Environmental Technology最新文献

In this study, waste cooking oil was subjected to heterogeneous transesterification using a graphitic carbon nitride (g-C₃N₄) nanocatalyst, with the primary aim of developing a sustainable and cost-effective catalytic system for biodiesel production. The catalyst was synthesized by annealing urea at 500°C for 4 h and characterized using X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. For biodiesel synthesis, WCO was initially esterified to reduce free fatty acids, followed by transesterification using the g-C₃N₄ under various reaction conditions. The Box-Behnken Design coupled with Response Surface Methodology was employed to optimize the critical transesterification parameters, including catalyst concentration, reaction temperature, and reaction time. The developed model demonstrated a high R² value (0.9998), indicating excellent precision and minimal prediction error, thereby confirming its robustness. Under optimized conditions (catalyst dosage = 1.75 wt.%, reaction temperature = 60°C, and reaction time 70 min), a maximum fatty acid methyl ester yield of 89.16% was achieved. Gas chromatography-mass spectrometry and FTIR confirmed the successful conversion of triglycerides into FAME. Physicochemical properties of the biodiesel met the American Society for Testing and Materials standards, validating its suitability as a renewable fuel. The key finding of this study is that the g-C₃N₄ exhibits excellent catalytic activity with relatively low catalyst loading, thereby offering a promising alternative to conventional catalysts. Future research is necessary to examine the long-term stability, reusability of the catalyst, assess large-scale viability, and conduct thorough life-cycle and techno-economic evaluations to determine its sustainability in commercial biodiesel production.

Soil acidity, specifically the presence of Al ^+ 3 at toxic levels for most crop plants, is one of the main factors limiting agricultural production. However, the relationship between organic acid exudation and its direct influence and magnitude on aluminium tolerance in rice plants remains poorly elucidated in the literature. In order to verify the complexing effect of organic acids on Al, trials were carried out with rainfed rice seedlings of the Comum Branco and Caiapó varieties, under controlled growth conditions, in addition to evaluating the exudation of organic acids and possible changes in their internal root contents as a function of Al. It can be concluded that citric acid was effective in mitigating the toxic effects of Al³⁺ on the root system of the evaluated rice cultivars. In the absence of aluminium, malic acid promoted an increase in root length. The cultivar Comum Branco exhibited a greater tolerance to Al³⁺ compared to Caiapó, which may be associated with its higher exudation and accumulation of organic acids in the roots. These results suggest that the action of these mechanisms contributes to the greater aluminium tolerance observed in this cultivar.

Microplastics (MPs) and nanoplastics (NPs) have attracted widespread attention due to their detrimental effects on the ecosystem and human health. NPs, which are smaller and more harmful than MPs, are generated during the degradation of MPs. The present study aimed to inhibit the release of polyvinylchloride NPs (PVC-NPs) generated during the degradation of PCV-MPs, by using Ultraviolet/ sulphite (UV/SO₃^2-) in the presence of O₂ (UV/SO₃^2-/O₂). Under optimal conditions, the dechlorination rate and weight loss of PVC-MP were 72.4% and 61.7%, respectively. The chemical changes of the treated PVC-MPs and the intermediates during the degradation of PVC-MPs were investigated. It was confirmed that PVC-NPs form during the degradation PVC-MPs. In addition, PVC-NPs were successfully removed from the water by superoxide ion (O₂^-)-induced self-flocculation, resulting in a reduced release of PVC-NPs into the water. The weight of the self-flocculation containing PVC-NPs was 5.2 mg. Self-flocculation was investigated by scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Numerous C-O-C groups were identified in the self-flocculation. The results indicate a potential process for the removal of PVC-NPs by self-flocculation. This study introduces a new method of degradation of PVC-MPs while simultaneously reducing the release of PVC-NPs.

Nowadays, the presence of triazine-based azo dyes like Reactive Red 120 (RR 120) in textile wastewater poses a significant hazardous environmental impact, deteriorating the aquatic biota and requiring an effective treatment method. Compared to conventional energy-intensive and secondary waste-generating physicochemical methods, biological methods, especially microbial biodegradation, offer a sustainable, eco-friendly, and cost-effective alternative for the treatment of effluents containing dye-laden wastewater. This study evaluated the efficacy of Bacillus tequilensis MCC2908 for biodegradation and detoxification of RR 120 using a continuously Packed Bed Bioreactor (PBBR). The experimental findings revealed an optimum range of ILR within 75-85 mg/L.day, achieving 94.2 ± 2.71% RE and 24.1 ± 1.205 mg/L.day EC, avoiding limitations imposed by mass transfer and bioreaction, and maintaining a robust and efficient bioreactor system. Crystal Violet staining test confirmed the quantitative assessment of biofilm growth, while SEM images made it observable on the polyurethane bio-carrier. The FTIR spectra confirmed the biodegradation of RR 120, showing significant changes in the functional groups. The detoxification was demonstrated using bacterial and phytotoxicity, validating the toxicity reduction, further duly supported by photosynthetic pigment analysis. The Monod model and the Andrew-Haldane kinetics significantly described microbial growth under non-inhibitory and inhibitory conditions, respectively. Nevertheless, the present findings not only highlighted the potential of biofilm-based PBBR but also delivered an eco-friendly, sustainable solution for the remediation of textile wastewater. Future studies may explore the scaling up of this biotechnological solution for the mitigation of industrial challenges and establish hybrid approaches to further enhance biodegradation efficiency.HighlightsPBBR significantly achieved efficient biodegradation and detoxification of RR 120.An optimum ILR of 75-85 mg/L.day exhibited the best operating conditions for PBBR.Microbial biomass and biofilm formation were quantified using the Crystal Violet Staining method.Phytotoxicity, photosynthetic pigment analysis, and bacterial toxicity unveiled the RR 120 detoxification.Moderate K_i and low K_s values depicted the resilience and high microbial activity for RR 120.

The preparation of activated carbon derived from municipal sludge and amino modification for CO₂ adsorption can not only achieve the resource utilization of sludge but also address the issue of CO₂ emission reduction. Municipal sludge was used in this study as a raw material to prepare CO₂ adsorbents via pyrolysis, activation, and amino modification. Microstructural characterization and CO₂ performance tests were conducted to analyze the influence of different activation agents, pyrolysis temperature, and pyrolysis time on the microstructural evolution and CO₂ adsorption performance of sludge-based activated carbon. The results indicate that the solid NaOH activator enabled the sludge to generate more pore structures. When the pyrolysis temperature was 600°C and the pyrolysis time was 60 min, an excellent pore structure was obtained. Nevertheless, an excessively high pyrolysis temperature and time would cause sintering of the samples, leading to pore collapse. Under the aforementioned preparation conditions, the sludge-activated carbon reached its maximum CO₂ adsorption capacity, with the maximum adsorption capacity of CO₂ being 1.369 mmol/g. The adsorption temperature had a significant influence on the final adsorption effect, and the optimal adsorption temperature is 25°C.

Aqueous contamination by arsenic and antimony has become a significant concern due to its prevalence in smelting activities. Nowadays, adsorption stands out as an effective method for the removal of these heavy metal ions from water, particularly when the goal is to achieve high levels of purification and ensure safety. However, the complex nature of smelting wastewater often leads to a decrease in the selectivity and salt resistance of adsorbents under industrial conditions. In this study, we introduce a novel designated composite-resin material (KYE003), which is tailored for the deep purification of arsenic and antimony. By precisely adjusting the synthesis ratios, we have controlled the intrinsic kinetics of material synthesis, enabling the in-situ loading of ferric oxide onto the resin surface, coupled with organic functional groups (-COOH and -SH). The resin's inherent porous structure not only promotes the nucleation and growth of amorphous iron oxide but also establishes a quantitative basis for nano-scale binding sites. Further surface characterisation analysis indicates that interfacial functional groups, including (-COOH, -SH, and -OH), are instrumental in the complexation of arsenic and antimony. The synergistic interactions, such as -O-As/Sb, -COO-As/Sb, and -S-As/Sb, demonstrate that the hybridisation of these groups restructures the interfacial electronic state, thereby enhancing the adsorption performance. The KYE003 material exhibits exceptional adsorptive selectivity and chemical stability under complex conditions, capable of maintaining arsenic concentrations in the effluent below 20 µg·L^-1 until the bed volumes ratio surpasses 6240. This research presents a new perspective for the deep purification of heavy metal ions.

Vermicomposting has been proven to be effective in combating tetracycline resistance genes (TRGs) in organic waste, such as animal manure and sewage sludge. However, the influences of tetracycline resistant bacteria (TRB) in organic waste during earthworm conversions on the fate of TRGs remain poorly understood. Hence, we prepared diets treated with either sensitive or insensitive tetracycline resistant bacteriome (STRB or ITRB) to earthworm midgut fluid and investigated the fate of bacterial communities and TRGs (including tetB, tetC, tetZ, tetL, and tetX) and their response to tetracycline during earthworm conversions in a controllable environment. Results showed that the bacterial composition of casts was highly complex, yet diet-derived bacteria were either minimal or undetectable. Notably, TRGs abundance in casts was dramatically higher than that in diets, indicating that the earthworm gut is a hotspot for TRGs dissemination. Furthermore, the increase in TRGs abundance was more pronounced in casts treated with ITRB compared to those treated with STRB, and this increase was suppressed by tetracycline exposure in casts treated with ITRB. This phenomenon may be due to the fact that diet-derived TRB and/or tetracycline alter the microbial community (e.g. relative abundance of Aeromonas). In conclusion, this study highlights the diet-derived TRB amplify the hotspot effect of earthworm gut on tetracycline-resistance gene dissemination, but regulated by tetracycline.

This study aimed to evaluate the bioleaching of copper from discarded printed circuit boards (PCBs) using the fungus Aspergillus tubingensis UCP 1208 as a sustainable and environmentally friendly alternative for the recovery of valuable metals. The methodology included the acclimatization of the fungus to different concentrations of crushed PCBs, followed by bioleaching assays and copper removal analysis through scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) and inductively coupled plasma optical emission spectrometry (ICP-OES). SEM-EDS analyses revealed significant changes in the morphology and elemental composition of the PCBs after treatment, confirming the efficiency of copper solubilization. Quantitative results indicated that A. tubingensis, acclimatized with 1% (w/v) of crushed PCBs, removed 494.2 mg L⁻¹ of copper for a PCB load of 1 g L⁻¹, representing a 335.5% increase in removal compared to conventional acid digestion. These results demonstrate that bioleaching with A. tubingensis is a viable, efficient, and sustainable approach for the recovery of metals from electronic waste, offering a cleaner alternative to traditional chemical methods by avoiding the use of aggressive acids and contributing to circular economic practices.

For the biological treatment of swine wastewater, accelerating the degradation of COD usually leads to increased microbial nitrification, resulting in a conflict between pollutant removal and nitrogen recycling. In this study, the addition of hematite-biochar mixture and the nitrification inhibitor dicyandiamide (DCD) was proposed and applied to simultaneously enhance COD removal and nitrogen recycling efficiency in a Myriophyllum aquaticum-based swine wastewater treatment process. The results showed that addition of hematite-biochar mixture achieved a 1 times increase on COD removal rate. Meanwhile, the addition of DCD effectively suppressed microbial nitrification but slightly increased nitrogen removal by enhancing nitrogen utilization with Myriophyllum aquaticum. Eventually, the addition of hematite-biochar and DCD simultaneously improved the COD removal and nitrogen recycling rate to 96.9% (vs. 46.6% for control) and 72.8% (vs. 39.9% for control), respectively. Furthermore, microbial community analysis indicated that the developed strategy enhanced the abundance of Firmicutes and the genus Comamonas (strengthening COD removal), while reducing the abundance of nitrifying bacteria (phylum Proteobacteria) (repressing the nitrification process). This work provided a practical approach to accelerate pollutants removal while preserving nitrogen for plant utilization, which would be a promising solution for nitrogen recycling from swine wastewater.

Microalgae are considered promising for wastewater treatment and nutrients recovery. However, microalgae from wastewater usually have a high ash content, which significantly influences on the utilization efficiency of microalgae. In this study, poultry wastewater with different salinity levels was used to cultivate Chlorella sp. in bench-scale ponds. The ion content of the microalgal ash was tested to determine the composition of the ash. The results show that microalgae cultivated in wastewater with higher salinity results in a high ash content, and the ash content of microalgae from fertilizer wasterwater (FW) has a positive linear relationship with the initial salinity of FW. The ash content of microalgae in wastewater with 3.59 g L^-1 salinity is 12.5% higher than that in wastewater with 1.50 g L^-1 salinity. The main compounds of microalgal ash from FW runs were CaO, P₂O₅, MgO, SiO₂, and K₂O (over 5%). The highest removal rates of NH₄⁺-N, TP, and TOC in the FW runs were 99.1%, 93.7%, and 80%, respectively. Except for FW-16, the lipid and protein contents of microalgae from FW runs showed a positive relationship with the dilution ratios. This research aims to propose a way to reduce the microalgae ash when coupling microalgae cultivation with the wastewater.