查看更多>>摘要：Nitrate (NO3~-) pollution of water bodies is a serious environmental problem worldwide. One of the major concerns about NO3~- contamination is the lack of cost-effective solutions for its removal from potential drinking water resources. Current technologies, such as ion exchange, reverse osmosis and electrodialysis, produce a reject with high NO3~- concentration. Catalytic reduction is an emerging technology, capable of transforming NO3" into harmless N2. A critical issue is to achieve almost complete selectivity to this last species so that the final concentrations of NO2~- and NH4~+ can fit the stringent allowed limits. Numerous studies have been carried out evaluating the activity and N2 selectivity of bimetallic catalysts. Catalyst deactivation by surface fouling, irreversible oxidation of the metal promoter, metal leaching and aggregation of metallic particles remain a major challenge for full-scale implementation of catalytic nitrate reduction. Therefore, it is necessary to develop highly stable catalyst and/or effective solutions for catalyst regeneration. The existing literature on this respect is reviewed hereby.
查看更多>>摘要：Conventional contact membrane distillation technology has some problems, such as membrane fouling and wetting, resulting in short membrane life, low permeate flux, and instability, which limit its industrial application. Here, a non-contact membrane distillation method is proposed for radioactive wastewater treatment. The effects of hot-side inlet temperature, hot-side flow rate, sweeping gas temperature, and cold-side flow rate on permeate flux are examined. The purification ability of this method for strontium ion in simulated radioactive wastewater and actual radioactive wastewater from uranium-containing hydrometallurgical purification plant was investigated. Under the optimized conditions, the permeate flux of non-contact membrane distillation unit reaches 24.87 kg/(m~2 ·h), the rejection rate of Sr~(2+) in simulated radioactive wastewater is more than 99.99%, and the decontamination factor can reach more than 4.5 × 10~6. The total α and β activity concentrations in the radioactive wastewater are 21279.7 Bq/L and 17811.9 Bq/L, respectively, while the actual α and β activity concentrations of the distillate produced by the membrane distillation device are 0.205 Bq/L and 0.877 Bq/L, respectively. Overall, the proposed method has the advantages of long membrane sendce life, high and stable permeate flux, which can facilitate its large-scale industrial application in volume reduction and deep purification of radioactive wastewater.
查看更多>>摘要：Single-pass tangential flow filtration (SPTFF) is used in biopharmaceutical manufacturing to reduce volumes and concentrate products. The staging of multiple membrane cassettes makes it possible to achieve high concentration factors in one pass, but at the same time increases the system's complexity. This work aims to provide comprehensive understanding of SPTFF at both membrane cassette level and at equipment level by evaluating the impact of different operating conditions and different filter designs on the filtration performance. An experimentally validated computational fluid dynamics (CFD) model of a commercial ultrafiltration membrane cassette was developed and first used to study the impact of operating conditions on the volumetric concentration factor (VCF). The results show that both the feed flux and the retentate pressure have a substantial impact on the VCF. At low pressures (0.0-0.4 bar) a VCF of 1.2-2.9 is achieved for feed fluxes of 137-394 L m~(-2) h~(-1), while at high pressures (0.6-1.0 bar) a VCF of up to 10.5 is achieved. The model was subsequently applied to study concentration-dependent effects and the spatial distribution of relevant physical properties. The simulation results help select suitable operating conditions and evaluate the cassette design with respect to product accumulation. Finally, a systematic comparison of different multi-stage filter designs was performed. The results show clear advantages of mixed filter designs over serial filter designs in terms of TMP and VCF, and serve as a guidance to select a suitable filter design for given concentration targets and pressure limits. An advantage of the presented modelling approach is its applicability to the evaluation of other membrane systems with different geometric dimensions and different membrane properties.
查看更多>>摘要：Improving the permeability and selectivity of the thin-film composite (TFC) nanofiltration membranes is the key to energy conservation and emission reduction in water treatment. Nowadays, the construction of interlayer is an effective approach to improve the performance of TFC nanofiltration membranes, and the construction of interlayer is a much more effective approach, which can directly form an interlayer in the interfacial polymerization (IP) process. However, there are few studies on the construction of nanoparticles based interlayer, due to the stability problem of nanomaterial dispersion system. Herein, Noria and 2, 2'-benzidinedisulfbnic acid (BDSA) were used to prepare a novel kind of stable nanoparticles system, which can be formed as Noria-BDSA nanoparticles interlayer for follow-up IP process. The TFC membrane with Noria-BDSA nanoparticles interlayer had a thin and crumpled polyamide layer, which can reduce the hydraulic resistance and improve the effective area during the separation process. Hence, the permeability of this TFC membrane (24.01 L m~(-2)h~(-1) bar~(-1)) was about 3.5 times that of the conventional TFC membrane. Furthermore, the polyamide layer of this TFC membrane had a higher crosslinking degree, which made it have a higher rejection than conventional one.
查看更多>>摘要：The efficacy of an adsorbent agnostic machine-learning surrogate model for rapid design and optimization of a Skarstrom cycle vacuum swing adsorption (VSA) process is experimentally validated. The surrogate model is trained to predict the process performance using adsorbent features that include hypothetical Langmuir adsorption isotherm parameters, particle density, porosity and bed voidage, and process variables such as pressure, step duration and feed velocity. The training data was generated from a detailed process model for 20,000 unique combinations of the training variables. The model shows high accuracy of R_(adj)~2 >0.99 for predicting key performance parameters such as product purity, recovery and productivity. The ability of this surrogate to predict the experimental performance for the purification of O2 from air on two adsorbents, namely 13X and LiX zeolites, was studied. Two separate multi-objective optimization studies, to maximize purity and recovery, and to maximize productivity and purity were performed. For these optimization studies, the volumetrically measured isotherms of N2 and O2 were used as inputs to the surrogate model. Note that these isotherms were not a part of the dataset used to train the model. Nine points were chosen from the Parteo curves and the corresponding decision variables were used as set-points in a two-column lab-scale rig. The average difference between the calculated and experimentally measured purity, recovery and productivity was 3%, 5% and 9%, respectively. This study provides the necessary confidence to use surrogate-based process models for adsorbent screening and adsorption process optimization.
查看更多>>摘要：Solids formation can substantially reduce the energy penalty for ammonia solvent regeneration in carbon capture and storage (CCS), but has been demonstrated in the literature to be difficult to control. This study examines the use of hollow fibre membrane contactors, as this indirect contact mediated between liquid and gas phases in this geometry could improve the regulation of solids formation. Under conditions comparable to existing literature, NH4HCO3 was evidenced to primarily crystallise in the gas-phase (lumen-side of the membrane) due to the high vapour pressure of ammonia, which promotes gaseous transmission from the solvent. Investigation of solvent reactivity demonstrated how equilibria dependent reactions controlled the onset of NH4HCO3 nucleation in the solvent, and limited 'slip' through transfomation of ammonia into its protonated form which occurs prior to the phase change. Crystallisation in the solvent was also dependent upon ammonia concentration, where sufficient supersaturation must develop to overcome the activation energy for nucleation. However, this has to be complemented with a reduction in solvent temperature to offset vapour pressure and limit the risk of gas-phase crystallisation. While changes to the solvent chemistry were sufficient to shift from gas-phase to liquid phase crystallisation, wetting was observed immediately after nucleation in the solvent. This was explained by a local region of supersaturation within the coarse membrane pores that promoted a high nucleation rate, altering the material contact angle of the membrane sufficient for solvent to breakthrough into the gas phase. Adoption of a narrower pore size membrane was shown to dissipate wetting after crystallisation in the solvent, illustrating membrane contactors as a stable platform for the sustained separation of CO2 coupled with its simultaneous transformation into a solid. Through resolving previous challenges experienced with solids formation in multiple reactor configurations, the cost benefit of using ammonia as a solvent can be realised, which is critical to enabling economically viable CCS for the transition to net zero, and can be exploited within hollow fibre membrane contactors, eliciting considerable process intensification over existing reactor designs for CCS.
查看更多>>摘要：Membrane distillation crystallization (MDC) is a promising technique for treatment of inland desalination brines due to its ability to recover clean water and solid salts. The MDC system developed in this study used a six-tray cascading crystallizer with extended mesh surfaces to provide nucleation sites and support for crystal growth. Sodium chloride (NaCl), potassium chloride (KC1), and sodium nitrate (NaNO3) brines were used to investigate clean water and solid salt recovery using MDC, as well as brine volume reduction. When compared to MD alone, MDC achieved higher water and solid salt recovery under the same operating conditions, resulting in greater reductions in brine volume, while retaining >99.8% rejection for all three salt species. Solid salts were recovered from all three feed solutions, with NaNO3 feed solution, which has the strongest temperature-solubility relationship, having the highest yield (126.55 ± 6.65 g).
查看更多>>摘要：In this study, a novel high-efficient approach of directly extracting lithium from the Da Qaidam artificial raw brine (the main components: Li~+ 0.10?g · L~(-1), Na~+ 82.34?g · L~(-1)) by LiFePO4/FePO4 material through the chemical redox method was proposed. The extraction process demonstrated a fast reaction speed and expected lithium adsorption capacity which reached 9.13?mg·g~(-1), and the whole process could be online monitored by measuring the solution;;s redox potential and pH value. Besides, the adsorption process exhibited excellent ion selectivity while the separation coefficient of lithium towards sodium, potassium, and magnesium reached 8704, 2460, and 6864 respectively. This extraction method features high efficiency, facile and continuous operation, and provides an alternative pathway to directly extract lithium from raw brines.
查看更多>>摘要：The interface coupling of crystalline catalytic materials exhibits unique functions in removing pollutants and purifying water resources; however, little attention has been paid to the effect of different crystal surface coupling on photogenerated charge separation. In this study, different coupling facets of α-Fe2O3 were constructed on cyclized carbon nitride (ACN) by impregnation hydrothermal method, and the coupling mechanism of α-Fe2O3 crystal facets on ACN was explained. The α-Fe2O3 nanosheets can be assembled parallelly or vertically on the surface of ACN due to the surface energy of α-Fe2O3 crystal facets and the different surface charges of ACN. The Z-scheme heterojunction formed by different interface coupling between α-Fe2O3 and ACN improved the separation efficiencies of photogenerated carriers. The photodegradation of organic pollutants and antibiotics showed that the photoactivity of Fe110/ACN+ was much higher than that of ACN, ACN+ and Fe001/ACN. The maximum removal rate of oxytetracycline by Fe110/ACN+ composites was 88.6%, and it had excellent adsorption and catalytic effect on organic dye Congo red within 120 min. Overall, the work may provide a new perspective for designing structures of unique crystal surface coupling and constructing heterojunctions with high catalytic performance.
查看更多>>摘要：Dimetridazole (DMZ) is widely used as a veterinary antibiotic, but it is recalcitrant in the water environment. The residual of DMZ has raised widespread concern because of its harmful effects on human health and environmental safety. This work aimed to investigate the degradation of DMZ and the corresponding formation of halonitromethanes (HNMs) during the ultraviolet (UV)/chlorine process. The UV/chlorine process presented an excellent performance in DMZ degradation. The observed degradation rate constant of DMZ by UV/chlorine was 1.4 × 10~(-1) min~(-1). The hydroxyl radicals (· OH) and chlorine radicals (- Cl) were the predominant reactive species for DMZ degradation, and corresponding contributions were 79.8% and 13.7%, respectively. With the increase of free chlorine dosage, the degradation efficiency of DMZ firstly increased and then slightly decreased, while the formation of HNMs increased after 40 min UV/chlorine treatment. The higher degradation efficiency of DMZ was observed at acid circumstances, while higher HNMs formation was found at alkaline conditions due to base-catalyzed hydrolysis and less degradation of HNMs. The presences of Cl~-, Br~-, HCO3~- and humic acid (HA) inhabited the degradation of DMZ. Furthermore, the possible degradation pathways of DMZ were proposed based on five intermediate products identified by UPLC/MS. Overall, the UV/chlorine was an efficient method for DMZ removal, but the formation of HNMs from DMZ should be evaluated before using UV/chlorine.
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