Environmental Technology最新文献

ABSTRACTDrought presents a major challenge to the management of rocky desertification and ecological restoration in the delicate karst ecosystems of Guangxi. In this study, the normalized difference vegetation index (NDVI), fractional vegetation cover (FVC) and net primary productivity (NPP) were selected as vegetation remote sensing parameters, and the spatial response characteristics of different types of vegetation in karst areas of Guangxi Province to light, moderate, severe and extreme drought were analyzed to provide scientific basis for the evaluation of the impact of drought on vegetation in karst areas. The results are as follows: (1) NDVI, FVC and NPP showed a fluctuating increasing trend from 2000 to 2022, and the increasing rates were 0.058, 6.90%, and 43.3gC.m-2 per decade respectively. During this period, the number of light, moderate and severe drought days showed a decreasing trend, but the number of extreme drought days tended to increase. (2) The negative correlation of NDVI, FVC and NPP and drought increased from moderate to extreme drought, and from light to extreme drought, the negative correlation between NDVI and FVC and drought decreased, while that of NPP increased. (3) Light and moderate droughts had obvious negative impact on Chinese fir and broad-leaved forest, whereas severe and extreme droughts had obvious negative effect on eucalyptus and bamboo forest.

This article explores the benefits of electrochemical oxidation in pulsed mode, using potential, current, and power pulses. While potential and current pulse electrochemical technology has been previously studied for wastewater treatment, no study has included power pulses until now. The objective of this work is to highlight the advantages of power pulses by applying this pulse type to the electrochemical oxidation of a probe molecule, alachlor. For this aim, the influence of operating parameters and the comparison of the different pulse modes were investigated and compared to the results obtained with the electrochemical oxidation of alachlor in continuous mode. The study shows that the best results were obtained with the power pulse electrochemical oxidation with 100% alachlor degradation after 180 min and a mineralisation yield of 38.3% after 240 min. These results were better than those reported in the literature for treatments with continuous current input using platinum electrodes. This new technique could be an effective and efficient way to treat contaminated water and reduce the pressure on freshwater reserves.

Reactive brilliant red X-3B (RBRX-3B) wastewater is difficult to decolourise, not readily biodegradable, and large in quantity. Therefore, the efficient removal of RBRX-3B is crucial. In this paper, a green and efficient electrochemical-electro-Fenton system with Fe₃O₄-modified carbon felt bag cathode (ECEF-Fe₃O₄) was set up to degrade RBRX-3B wastewater. Experiments confirmed that the removal of RBRX-3B by ·OH or H₂O₂ is quite low, and RBRX-3B can be completely oxidised and degraded directly on the anode. Long-cycle experimental data further shows that the degradation efficiency of RBRX-3B on the anode is 100% at 70 min at the reaction rate constants (k) of 0.071 min^-1 in ECEF-Fe₃O₄ while that of RBRX-3B on the cathode is only 16.8 ± 0.9%. The generation of ·OH is mainly catalysed through the internal cycling of Fe³⁺/Fe²⁺ within Fe₃O₄ on the cathode, and the generation and annihilation of ·OH on the cathode enhance the oxidation efficiency of the anode, achieving the green and effective removal of RBRX-3B by the anode in ECEF-Fe₃O₄.

The inevitable UV aging of microplastics (MPs) is one of the key factors affecting their interaction with antibiotics. In this study, polyethylene (PE) and polystyrene (PS) MPs were aged with UV irradiation. The adsorption isotherms and kinetics of ciprofloxacin (CIP) to virgin and aged MPs were investigated through various models, and the effects of pH on the adsorption amount were explored. Characterization revealed that the surfaces of aged MPs became rougher, and the hydrophilicity increased. These aged MPs were still in the early stage of aging on the basis of their carbonyl index (CI) (<0.2) and O/C (<0.04) values. The adsorption isotherms indicated that the adsorption mechanism of aged PE was different from that of virgin PE. Compared with virgin PE, the adsorption amount of aged PE increased by 87.80-95.45%, and the adsorption rate decreased by 65.52-80.74%. However, aging did not significantly affect the equilibrium adsorption amount or adsorption rate of aged PS. The external diffusion rate (K_ext) (about 2.29-0.36 h^-1) was almost 30 times greater than the internal diffusion rate (K_int) in the film-pore mass transfer (FPMT) model, indicating that CIP adsorption rate was dominated by external diffusion. A hydrated functional zone is thought to form around aged MPs, thus changing the adsorption mechanism and adsorption amount of aged PE. Therefore, more attention should be given to alterations in the hydrated functional zone in the early stage of MPs aging.

Cephalexin (CPX) is an antibiotic widely used to treat many infections. CPX has become an emerging pollutant present in wastewater. On the other hand, it is well known that organic compounds can be adsorbed over metal surfaces when the metal is in active state such as when it is rusting. This work proposes an alternative for the elimination of CPX from wastewater, applying electrochemical principles using a conventional and cheap substrate, aluminium. The first part consisted of obtaining the active states of aluminium electrodes carrying out voltametric curves at different pH (4, 7 and 9) to find the particular condition of interaction between CPX and metal surface. The potential was used in the potentiostatic tests to set the activation potential of metal at different times. After the treatment, electrolyte solutions were analysed using UV-vis spectra, and the aluminium surfaces were studied by optical micrographs and X-ray diffraction. In addition, aluminium-CPX interactions were corroborated by quantum-chemical calculations and adsorption isotherms. All results indicate that it was possible for the CPX removal at basic pH conditions, where the molecule adsorption on the aluminium substrate occurs due to a strong electrostatic interaction.

Biochar is a promising material for wastewater treatment. This study assessed multi-module biochar filters (MmBFs) as onsite wastewater treatment systems (OWTSs), comprising movable modules filled with biochar to remove chemical oxygen demand (COD), nitrogen, phosphorus, and Escherichia coli (E. coli) in wastewater. The MmBF treats wastewater sequentially through six modules: three aerobic modules (M1-M3) for organic matter oxidation and nitrification, two anoxic modules (M4-M5) for denitrification, and an additional module (M6) for the removal of faecal bacteria using biochar and bark. The experiments ran for 381 days using three identical MmBF pilots with two distinct sampling periods, conducted under conditions relevant to OWTSs using municipal wastewater as influent. Water samples were taken from the influent, final effluent, and effluent of each module to evaluate the removal efficiency of organic matter, nitrogen, phosphorus, and E. coli. During the second sampling period, the results showed a 95 ± 2.1% removal of COD, along with a substantial removal of total inorganic nitrogen (71 ± 6.6%). However, phosphate removal was limited (3.4 ± 30.4%). E. coli removal decreased from 2.63 ± 0.93 log₁₀ removal in the first sampling period to 1.8 ± 0.73 log₁₀ removal in the second sampling period. In summary, the MmBFs showed promising potential in treating organic matter, nitrogen, and E. coli, making it an alternative option for OWTS. However, further exploration is needed to assess long-term performance, micropollutant removal, and biological activities. Design enhancements, especially for phosphorus removal are necessary.

In recent years, plant extracts have attracted increased interest as green alternatives to conventional anti-scaling. This is because they contain a wide range of bioactive compounds with high performance against inorganic scale. Additionally, they are biodegradable and pose minimal risks to human health and ecosystems. The present study aimed to assess the protection offered by the Rosmarinus officinalis L. leaf extract for industrial plant surfaces against the CaCO₃ scale. Before assessing the anti-scaling performance of the Rosmarinus extract, phytochemical characterisation was performed by quantitative assays and HPLC-DAD analysis. Subsequently, the inhibition potential of the extract was studied using the conductivity and LCEE tests at 25°C and TH = 40°f. In addition, SEM and XRD analysis were used to assess the effect of the extract on scale morphology and crystalline phases. Finally, DFT calculations and Monte Carlo simulation were carried out to enhance knowledge of the interaction between inhibitor molecules and CaCO₃(104) and (110) surfaces and optimise [extract molecule - Ca]²⁺ complexes. Phytochemical analysis revealed the presence of several phenolic compounds (rosmarinic acid, vanillic acid, cinnamic acid, rutin, kaempferol, trans chalcone and quercetin). Further LCEE studies demonstrated the promising anti-scaling activity of the extract at an effective concentration of 54 mg/L. SEM micrographs and XRD diffractograms revealed a significant change in the morphology and phases of precipitated CaCO₃ scales upon the addition of the inhibitor. In addition, the computational approach strongly supported the experimental results. These results underlined the Rosmarinus extract's potential as a valuable green and sustainable scaling inhibitor source.

This study presents an innovative process for recovering sulphur from hazardous waste incineration flue gases, designed to produce a marketable sodium bisulphite solution while ensuring complete SO₂ removal. This new process is characterized by a double absorption strategy at two different pH levels. The first step, at an acidic pH, generates the desired bisulphite solution, while the second step, at a basic pH, produces the sulphite solution for recycling into the first step and ensures total SO₂ removal. The process's performance and feasibility were evaluated on a laboratory scale using a batch reactor with synthetic gas. The parametric study focused on the initial sulphite concentration in the absorption solution and the reactor temperature. A removal efficiency exceeding 95% was achieved across all initial sulphite concentrations and temperature ranges, when the pH was maintained above 6. At pH 5, where bisulphites are the predominant sulphur species, the removal efficiency remained substantial at approximately 70%. The oxidation of sulphites/bisulphites by oxygen in the flue gases was minimal, with less than 5% conversion to sulphate. Additionally, pH-controlled experiments were conducted to optimize plant start-up procedures. For the basic reactor, starting with water and adjusting the pH to 8 during SO₂ absorption effectively minimized sodium hydroxide consumption. In contrast, for the acidic reactor at pH 5, initiating the process with a concentrated sulphite solution resulted in more stable absorption rates. These findings underscore the process's potential for efficient sulphur recovery and highlight the importance of pH management in optimizing operational stability and chemical consumption.

This study evaluated the reliability of the emulsified liquid membrane (ELM) extraction technique for recovering and separating metals, focusing on Nickel (Ni(II)) and Samarium (Sm(III)), both used in electrochemical devices. Key contributions include determining optimal conditions for creating a stable water-in-oil (W/O) emulsion. The optimal conditions were found to be a 5-minute emulsification time, 4 wt.% Span 80 surfactant concentration, a 1.6 volume ratio of the internal phase to the organic phase, 1 M H2SO4 concentration for the internal phase, a 40/160 volume ratio of the emulsion to the external phase, and kerosene as the diluent. Factors affecting the separation of Ni(II) and Sm(III) included the concentrations of the internal aqueous phase, surfactant, and extractant. Under these conditions, an equimolar mixture of Ni(II) and Sm(III) was extracted within 15 min. The study emphasized the importance of phase volume ratio and surfactant concentration for emulsion stability and extraction efficiency. The response surface method (RSM) and Box-Behnken design were used to optimize influential factors, with a modified quadratic model predicting extraction yields of 83.81% for Sm(III) and 15% for Ni(II). The study demonstrates that effective separation of Ni(II) and Sm(III) ions is achievable using this technique, providing valuable insights into efficient and selective metal ion extraction, contributing to the broader field of metal recovery and recycling technologies.

High-salinity wastewater, owing to its intricate composition and challenging treatment requirements, poses a significant hurdle in water environmental governance. In this study, low-temperature evaporation technology is used to tackle wastewater containing the volatile organic compound such as N,N-dimethylacetamide (DMAC). Utilisation of comprehensive approaches involving experimental testing, mathematical modelling, and Aspen Plus software simulations, The influence of DMAC on evaporation efficiency is researched through the following factors which encompassing its effects on boiling point elevation, partial molar activation energy, and the formation of by-products. Additionally, the comparation of the impact of temperature, ionic strength, intermolecular interactions on the evaporation rate and the concentration of the volatile component DMAC in the condensate is also conducted in this study. After conducting a multiple linear regression analysis of evaporation efficiency using the Statistical Product and Service Solutions (SPSS) tool, it was discovered that temperature serves as the primary determinant influencing the evaporation rate. Additionally, ionic strength impacts solution viscosity, intermolecular interactions, and saturated vapour pressure by altering the intermolecular forces, thereby indirectly influencing both the evaporation rate and the quality of condensate water. The comparative analysis of single-effect and double-effect evaporation indicates that the optimal operating condition for double-effect evaporation yields an evaporation rate of 70%, with a remarkable 88% reduction in steam consumption compared to single one. Based on heat and mass balance principles, the mathematical model for double-effect evaporation is established to offer crucial data support for practical industrial applications.