Electrochemical water softening technology: From fundamental research to practical application.

In recent decades, the environmentally benign electrochemical softening process has been gaining widespread interest as an emerging alternative for water softening. But, in spite of decades of research, the fundamental advances in laboratory involving electrolytic cell design and treatment system development have not led to urgently needed improvements in industrially practicable electrochemical softening technique. In this review, we firstly provide the critical insights into the mechanism of the currently widely used cathode precipitation process and its inherent limitations, which seriously impede its wide implementation in industry. To relieve the above limitations, some cutting-edge electrochemically homogeneous crystallization systems have been developed, the effectiveness of which are also comprehensively summarized. In addition, the pros and cons between cathode precipitation and electrochemically homogeneous crystallization systems are systematically outlined in terms of performance and economic evaluation, potential application area, and electrolytic cell and system complexity. Finally, we discourse upon practical challenges impeding the industrial-scale deployment of electrochemical water softening technique and highlight the integration of strong engineering sense with fundamental research to realize industry-scale deployment. This review will inspire the researchers and engineers to break the bottlenecks in electrochemical water softening technology and harness this technology with the broadened industrial application area.

Robust electrolysis system divided by bipolar electrode and non-conductive membrane for energy-efficient calcium hardness removal.

In this study, an energy-efficient divided bipolar electrolysis system was developed for water softening, where two PTFE membranes were used as the separating materials and a bipolar electrode was employed to enhance the H2O-splitting reactions. As compared with other two operation modes, the optimum calcium harness removal efficiencies of 85% and 57% could be reached in the induction cathode effluent and terminal effluent, respectively, at 8 mA cm-2 in the mode A. Increasing the current density from 5 to 20 mA cm-2 evidently promoted the removal of calcium hardness from 33% to 65% in the terminal effluent and the CaCO3 precipitation rate from 743 to 1462 gCaCO3 h-1 m-2 with the increased energy consumption from 0.53 to 2.2 kWh kg-1CaCO3. The optimized Ca2+/HCO3- molar ratio was 1:1.2 for the calcium hardness removal. In addition, increasing the flow rate into each cathode chamber from 10 to 40 mL min-1 gradually decreased from 67% to 35%. The calcium hardness was mainly removed in the forms of vaterite and calcite in the alkaline effluents and was marginally precipitated as aragonite and calcite on the cathodes surface. Generally, present energy-efficient electrochemical water softening system showed great potential for application in industrial processes.

Microcomb-based integrated photonic processing unit.

The emergence of parallel convolution-operation technology has substantially powered the complexity and functionality of optical neural networks (ONN) by harnessing the dimension of optical wavelength. However, this advanced architecture faces remarkable challenges in high-level integration and on-chip operation. In this work, convolution based on time-wavelength plane stretching approach is implemented on a microcomb-driven chip-based photonic processing unit (PPU). To support the operation of this processing unit, we develop a dedicated control and operation protocol, leading to a record high weight precision of 9 bits. Moreover, the compact architecture and high data loading speed enable a preeminent photonic-core compute density of over 1 trillion of operations per second per square millimeter (TOPS mm-2). Two proof-of-concept experiments are demonstrated, including image edge detection and handwritten digit recognition, showing comparable processing capability compared to that of a digital computer. Due to the advanced performance and the great scalability, this parallel photonic processing unit can potentially revolutionize sophisticated artificial intelligence tasks including autonomous driving, video action recognition and image reconstruction.

Investigation on the adverse impacts of electrochemically produced ClOx- on assessing the treatment performance of dimensionally stable anode (DSA) for Cl--containing wastewater.

The presence of chloride ions can facilitate the COD removal efficiency due to the involvement of active chlorine species in the electro-oxidation process, but few attentions have been paid to the negative effect of the electro-generated oxychlorides on electro-oxidation performance. In this study, the effects of oxychlorides were investigated as functions of current density and phenol concentration using DSA anodes in terms of the evaluation of the COD removal performance and the biological toxicity. The results show that oxychlorides formed in the electro-oxidation system could result in the over-evaluation of the COD removal performance. Increasing current density (15-50 mA cm-2) aggravated the over-evaluation of COD removal (4%-18%), owing to the enhancement in the electrochemical generation of oxychlorides. The increase of phenol concentration inhibited the production of oxychlorides, but the effect of oxychlorides on COD values at phenol concentration of 200 mg L-1 (82 mg L-1) was higher than that at 100 mg L-1 (51 mg L-1). The ClO3- was predominantly responsible for over-evaluation of the COD removal. In addition, bioassays with chlorella indicated that the electro-generated oxychlorides significantly increased the biological toxicity of the treated Cl--containing wastewater. This work provides new guidance for the correct evaluation of COD treatment performance and highlight the importance of minimizing toxic inorganic chlorinated byproducts during electro-oxidation of Cl--containing wastewater.

Laparoscopic single-layer running "trapezoid-shaped" suture versus mechanical stapling for esophagojejunostomy after total gastrectomy for gastric cancer: cost-effect analysis of propensity score-matched study cohorts.

OBJECTIVES: Totally laparoscopic total gastrectomy has been developed with difficulty in intracorporeal esophagojejunostomy. Although mechanical stapling has been widely used for intracorporeal esophagojejunostomy, manual suture holds great promise with the emergence of high-resolution 3D vision and robotic surgery. After exploration of how to improve the safety and efficiency of intracorporeal suture for esophagojejunostomy, we recommended the technique of single-layer running "trapezoid-shaped" suture. The cost-effectiveness was analyzed by comparing with conventional mechanical stapling. METHODS: The study retrospectively reviewed the patients undergoing laparoscopic gastrectomy for gastric cancer from January 2010 to December 2021. The patients were divided into two cohorts based on the methods of intracorporeal esophagojejunostomy: manual suture versus stapling suture. Propensity score matching was performed to match patients from the two cohorts at a ratio of 1:1. Then group comparison was made to determine whether manual suture was non-inferior to stapling suture in terms of operation time, anastomotic complications, postoperative hospital stay, and surgical cost. RESULTS: The study included 582 patients with laparoscopic total gastrectomy. The manual and stapling suture for esophagojejunostomy were performed in 50 and 532 patients, respectively. In manual suture cohort, the median time for the whole operation and digestive tract reconstruction were 300 min and 110 min. There was no anastomotic bleeding and stenosis but two cases of anastomotic leak which occurred at 3 days after surgery. The median length of postoperative hospital stay was 11 days. After propensity score matching, group comparison yielded two variables with statistical significance: time for digestive tract reconstruction and surgery cost. The manual suture cohort spent less money but more time for esophagojejunostomy. Intriguingly, the learning curve of manual suture revealed that the time for digestive tract reconstruction was declined with accumulated number of operations. CONCLUSIONS: Laparoscopic single-layer running "trapezoid-shaped" suture appears safe and cost-effective for intracorporeal esophagojejunostomy after total gastrectomy. Although the concern remains about prolonged operation time for beginners of performing the suture method, adequate practice is expected to shorten the operation time based on our learning curve analysis.

Chlorate induced false reduction in chemical oxygen demand (COD) based on standard dichromate method: Countermeasure and mechanism.

Deliberate addition of mildly oxidative chlorate (ClO3-), so-called "chemical oxygen demand (COD) remover", into wastewater in China or electrochemical production of ClO3- from Cl- induces the false COD reduction, which would bring about false appearance of effluents meeting the COD discharge standards. In this study, an easy sulfite-based reduction method was developed for the first time to remove ClO3- from the water samples before COD determination to eliminate this interference of ClO3-. In this reaction system, keeping the reaction temperature of sulfite reducing ClO3- at 60 °C was crucial for fast ClO3- removal rate, fixed molar [sulfite]ini/[chlorate]ini ratio value and the synchronous exhaustion of sulfite and ClO3-, which were of great significance for the real application of this improved COD determination method. The ClO3- interference on COD determination could be successfully eliminated after 20 min reduction of ClO3- by sulfite at pHini 4.0∼6.0 with the molar [sulfite]ini/[chlorate]ini ratio value in the range of 5∼6 when concentration of ClO3- was below 5 mM. Despite of the involvement of SO4·- in the sulfite reducing ClO3- system, the degradation of organic matters by SO4·- could be greatly impeded due to the lessened dissolved oxygen for SO4·- production at high reaction temperature and the scavenging of SO4·- by sulfite. In this reaction system, ClO2, ClO2- and ClO- were also generated and could be further reduced by sulfite stoichiometrically via oxygen transfer process with Cl- as the final product. In general, this study pioneered an effective, fast and convenient method for COD determination of the ClO3--laden wastewaters and evaluating the real electrochemical wastewater treatment performance in terms of COD removal.

Photochemical Reactivity of Humic Substances in an Aquatic System Revealed by Excitation-Emission Matrix Fluorescence.

The photochemical reactivity of humic substances plays a critical role in the global carbon cycle, and influences the toxicity, mobility, and bioavailability of contaminants by altering their molecular structure and the mineralization of organic carbon to CO2. Here, we examined the simulated irradiation process of Chinese standard fulvic acid (FA) and humic acid (HA) by using excitation-emission matrix fluorescence combined with fluorescence regional integration (FRI), parallel factor (PARAFAC) analysis, and kinetic models. Humic-like and fulvic-like materials were the main materials (constituting more than 90%) of both FA and HA, according to the FRI analysis. Four components were identified by the PARAFAC analysis: fulvic-like components composed of both carboxylic-like and phenolic-like chromophores (C1), terrestrial humic-like components primarily composed of carboxylic-like chromophores (C2), microbial humic-like overwhelming composed of phenolic-like fluorophores (C3), and protein-like components (C4). After irradiation for 72 h, the maximum fluorescence intensity (F max) of C1 and C2 of FA was reduced to 36.01-58.34%, while the F max of C3 of both FA and HA also decreased to 0-9.63%. By contrast, for HA, the F max of its C1 and C2 increased to 236.18-294.77% when irradiated for 72 h due to greater aromaticity and photorefractive tendencies. The first-order kinetic model (R 2 = 0.908-0.990) fitted better than zero-order kinetic model (R 2 = 0-0.754) for the C1, C2, and C3, of both FA and HA, during their photochemical reactivity. The photodegradation rate constant (k 1) of C1 had values (0.105 for FA; 0.154 for HA) that surpassed those of C2 (0.059 for FA, 0.079 for HA) and C3 (0.079 for both FA and HA) based on the first-order kinetic model. The half-life times of C1, C2, and C3 ranged from 6.61-11.77 h to 4.50-8.81 h for FA and HA, respectively. Combining an excitation-emission matrix with FRI and PARAFAC analyses is a powerful approach for elucidating changes to humic substances during their irradiation, which is helpful for predicting the environmental toxicity of contaminants in natural ecosystems.

From metal-organic frameworks to porous carbon materials: recent progress and prospects from energy and environmental perspectives.

Metal-organic frameworks (MOFs) have emerged as promising materials in the areas of gas storage, magnetism, luminescence, and catalysis owing to their superior property of having highly crystalline structures. However, MOF stability toward heat or humidity is considerably less as compared to carbons because they are constructed from the assembly of ligands with metal ions or clusters via coordination bonds. Transforming MOFs into carbons is bringing the novel potential for MOFs to achieve industrialization, and carbons with controlled pore sizes and surface doping are one of the most important porous materials. By selecting MOFs as a precursor or template, carbons with heteroatom doping and well-developed pores can be achieved. In this review, we discussed the state-of-art study progress made in the new development of MOF-derived metal-free porous carbons. In particular, the potential use of metal-free carbons from environmental and energy perspectives, such as adsorption, supercapacitors, and catalysts, were analyzed in detail. Moreover, an outlook for the sustainable development of MOF-derived porous carbons in the future was also presented.

Fabrication of N-doped carbons from waste bamboo shoot shell with high removal efficiency of organic dyes from water.

N-doped carbons were obtained from bamboo shoot shell via hydrothermal pretreatment under salt assistance followed by carbonization, using melamine as nitrogen source. The carbons with tubular morphology and surface areas in 406-489 m2/g range were used as adsorbents for the removal of methyl orange (MO) and rhodamine B (RhB). Adsorption isotherms and kinetic fitting showed much better accordance with Freundlich model and pseudo-second-order, showing balanced capacity (qe) of 50 mg/g for MO and 42 mg/g for RhB on the pristine carbons (BHC-800) at 25 °C. After N-doping treatment, carbons (BSC-M20) had qe of MO and RhB up to 140 and 100 mg/g, respectively, confirming a positive effect of N-doping on the enhancement of dyes removal. The findings indicated that hydrothermal treatment followed by carbonization was efficient to obtain N-doped carbons from biomass materials, and the present BSS-derived carbons were promising adsorbents for organic dyes removal from water.

Facile synthesis of a novel WO3/Ag2MoO4 particles-on-plate staggered type II heterojunction with improved visible-light photocatalytic activity in removing environmental pollutants.

A novel WO3/Ag2MoO4 heterojunction has been synthesized through a facile precipitation method with Ag2MoO4 particles firmly deposited on the surface of WO3 nanoplates, forming "particles-on-plate" type II heterojunction structures. This heterojunction exhibited improved photocatalytic activities for the degradation of rhodamine B (RhB), 4 chlorophenol (4-CP) and tetracycline hydrochloride (TC) under visible-light irradiation compared to pure Ag2MoO4 and WO3. In addition, the heterojunction with 10 wt% Ag2MoO4 displays the best photocatalytic performance, which was about 2 times better than that of pure WO3 or Ag2MoO4. The TC photodegradation rate reaches up to 91% within 90 min visible light irradiation. Furthermore, the photocatalytic efficiency of the Ag2MoO4/WO3 heterojunction is 1.3 times higher than that of the mixture of the two individual photocatalysts. This remarkable enhanced photocatalytic performance results from the staggered bandgap between Ag2MoO4 and WO3, which can suppress the recombination of electron-hole pairs efficiently. Moreover, based on the radical trapping experiment, the superoxide radical anions (·OH) and photogenerated holes (h+) are the crucial active oxidizing species.

Exceptional high selectivity of hydrogen/methane separation on a phosphonate-based MOF membrane with exclusion of methane molecules.

A phosphonate-based metal-organic framework membrane was constructed on a porous anodic alumina membrane (PAAM) substrate for H2/CH4 separation for the first time. Owing to the ultra-micro pore windows, this membrane exhibited effective size exclusion for CH4 molecules but suitable permeance for H2 molecules, giving rise to an exceptional high H2/CH4 separation selectivity.

Metal organic frameworks (MOFs) for magnetic solid-phase extraction of pyrazole/pyrrole pesticides in environmental water samples followed by HPLC-DAD determination.

Magnetic metal-organic frameworks (MOFs, [MIL-101]) were prepared and used as magnetic solid-phase extraction (MSPE) adsorbents for preconcentration of four kinds of pyrazole/pyrrole pesticides (flusilazole, fipronil, chlorfenapyr, and fenpyroximate) in environmental water samples, followed by high-performance liquid chromatography-diode-array detector (HPLC-DAD) determination. Several variables affecting MSPE efficiency were systematically investigated, including amount of MIL-101, extraction time, sample pH, salt concentration, type of desorption solvent and desorption number of times. Under optimized conditions, excellent linearity was achieved in the range of 5.0-200.0µg/L for flusilazole and fipronil, and 2.0-200.0µg/L for chlorfenapyr and fenpyroximate, with correlation coefficients r>0.9911. Limits of detection and quantification were 0.3-1.5µg/L and 1.0-5.0µg/L, respectively. The intra-day and inter-day precision (relative standard deviation, n=6, %) at three spiked levels were 1.1-5.4% and 3.9-7.8% in terms of peak area, respectively. The method recoveries at three fortified concentration levels ranged from 81.8% to 107.5% for reservoir water samples, 81.0-99.5% for river water samples, and 80.2-106.5% for seawater samples. The developed MOFs based MSPE coupled with HPLC method proved to be a convenient, rapid and eco-friendly alternative to the sensitive determination of pyrazole/pyrrole pesticides with high repeatability and excellent practical applicability.

Increasing the CO2 /N2 Selectivity with a Higher Surface Density of Pyridinic Lewis Basic Sites in Porous Carbon Derived from a Pyridyl-Ligand-Based Metal-Organic Framework.

The development of functional porous carbon with high CO2 /N2 selectivity is of great importance for CO2 capture. In this paper, a type of porous carbon with doped pyridinic sites (termed MOFC) was prepared from the carbonization of a pyridyl-ligand based MOF. Four MOFCs derived from different carbonizing temperatures were prepared. Structural studies revealed high contents of pyridinic-N groups and nearly the same pore-size distributions for these MOFCs. Gas-sorption studies revealed outstanding CO2 uptake at low pressures and room temperature. Owing to the high content of pyridinic-N groups, the CO2 /N2 selectivity on these MOFCs exhibits values of about 40-50, which are among the top values in carbon materials. Further correlation studies demonstrated that the CO2 /N2 selectivities show a positive linear relationship with the surface density of pyridinic-N groups, thus validating the synergistic effect of the doped pyridinic-N groups on CO2 adsorption selectivity.

[Hybrid procedures for multilevel femoral and popliteal artery occlusive disease].

OBJECTIVE: To evaluate the immediate and mid-term effectiveness of hybrid procedures (combined open surgery and endovascular therapy) for multilerel femoral and popliteal artery occlusive disease. METHODS: Between June 2009 and June 2012, 22 cases of severe femoral and popliteal artery occlusive disease were treated by hybrid surgery. There were 15 men and 7 women with an age range of 52-78 years (mean, 66.2 years) and with a disease duration of 6 months to 5 years (mean, 1.5 years). Of 22 patients, 13 had a history of smoking; 8 were classified as Fontaine III and 14 as Fontaine IV. The complications included diabetes (8 patients), hypertension (16 patients), hyperlipemia (10 patients), coronary heart disease (11 patients), and chronic kidney failure (1 patient). Patency analyses were performed using Kaplan-Meier life tables and log-rank test. RESULTS: All patients underwent successfully procedures. The time of operation was 70-160 minutes (mean, 137 minutes). Acute myocardial infarction, hematoma of incision, fracture of stent, and stent thrombosis occurred in 1 case, respectively. At 6 months after surgery, the ankle brachial index (ABI), the transcutaneous oxygen pressure (TcpO2), and the average intermittent claudication distance were significantly increased when compared with preoperative ones [0.79 +/- 0.33 versus 0.32 +/- 0.18, (42.7 +/- 15.7) kPa versus (17.6 +/- 11.6) kPa, and (420 +/- 80) m versus (160 +/- 54) m, P < 0.05]. The patients were followed up 6-24 months (mean, 14.5 months). The primary patency rate, primary assisted patency rate, and second patency rate were 77.3% (17/22), 90.9% (20/22), and 95.5% (21/22) respectively, showing no significant difference among them (P > 0.05). No significant difference was found in various-stage patency rates between patients at Fontaine III and IV (P > 0.05). CONCLUSION: Hybrid procedures provide an effective treatment of multilevel femoral artery and popliteal artery disease while there is good outflow.

[Comparison of early complications in treatment of carotid artery stenosis with carotid endarterectomy and carotid stenting].

OBJECTIVE: To compare the early complications of carotid stenting (CAS) and carotid endarterectomy (CEA) in treatment of carotid artery stenosis. METHODS: Between January 2005 and December 2007, 63 patients with carotid artery stenosis were treated with CEA in 36 cases (CEA group) and with CAS in 27 cases (CAS group). There were 42 males and 21 females with an average age of 67.5 years (range, 52-79 years). The locations were the left side in 28 cases and the right side in 35 cases. The carotid stenosis was 60%-95% (mean, 79%). The major clinical symptoms were stroke and transient ischemic attack. The cranial CT showed old cerebral infarction in 24 cases, lacunar infarction in 22 cases, and no obvious abnormal change in 17 cases. The encephalon, heart, and local complications were compared between 2 groups within 7 days after operation. RESULTS: In CEA group, encephalon complications occurred in 3 cases (8.3%), heart complications in 2 cases (5.6%), and local complications in 5 cases (13.9%); while in CAS group, encephalon complications occurred in 8 cases (29.6%), heart complications in 1 case (3.7%), and local complications in 3 cases (11.1%). The encephalon complication ratio of CAS group was significantly higher than that of CEA group (chi2 = 4.855, P = 0.028); and there was no significant difference in other complications ratios between 2 groups (P > 0.05). CONCLUSION: CEA is the first choice to treat carotid artery stenosis.