查看更多>>摘要：Toxic organic dyes are a serious threat to the global environment, and membranes with catalytic properties show great promise as a green water treatment method for removing these pollutants. Herein, Ti3C2/W_(18)O_(49) photo-catalytic membranes were constructed by vacuum filtrating Ti3C2 and W_(18)O_(49) to form a hybrid layer on a mixed cellulose ester (MCE) support. The efficient separation of dyes was attributed to the negative charge and abundant -OH groups of Ti3C2/W_(18)O_(49), which can capture cationic dyes by electrostatic adsorption and form hydrogen bonds with the amino groups of dye molecules. Moreover, the Ti3C2/W_(18)O_(49) membrane exhibited excellent photocatalytic performance and a dye-contaminated membrane was regenerated under visible light in 120 min. The two component materials complement each other, with the W_(18)O_(49) providing adsorption sites and photocatalytic ability and the Ti3C2 serving as an electron trap and improving charge separation. Photoinduced electrons in the conduction band of W_(18)O_(49) are transferred to Ti3C2 to form ~·O_2~- while holes remain in the valence band of W_(18)O_(49) to generate 'OH, and h~+. ~·O_2~- and 'OH are mainly responsible for the degradation of dyes. Therefore, this efficient and easily prepared membrane shows practical potential as a next-generation method for dye removal from water.
查看更多>>摘要：Air purification can effectively capture particulate matter and reduce the health risk from indoor air pollution. However, it remains a challenge to fabricate filtration materials with high filtration efficiency, low filtration resistance, and large dust holding capacity at the same time. Herein, we report Needle-punched Electret Air Filters (NEAFs) not only exhibiting the abovementioned performance, but also owning superior charge and filtration stability. By employing corona charging and MgSt charge enhancing additives, NEAFs exhibited high filtration efficiency (99.2%) and ultralow filtration resistance (13.93 Pa). Importantly, NEAFs only had 0.6% decline in filtration efficiency after heat treatment, which was much better than commercial meltblown materials. In addition, the needle-punching technique generated a unique 3D fluffy structure, resulting in a large dust holding capacity of 23.6 g m~(-2). Our design of NEAFs may provide new guidelines for next-generation high-performance air filiation materials.
查看更多>>摘要：Metal nanoparticles frequently exhibit good selective extraction ability for Hg(II) in water environment. Here, a kind of Ag-coordination aramid nanofiber-silver nanoparticle composite beads (ANF/Ag) was facilely fabricated using aramid nanofiber (ANF) as the motifs through Ag(I) coordinated self-assembly process. The formation mechanism of ANF/Ag nanoparticle composite beads was established, and the adsorption performances were performed using batch and dynamic experiments, respectively. Ag firstly as promoter coordinated self-assembly of ANF/Ag composite beads, and that can play a role of active sites. ANF/Ag composite showing high adsorption capacities and excellent selectivity towards Hg(II). The adsorption process for Hg(II) followed pseudo-second-order model well, while the dynamic adsorption could be described by the Yoon-Nelson model. Furthermore, adsorption process was a monolayer and chemical adsorption verified by isotherm adsorption. Meanwhile, the maximum adsorption amount of ANF/Ag for Hg(II) was achieved 370.4 mg g~(_1). More importantly, ANF/Ag displays remarkable regeneration ability after 5-cycle five cycles of adsorption-desorption. Therefore, this project not only presents an ANF/Ag composite for Hg (II) removal field in environmental pollutions control, but also opens a new design field of ANF material.
查看更多>>摘要：Safe and effective coagulants are necessary for surface water treatment. The polyaluminum-titanium chloride (PATC) composite coagulant has promise but its application is limited due to the lack of fundamental theoretical research. We prepared a series of novel PATCs and investigated the effects of the interaction between Al (III) and Ti (IV) on the chemical species distribution, physicochemical properties and coagulation efficiencies. The Al-O-Ti bonds observed in the PATC infrared spectra were predicted by density functional theory computation to appear in 4-atom rings in the structure. The differences in Al species distribution of PATC and PAC illustrated that the introduction of Ti retarded the hydrolysis of monomeric Al species (Al_a) and medium polymerized Al species (Al_b) to colloidal Al species (Al_c) at low B levels, but the transformation was promoted at high basicities (B). PATCs exhibited higher charge densities and larger molecular weights than PAC at the same B levels, which contributed to their excellent coagulation efficiencies. PATC with low B values but high Al/Ti molar ratios mainly provided charge neutralization in removal of humic acid kaolin, while the dominant coagulation mechanism converted from charge neutralization to sweeping and bridging effects at high B values or low Al/Ti molar ratios.
查看更多>>摘要：The separation of dimethyl carbonate (DMC)/methanol/water azeotropic mixtures has been a hot topic in the study of DMC synthesis process. In this work, the efficient organic solvent methyl salicylate, ionic liquids (ELs) 1-butyl-3-methylimidazolium chloride ([BMIM] [Cl]), or l-butyl73-methylimidazolium bis(trifluoromethylsulfonyl) imide ([BMIM][NTf2]) was employed to break azeotropic mixtures. Interaction mechanisms between DMC/ methanol/water and entrainers were revealed by sigma-profile. Energy and economic comparison of two alternative separation sequences including pre-separation integration with extractive-heterogeneous distillation and direct extractive distillation processes were investigated. The average relative deviations (ARD) were used to check the reliability of the NRTL model. The effect of high viscosity fluid on the mass transfer was analyzed from the perspective of the overall efficiency of column. For [BMIM] [Cl], the separation mechanism is the formation of H-bond between [BMIM] [Cl] and methanol/water. Direct extractive distillation process is superior to pre-separation integration with extractive-heterogeneous distillation process in terms of steam consumption, capital cost, mass transfer efficiency and total annual cost (TAC), and [BMIM] [Cl]-based direct extractive distillation process is the best. This work provides a green and efficient separation route for replacing organic solvent-based process.
查看更多>>摘要：Industrial wastewater containing organic ligands and heavy metals is considered a serious public health threat, and its treatment and purification have become challenging tasks. Moreover, the organic-chelated heavy metals formed by common organic ligands and free heavy metals can cause many problems and concerns because of their poor biodegradability, high solubility, and extreme stability. In this study, aluminum-containing ferrihydrite (Fh-Al) adsorbents of different composition molar ratios were prepared and utilized to remove typical EDTA-Cr(III) in an aqueous system, and the associated removal mechanism was examined. The experimental results show that adding Al not only enhances the removal rate of EDTA-Cr(III) by the Fh-Al adsorbent in a wide pH range (pH = 3-9) but also increases the maximum adsorption capacity of EDTA-Cr(III). In addition, the specific surface area of Fh-Al can be increased by adding aluminum with different molar ratios, thus promoting its adsorption performance for EDTA-Cr(III). Furthermore, surface complexation and electrostatic attraction were proposed as possible mechanisms of EDTA-Cr(III) adsorption by Fh-Al. This study shows that Fh-Al-6 adsorbent can adsorb common EDTA-chelated heavy metals (such as EDTA-Pb, EDTA-Cr, EDTA-Cu and EDTA-Cd) in one step, with maximum adsorption capacities of 41.47, 32.33, 16.51 and 31.27 mg/g at pH = 3. The Fh-Al-6 adsorbent can be reused after being regenerated in a 2 g/L Na2SO4 solution. This study provides new expectations for treating wastewater containing organic groups and heavy metals.
查看更多>>摘要：Photocatalysis is highly efficient for the treatment of dyeing wastewater. However, the wastewater still contains a large amount of nano-TiO2 after photocatalysis. In order to reduce the cost of nano-TiO2, different coagulants were used to improve the solid/liquid separation efficiency. At the same time, the reuse of flocs has raised increasing attention after coagulation. In this study, we report on the recycling of flocs for the production of AlCl3 and TiO2 formed flocs (AT1) and Al_(13) and TiO2 formed flocs (AT2) through a simple calcination process. Results indicated the flocs formation processes under different concentration of CO_3~(2-) were Al species distribution and coagulant dosage dependent. Without HA molecules, the reaction between Al-based coagulants and CO_3~(2-) are the controlling steps in the coagulation process, and Al_a and Al_b species had different reaction processes. The influence of HA molecules was also studied, and the HA-A1 aggregates which could bridge the TiO2 nanoparticles, and thus induce sweep flocculation. Consequently, highly enhanced aggregation rate, due to the hetero-aggregation between these aggregates and TiO2 was observed. After calcination, the AT2-10 and AT2-20 (CO_3~(2-): 10, 20 mmol/L) with petal-like structures (mesoporous), relatively high specific surface areas, i.e. 83.98 m~2/g and 78.38 m~2/g and high photocatalytic degradation, i.e. 72.79%, 67.78% (compared to nano-TiO2, AT1-10 and ATx-20), were obtained. Additionally, oxygen vacancy (OV) was generated on the surface of the recycled AT2-10 and AT2-20, which display strong photocatalytic performance for the degradation of MO greater than 65%, under ultraviolet (UV) irradiation and without any sacrificial reagents. This study proposes a new perspective on recycling coagulated flocs for practical application in wastewater treatment.
查看更多>>摘要：Here, a novel series of 2D BiO(HCOO)_xI_(1-x) composites were first fabricated with a ultrathin thickness (~2.47 nm). Among them, the optimal BiO(HCOO)_(0.75)I_(0.25) nanosheets exhibited a superior photocatalytic performance with the kinetic constant reaching up to 0.2148 min~(-1), which was 5.9, 97.6 and 27.2 folds higher man that of pristine BiOI, BiOCOOH and BiO(HCOO)_(0.75)I_(0.75)-P nanoplates, respectively. Benefiting from the synergistic effect of ultrathin two-dimensional structure and hybrid composite, the photocatalytic performance was signally improved. Based on the optical and photoelectrochemical characterizations, the fabrication of hybrid composite delivered the optimal balance of visible-light absorption and redox capacity, endowing the photoinduced holes a higher oxidation potential. Meanwhile, the construction of 2D ultrathin structure reduced the migration distance of charge carriers, consequently accelerated those separated rate. This study provides a new insight for designing high active Bi-based photocatalysts, which is hopeful to make a great contribution to aquatic environmental restoration.
查看更多>>摘要：Industrial wastewater containing N,N-Dimethylacetamide (DMA) and acetic acid (HAC) will be produced in the production of DMA by acetic acid method. The binary mixture of HAc and DMA has maximum-boiling azeotropic point, and the relative volatility of HAc and water is small. Therefore, high purity separation cannot be realized by traditional distillation. By analyzing the separation methods of binary mixture, three processes of extractive-pressure swing distillation, azeotropic-pressure swing distillation, and azeotropic-extractive distillation are proposed to separate DMA-HAc-water ternary mixtures. The heat integration enhancement configuration is completed according to the process characteristics. The results show that compared with the conventional processes, the TAC of the three heat integration processes is reduced by more than 25%, and the energy consumption is reduced by more than 40%. The process quality index (PQI), which integrates TAC, energy consumption, environment and thermodynamic efficiency, is proposed and applied to the evaluation of all processes. The results indicate that the heat integrated azeotropic-extractive distillation (HIAED) process shows more significant industrial application potential.
查看更多>>摘要：Positively charged membranes are essential for the removal of heavy metals from wastewater by nanofiltration (NF). A simple fabrication procedure for synthesizing a positively charged membrane with high permeance and high selectivity is needed to make this realistic. This work prepared a positively charged P84 NF membrane by chemical cross-linking of the asymmetric plain P84 membrane using hyperbranched polyethyleneimine (PEI). Instead of using organic solvent and thermal annealing, the cross-linking reaction occurred in mild conditions with a cross-linker concentration of 15 g L~(-1) and a cross-linking time of 20 h at ambient temperature in water. The modified membrane had increased surface hydrophilicity, surface roughness, and a positively charged surface. The resulting membrane had an excellent water flux of 43.2 L m~(-2)h~(-1) at 4 bar. The cross-linked P84 NF membrane showed high rejections of divalent heavy metals PbCl2, Ni(NO3)2, ZnCk, Cu(NO3)2 with rejections of 99.0%, 96.7%, 96.2%, 99.8%, respectively, which outperforms the commercial NF270 membrane tested in the same conditions. Due to the high cross-linking of the active surface layer, the membrane was found to reject positively charged organic dyes almost completely: Victory blue B (VBB, 506.08 g mo1~(-1)), methylene blue (MB, 319.85 g mo1~(-1)), and negatively charged Congo red (CR, 696.66 g mol''1). The convenient fabrication process could accelerate the progress of the positively charged NF membranes in potential applications of removing heavy metals and positively charged dyes from effluents in industries.
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