Abstract Industrial discharge of dye-containing effluents into aquatic environments poses severe ecological and human health risks because of their toxicity, persistence, and potential carcinogenicity. Among different dye classes, cationic dyes are particularly difficult to eliminate due to their high solubility, chemical stability, and strong electrostatic interactions in aqueous media. Photocatalysis has emerged as an efficient and sustainable approach for degrading toxic organic pollutants under light irradiation. This review comprehensively discusses the classification of cationic dyes and recent advances in photocatalytic wastewater treatment technologies. Special emphasis is placed on visible-light-active photocatalysts, including heterojunction nanocomposites, metal and nonmetal doped semiconductors, and bio-inspired materials, which exhibit enhanced light absorption, improved charge separation, and superior photocatalytic stability. The review further highlights the influence of operational parameters and integrated treatment strategies on degradation efficiency. In addition, critical challenges related to catalyst recovery, long-term stability, cost-effectiveness, and practical applicability in real wastewater systems are discussed, together with future research perspectives for sustainable environmental remediation. Mechanistic pathways involving reactive oxygen species generation and electron–hole separation are also summarized to explain enhanced photocatalytic degradation performance under visible light irradiation.
Abstract The phenomenon of acoustic cavitation (the formation, oscillation, growth, and implosive collapse of tiny bubbles filled with dissolved gases and liquid vapor) generated by the irradiation of a liquid medium with ultrasound has established itself as an important tool in various branches of chemistry. The use of ultrasonic irradiation in chemical processes is known as “sonochemistry.” Among the applications of sonochemistry, the involvement of ultrasound in materials synthesis can provide a fast, straightforward method for preparing heterogeneous catalysts compared to conventional methods, thanks to the chemical and physical effects of acoustic cavitation (excited species, shockwaves, microjets, sonoluminescence). The catalytic processes involved in the transformation of greenhouse gases are attracting greater attention for their role in addressing the major environmental problem of global warming. The application of ultrasonic irradiation results in catalysts with enhanced structural, textural, and morphological properties, including specific surface area, particle size distribution, and dispersion of the active phase on the support. Hence, ultrasonic-assisted synthesis of catalysts yields materials with better activity and stability than those obtained by classical preparation methods, which is particularly important for the development of heterogeneous catalysis.
Abstract High sulfur content in fuel oil drives SOx emissions and equipment corrosion, necessitating advanced desulfurization to meet IMO 2020 (0.5 wt%) and USEPA (10–15 ppm) standards. This review critically evaluates six methods – hydrodesulfurization (HDS), oxidative (ODS), adsorptive (ADS), extractive (EDS), biodesulfurization (BDS), and electromagnetic desulfurization (EMDS) – focusing on EMDS–ODS–ADS hybrids for heavy fuels. EMDS uses high-frequency magnetic fields and ferromagnetic nanoparticles for up to 85 % sulfur removal under mild conditions (25–250 °C, 1–5 bar). Hybrids excel in lab-scale tests, yet ODS drops from 100 % (model fuels) to 58.54 % (heavy oil), revealing matrix effects (25–40 % loss). No continuous EMDS-hybrid pilots exist for real heavy crudes. EMDS challenges include nanoparticle aggregation (3–5 cycles), field energy demands, and costs, requiring techno-economic validation. Quantitative analysis of oxidant stoichiometry (rox = 1.0–3.0), energy-normalized metrics, stability, and biotoxicity shows HDS–ODS as near-term industrials, EMDS-hybrids precommercial. Future roadmap prioritizes recyclable EMDS catalysts, heavy-fuel pilots (1 bbl/d, 18–36 months), and HDS life-cycle comparison – without real-feedstock data, laboratory claims systematically overestimate industrial viability.
Abstract The high alkalinity and fine particle size of red mud, coupled with its complex symbiosis, can result in land salinization, as well as water and air pollution and the risk of dam failure. When stockpiled in the open air, it poses a potential threat to human health and safety. To mitigate the adverse effects of red mud, efficacious dealkalization technologies must be developed and implemented to reduce its alkalinity and improve its utilization as a resource. This article reviews traditional and emerging methods for alkali removal, including water washing, lime treatment, acid treatment, salt substitution, and industrial waste liquid neutralization; meanwhile, new methods such as microbial method, membrane sodium removal technology, calcium slag method, calcification carbonation method, and microwave treatment method are introduced. The paper summarizes and compares the advantages and disadvantages of these technologies, highlighting that the future challenge lies in achieving the industrial application of red mud alkali removal technology that balances economy, environmental protection, and efficiency. It also indicates that future development should focus on efficiently recovering strategic metals (such as iron, aluminum, titanium, scandium) from red mud while removing the alkali, ultimately realizing the utilization and reduction of red mud.
Abstract Sustainable development has become a necessity in conventional cement production to reduce environmental impact. Global demand needs to reduce greenhouse gas (GHG) emissions. The transition to green cement manufacturing plays a key role in achieving net-zero carbon dioxide (CO 2 ) emissions and carbon-neutral concrete by 2050. This patent review highlights the importance and potential of green cement manufacturing through an electrochemical process, converting calcium carbonate (CaCO 3 ) into calcium hydroxide Ca(OH) 2 to produce ordinary Portland cement. This study reveals the entire patent landscape in green cement production and electrochemical green cement production. It highlights and describes the notable patents and their methodology. In addition, this review assesses the innovation of electrochemical technology in cement manufacturing and its potential and feasibility. A roadmap with efficient and effective polices and a framework can enhance the production of green cement. It can be expected that incorporation of electrochemical technology for calcium hydroxide production, when paired with renewable resources, cannot only reduce the overall emission and carbon footprint of cement products but also contribute toward achieving sustainable development goals, mitigate climate change, and regulate the market trend toward more sustainable products. It has been proven that interdisciplinary collaboration is indeed a necessity to overcome the technical and regulatory barriers.
