查看更多>>摘要：The degree of stability and maturity of the organic matter are fundamental features of the chemical characterization of compost. These characteristics are related to the extensive formation of aromatic structures and of oxygen-containing functional groups. The increase of the amount of these chemical moieties can be assessed by different analytical methodologies, based on thermal, spectrophotometric, and electrochemical techniques. In order to compare the ability of the most used methodologies to differentiate compost at different composting stages, results from the direct characterization of solid samples and their extracts are reported. A total of 108 parameters from the characterization of a compost at four composting stages were treated by a ComDim analysis. The relevance of the analytical techniques for monitoring composting was established by considering the absolute value of the loadings and that results vary in a single way along the process.
查看更多>>摘要：Today, oil and gas trunklines from production to consumption have become one of the challenges for governments. Due to the need to install energy-intensive equipment such as compressors, turbines and pumps along the trunkline route, a systematic study of the environmental impact of this trunkline has received less attention from researchers. However, from a social and environmental point of view, the benefits of this transfer in the face of its environmental effects have always been criticized by indigenous groups and environmentalists in the region. The purpose of this study is to evaluate and systematically analyze the environmental effects of the natural gas trunkline process in part of the sixth national gas trunkline of Iran, which is done for export to neighboring countries. The research method is life cycle assessment. After defining the goal and scope, in the second step, the flow data of the inlet and outlet gas, the amount of gas rivet, the amount of turbine emissions, the amount of electricity consumption, the amount of gas consumed and the amount of black powder entering the collection station and energy consumption calculations were performed. In the third step, the environmental effects of the system were examined from two perspectives: (1) the effects that can lead to environmental problems and (2) the damage that can be done to human health, ecosystem, and resource. These analyses were reviewed at two general levels of the system and each station and equipment. The results showed that the total annual carbon dioxide emissions of this pipeline in Ahvaz station emit 70,149 kg CO2 eq per day, which is the highest amount of emissions among all stations. This is equivalent to 30,499 liters of car fuel per year. On the other hand, Bidboland station emits 7443 kg CO2 eq per day of carbon dioxide, which is the lowest emission among all stations. Due to the environmental effect of water consumption, Ahvaz station with 39 m3 per day has the highest amount among stations and Bidboland station with 6 m~3 per day has the lowest consumption.
查看更多>>摘要：To address the internal concentration polarization (ICP) effect and membrane fouling problems of forward osmosis technology in pressure retarded osmosis (PRO) mode, another highly selective polyamide (PA) layer was introduced on the other side of the single-skinned forward osmosis (FO) membrane. Recently, a new symmetrical nanofiber support layer has shown excellent performance. For better proof, the nanofiber support layer and the phase inversion support layer were prepared separately in this study, respectively, and two double-skinned FO membranes were obtained via interfacial polymerization. By comparing various surface physicochemical properties of the nanofiber support layer and the phase inversion support layer, it can be seen that the double-skinned PA layer formed on the surface of the nanofiber support layer had better performance. The nanofiber double-skinned FO membrane showed water flux of 19.99 LMH when using 2 M NaCl and DI water as the draw and feed solution, much higher than that of the phase inversion double-skinned FO membrane. Furthermore, the anti-fouling performance of the nanofiber double-skinned FO membrane was also better than that of the phase inversion double-skinned FO membrane. This study pointed out a new direction for a double-skinned FO membrane with high permeability selectivity and provided a promising method for anti-membrane fouling.
查看更多>>摘要：The Cr recovery from the Cr-containing tailings of vanadium extraction always generates large amounts of hazardous wastewater sludge and solid waste. This work proposed an eco-friendly Cr recovery method based on low-dosage soda roasting for a new kind of Cr-containing tailing, the Mg-based tailing. The low dosage of soda ensures the targeted conversion of Cr-bearing phases in the Mg-based tailing during roasting and minimizes the soda roasting of accompanying phases other than Cr-bearing phases, leading to the minimization of waste discharge. In the optimal condition of low-dosage soda roasting-water leaching, the Cr extraction efficiency is as high as 93.25 %;; from the leach liquor, the Cr2O3 product is obtained by Na2S reduction, precipitation, and calcination with total Cr recovery of 92.93 %. For Cr extraction, the soda dosage has been reduced by 20 % while the production rates of hazardous sludge, leach residue, and CO2 have been reduced by 30 %, 18 %, and 20 %, respectively. This work exemplifies the control of targeted phase conversion to minimize hazardous wastes, which provides a novel strategy for eco-friendly resource utilization of hazardous tailings.
查看更多>>摘要：Recycling lixiviant from sodium silicate solution is a key to the cleaner utilization of aluminosilicate solid wastes such as coal fly ash and coal gangue via ferric oxide assisted roasting - alkali leaching silica process. This work focuses on seeded precipitation of higher-modulus sodium silicate solution to obtain recyclable spent solution with lower-modulus. The results show that adding silica hydrate seeds can induce the decomposition of sodium silicate solution to obtain amorphous silicate hydrate and low-modulus spent solution. The SiO2 precipitation yield, precipitation rate and the spent solution modulus can respectively reach up to 108.26 g/L, 72.17 % and 0.86, under the appropriate conditions: initial modulus 3.09, total Na2O concentration 50 g/L, seed amount 350 g/L-liquor, temperature 50 °C, and duration 6 h. Meanwhile, the average particle size of precipitation product is ～ 56.20 μm. Moreover, the structural evolution of silicates during the precipitation implies that silica hydrate mainly precipitates from high-polymerized silicates. The precipitation product was further characterized as opal-A by XRD, chemical composition, TG-DSC and FT-IR analyses. This work may be beneficial either to improving the ferric oxide assisted roasting - alkali leaching silica process for treating aluminosilicate solid wastes or to developing a new technology for preparing opaline silica hydrate.
查看更多>>摘要：The gasification fine slag black water (GFSBW) is a kind of slurry including fine gasification fine slag particles produced in the coal gasification process and ineffective disposal process causes environmental pollution and resources waste. The aim of this study is to recover combustible matters, high silica-aluminum minerals and water resources via reprocessing GFSBW by innovative separation process of "flotation-agitator-ceramic membrane vacuum (CMV) dewatering". The physicochemical properties of samples are characterized and at least 6 kinds of carbon-ash occurrence modes of gasification fine slag were found. The flotation process could be a useful method to separate residual carbon and tailing ash. The dewatering processes of flotation slurries are then achieved by the ceramic membrane vacuum filtration, followed by dewatering combustible matters, high silica-aluminum minerals and industrial-water-grade filtrate will be recovered. It is worth noting that the components separation of GFS eliminates their synergistic water holding effect and the average dewatering effect after flotation is improved by 11.67%, and the fixed carbon content of combustible matters is elevated from 22.74% to 44.64%, while the tailing ash including high silica-aluminum minerals is purified to 97.25%. A novel flotation-agitator-ceramic membrane vacuum (CMV) dewatering flowsheet is developed, and useful resources could be recovered to realize waste comprehensive utilization. The proposed GFSBW processing flowsheet could bring 9.82 million US$ per year which is benefit.
查看更多>>摘要：A multi-stage pressurized vertical electro-osmotic dewatering (MS-PVEOD) were designed to break through the dewaterability limit of pressurized vertical electro-osmotic dewatering (PVEOD) process and reduce energy consumption (EC). The effects of mechanical pressure and voltage on sludge moisture content (MC) are studied. The sludge MC can be reduced to 44.6 % and 54.7 % respectively after MS-PVEOD (0-2-3.5 MPa) and PVEOD (2-2-2 MPa) process dewatering under 40 V, and the total EC of the former is 33 % lower than that of the latter. The sludge morphology, electric current, protein (PN) and polysaccharide (PS) content and fluorescence spectrum of extracellular polymeric substances (EPS) were analyzed. The PN/PS of the sludge treated by the MS-PVEOD process is 16.3 % higher than that of the PVEOD process, and 20.0 % higher than that of the raw sludge (RS). The three-dimensional fluorescence spectrum (3D-EEM) showed that the fluorescence of hydrophilic fulvic acid and humus decreased more than that of hydrophobic tryptophan protein and tyrosine protein. The present work may be helpful to understand the dewatering mechanism of MS-PVEOD and provides some useful technical guidance for the industrial application of efficient deep dewatering of sludge.
查看更多>>摘要：Natural gas pipeline leaks can cause serious hazards to natural gas transportation and pose considerable risks to the environment and the safety of residents. Therefore, feature extraction of pipeline signals is crucial in natural gas pipeline leak detection. However, the quality of feature extraction directly affects the effectiveness of pipeline leak detection. Therefore, this paper proposes a pipeline leakage feature extraction method based on variable mode decomposition (VMD) and local linear embedding (LLE). First, the pipeline signal is decomposed into several modal components by VMD;; then, the dispersion entropy is used to select the feature modes. Secondly, the time-frequency domain features of different components are extracted to construct a high-dimensional feature matrix, which LLE reduces to obtain the classified low-dimensional feature vectors. Finally, the extracted feature vectors are used to train and test the support vector machine (SVM). By analyzing the experimental results, it can be seen that the proposed method can classify pipeline signals with an accuracy of up to 95%, which effectively solves the problem of false alarms and missed alarms in pipeline leakage detection.
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