systematic summary of their application in environmental treatment is still lacking to date. In this review, the development of various Por/Pc-POPs for pollutant removal and detection applications over the past decade was systematically addressed for the first time to offer valuable guidance on environmental remediation through the utilization of Por/Pc-POPs. This review is divided into two sections (pollutants removal and detection) focusing on Por/Pc-POPs for organic, inorganic, and gaseous pollutants adsorption, photodegradation, and chemosensing, respectively. The related removal and sensing mechanisms are also discussed, and the methods to improve removal and detection efficiency and selectivity are also summarized. For the future practical application of Por/Pc-POPs, this review provides the emerging research directions and their application possibility and challenges in the removal and detection of pollutants.

Integrating of electrocoagulation process with submerged membrane bioreactor for wastewater treatment under low voltage gradients

Treating and reusing wastewater has become an essential aspect of water management worldwide. However, the increase in emerging pollutants such as polycyclic aromatic hydrocarbons (PAHs), which are presented in wastewater from various sources like industry, roads, and household waste, makes their removal difficult due to their low concentration, stability, and ability to combine with other organic substances. Therefore, treating a low load of wastewater is an attractive option. The study aimed to address membrane fouling in the submerged membrane bioreactor (SMBR) used for wastewater treatment. An aluminum electrocoagulation (EC) device was combined with SMBR as a pre-treatment to reduce fouling. The EC-SMBR process was compared with a conventional SMBR without EC, fed with real grey water. To prevent impeding biological growth, low voltage gradients were utilized in the EC deviceThe comparison was conducted over 60 days with constant transmembrane pressure and infinite solid retention time (SRT). In phase I, when the EC device was operated at a low voltage gradient (0.64 V/cm), no significant improvement in the pollutants removal was observed in terms of color, turbidity, and chemical oxygen demand (COD). Nevertheless, during phase II, a voltage gradient of 1.26 V/cm achieved up to 100%, 99.7%, 92%, 94.1%, and 96.5% removals in the EC-SMBR process in comparison with 95.1%, 95.4%, 85%, 91.7% and 74.2% removals in the SMBR process for turbidity, color, COD, ammonia nitrogen (NH3-N), total phosphorus (TP), respectively. SMBR showed better anionic surfactant (AS) removal than EC-SMBR. A voltage gradient of 0.64 V/cm in the EC unit significantly reduced fouling by 23.7%, while 1.26 V/cm showed inconsistent results. Accumulation of Al ions negatively affected membrane performance. Low voltage gradients in EC can control SMBR fouling if Al concentration is controlled. Future research should investigate EC-SMBR with constant membrane flux for large-scale applications, considering energy consumption and operating costs.