The growing impact of anthropogenic activities, including urbanization, agriculture and industrial expansion, has intensified water and environmental pollution, and wastewater treatment has evolved beyond pollutant removal toward the recovery of nutrients, energy and high-value materials. This work is a critical review supported by a systematic search and selection procedure: Scopus, Web of Science Core Collection and Google Scholar were searched for English-language records published between January 2015 and March 2026, using Boolean combinations of technology, treatment-performance and resource-recovery terms (final search 28 March 2026). Of 1142 records identified, 318 were assessed at full text and 102 studies met the predefined inclusion criteria and were synthesised, with evidence weighted by reactor scale and matrix realism so that results obtained with synthetic solutions are never presented as full-scale performance. Technologies are compared only on normalised criteria, and a system boundary is stated for every energy value. Three comparative findings emerge. First, biological systems achieve the highest carbon-removal performance at the lowest specific energy demand, but they eliminate nitrogen mainly as N2, which prevents pollution without retaining nitrogen in a reusable material pathway. Second, physicochemical and nanomaterial-based systems achieve the highest selectivity and product purity, but their net energy benefit is frequently negative once oxidant, photon and sorbent-regeneration inputs are accounted for. Third, hybrid configurations improve removal efficiency and reduce footprint, but they transfer the cost from energy to operational complexity and control requirements. The review provides process engineers and decision-makers with comparative criteria for technology selection and identifies explicitly where the current evidence base is insufficient to support claims of net energy gain, low lifecycle impact or economic feasibility. The technologies discussed are relevant to SDG 6, SDG 9 and SDG 12; however, the reviewed literature does not quantify the contribution of any individual technology to these goals, and no claim of measurable progress towards them is made in this work.
The presence of inorganic and organic pollutants into water environment has become global serious concern. The wastewater discharged from food, textiles, leather, plastic, paper, cosmetic and pharmaceutical industries introduce both cationic and anionic dyes in natural and synthetic forms into the water bodies. Cationic dyes are considered more toxic and problematic in wastewater than anionic dyes due to their positive charge which strongly binds to the negatively charged biological molecules leading to greater cellular damage, possible carcinogenicity and environmental persistence, thus, posing major threats to aquatic life and human health. Several conventional processes have been utilized for the degradation of cationic dyes, among which photocatalysis using nanomaterials and nanocomposites stands out as a promising technology. These nano-based structured materials with properties of semiconductor are excellent photocatalyst both under UV and visible light radiation. This present review discussed the recent advances in performance of various critically assessed reported nanomaterials in degradation of cationic dyes. A detailed evaluation of articles published on photocatalytic degradation of toxic cationic dyes was presented depicting different functionalization strategies, architectural structures of the nanostructured materials. Photocatalytic performance, degradation mechanism and stability of the nano-based catalyst were also outlined extensively. In addition, limitations and future outlook were discussed with a focus on the development of novel strategies to further improve the effectiveness and sustainability of nanostructured photocatalysts for cationic dye degradation. This review presents a significant perspective on existing studies towards efficient photocatalytic degradation of cationic dyes using nanocomposites due to increase in pollution of water ecosystem. Also, the review will guide the future researchers to find solutions to environmental problems and sustainable wastewater management.
The aim of this study is to experimentally investigate the vibro-acoustic behavior of a single-cylinder compression ignition engine fuelled with ternary blends of Ricinus communis L. biodiesel, n-butanol and graphene oxide nanoparticles with special emphasis on the effect of injection timing. Experiments were performed at injection timings of 21°, 23° and 25° bTDC. The vibration velocity of the engine was measured by Laser Doppler Vibrometry and the noise characteristics were evaluated based on sound pressure level measurements. The vibro-acoustic responses of the fuel blends studied were comparatively evaluated at different injection timings. With the injection timing advanced, the diesel vibration velocity was reduced from 0.843 m/s to 0.467 m/s. Among the blends of nanoparticles, the D65B20nB15 + 75 ppm NPs blend produced a minimum vibration velocity of 0.156 m/s at 25° bTDC, which is 81.5% lower than that of diesel at 21° bTDC. The D70B20nB15 blend showed vibration reductions of 22.0%, 19.7% and 66.6% at 21°, 23° and 25° bTDC respectively. The sound pressure levels also decreased from 70.37 dB to 58.33 dB with advanced injection timing. The minimum RMS noise of 54.20 dB was achieved for D65B20nB15 + 75 ppm NPs at 25° bTDC. The results show that the fuel composition combined with the optimization of the injection timing can have a significant influence on the vibration and noise characteristics of the engine. Of the conditions tested, the D65B20nB15 + 75 ppm NPs at 25° bTDC provided the best overall vibro-acoustic response, suggesting it can be used to reduce engine vibration and noise under the experimental conditions studied.
Load shedding in South Africa has severely hindered governance and the operation of critical urban infrastructures, such as government complexes, leading to frequent interruptions in public service delivery. While solar photovoltaic (PV) microgrids are recognised as a viable alternative to grid dependency, most existing research focuses on rural or residential applications, leaving a gap for site-specific assessments of urban office buildings that prioritize service continuity during grid instability. This study investigates the design and optimisation of a hybrid microgrid, integrating solar PV, battery storage, diesel backup, and a grid connection, to meet the power requirements of a government office complex in Johannesburg. Using Hybrid Optimisation Model for Electric Renewables (HOMER) Pro software and recorded hourly consumption data, the system was modelled by employing a load-following dispatch strategy alongside simultaneous multi-objective optimisation for cost and environmental impact. The study reported PV-Battery-Grid (PV-B-GR) configuration as the optimal solution. This configuration yielded a Levelized Cost of Energy (LCOE) of ZAR1.11 and a Net Present Cost (NPC) of ZAR1, 842,856. While its operating costs are slightly higher than configurations with heavier generator use, it provides the lowest emissions of pollutants such as CO₂, CO, SO₂, and NOx. This study provides a framework for achieving energy independence in commercial buildings, while offering a scalable roadmap for policymakers to mitigate the impact of the South African energy crisis and replicate it for other climes.
Water-induced soil erosion threatens agricultural land and water resources across the Kashmir Himalaya, where steep terrain, expanding horticulture and climate variability interact under uncertain future conditions. This study combines the Revised Universal Soil Loss Equation (RUSLE), CA–Markov land-use projections and a four-model CMIP6 ensemble to produce spatially explicit, scenario-based estimates of average annual sheet and rill soil loss across the Kashmir Valley for 2005, 2010, 2015 and 2020 and for the future horizons 2030, 2050 and 2070 under SSP2–4.5, SSP3–7.0 and SSP5–8.5. Rainfall erosivity was derived from 41 years of monthly station records using the Modified Fournier Index. Historical domain-wide mean soil loss ranged from 8.57 to 14.31 t ha⁻¹ yr⁻¹ and did not change monotonically; the Extreme class (>50 t ha⁻¹ yr⁻¹) expanded from 186,415 ha in 2005–246,699 ha in 2020. For 2070, projected means are 8.12, 4.36 and 2.41 t ha⁻¹ yr⁻¹ under SSP2–4.5, SSP3–7.0 and SSP5–8.5, respectively, while the corresponding pixel maxima are 175.69, 185.65 and 187.63 t ha⁻¹ yr⁻¹ . A raster-based CA–Markov hindcast of 2020 from the 2005–2015 transitions yielded a Figure of Merit of 0.160 and Kappa of 0.475. Overall agreement (0.569) was below the no-change persistence benchmark (0.662); therefore, the future LULC outputs are interpreted as conditional scenarios with substantial allocation uncertainty. Recurrent high-value areas in the northeastern and southwestern highlands are candidates for field verification and targeted conservation.
