Low Mass Transfer Research Articles

Waste-Wood-Isolated Cellulose-Based Activated Carbon Paper Electrodes with Graphene Nanoplatelets for Flexible Supercapacitors

Waste wood, which has a large amount of cellulose fibers, should be transformed into useful materials for addressing environmental and resource problems. Thus, this study analyzed the application of waste wood as supercapacitor electrode material. First, cellulose fibers were extracted from waste wood and mixed with different contents of graphene nanoplatelets (GnPs) in water. Using a facile filtration method, cellulose papers with GnPs were prepared and converted into carbon papers through carbonization and then to porous activated carbon papers containing GnPs (ACP−GnP) through chemical activation processes. For the morphology of ACP−GnP, activated carbon fibers with abundant pores were formed. The increase in the amount of GnPs attached to the fiber surfaces decreased the number of pores. The Brunauer–Emmett–Teller surface areas and specific capacitance of the ACP−GnP electrodes decreased with an increase in the GnP content. However, the galvanostatic charge–discharge curves of ACPs with higher GnP contents gradually changed into triangular and linear shapes, which are associated with the capacitive performance. For example, ACP with 15 wt% GnP had a low mass transfer resistance and high charge delivery of ions, resulting in the specific capacitance value of 267 Fg−1 owing to micropore and mesopore formation during the activation of carbon paper.

Rhenium extraction from dilute solution by precipitation flotation and oxidative volatilization techniques

The low mass transfer effect of dilute solution results in low recovery efficiency of critical metal Re ions from ultralow-concentration metallurgical industrial effluents. Bubble driving was an effective measure to enhance the mass transfer in the dilute solution, and bubble flotation technology was adapted to enrich and recover metal ions. In this work, the extraction of critical metal Re from dilute solutions by a precipitation flotation process was investigated. The precipitation flotation process includes ion precipitation by CTAB and ammonium salt, flocculation by PAM and air bubble flotation separation. The effects of technical parameters on Re recovery were systematically investigated. In the precipitation stage, NH4+ with a positive charge firstly reacts with the rhenate (ReO4-) with a negative charge via electrostatic action and then further reacts with CTAB to form fine CTAB(NH4ReO4) precipitate through complexation coordination. In the flocculation procedure, the particle size of precipitate flocs is elevated due to the physical polymerization of PAM polymer. In the flotation procedure, the long carbon chains on the surface of the flocs have a foaming effect due to their strong hydrophobicity, and they are trapped by the upfloated bubbles and rapidly enriched in the foams. Under the optimized conditions, the recovery efficiency of Re is 99.5% and qualified circulating water with a turbidity of 9.8 is obtained. Eventually, highly purified Re oxides (99.8%) are prepared from the Re froth product via oxidizing volatilization since the utilized organic CTAB and PAM can be burned completely during the oxidizing calcination process.

Regulation Strategy of Nanostructured Engineering on Indium-Based Materials for Electrocatalytic Conversion of CO2.

Electrochemical carbon dioxide reduction (CO2 RR), as an emerging technology, can combine with sustainable energies to convert CO2 into high value-added products, providing an effective pathway to realize carbon neutrality. However, the high activation energy of CO2 , low mass transfer, and competitive hydrogen evolution reaction (HER) leads to the unsatisfied catalytic activity. Recently, Indium (In)-based materials have attracted significant attention in CO2 RR and a series of regulation strategies of nanostructured engineering are exploited to rationally design various advanced In-based electrocatalysts, which forces the necessary of a comprehensive and fundamental summary, but there is still a scarcity. Herein, this review provides a systematic discussion of the nanostructure engineering of In-based materials for the efficient electrocatalytic conversion of CO2 to fuels. These efficient regulation strategies including morphology, size, composition, defects, surface modification, interfacial structure, alloying, and single-atom structure, are summarized for exploring the internal relationship between the CO2 RR performance and the physicochemical properties of In-based catalysts. The correlation of electronic structure and adsorption behavior of reaction intermediates are highlighted to gain in-depth understanding of catalytic reaction kinetics for CO2 RR. Moreover, the challenges and opportunities of In-based materials are proposed, which is expected to inspire the development of other effective catalysts for CO2 RR.

Constructing an Ultra-Rapid Nanoconfinement-Enhanced Fluorescence Clinical Detection Platform by Using Machine Learning and Tunable DNA Xerogel "Probe".

Low mass transfer efficiency and unavoidable matrix effects seriously limit the development of rapid and accurate determination of biosensing systems. Herein, we have successfully constructed an ultra-rapid nanoconfinement-enhanced fluorescence clinical detection platform based on machine learning (ML) and DNA xerogel "probe", which was performed by detecting neutrophil gelatinase-associated lipocalin (NGAL, protein biomarker of acute kidney injury). By regulating pore sizes of the xerogels, the transfer of NGAL in xerogels can approximate that in homogeneous solution. Due to electrostatic attraction of the pore entrances, NGAL rapidly enriches on the surface and inside the xerogels. The reaction rate of NGAL and aptamer cross-linked in xerogels is also accelerated because of the nanoconfinement effect-induced increasing reactant concentration and the enhanced affinity constant KD between reactants, which can be promoted by ∼667-fold than that in bulk solution, thus achieving ultra-rapid detection (ca. 5 min) of human urine. The platform could realize one-step detection without sample pretreatments due to the antiligand exchange effect on the surface of N-doped carbon quantum dots (N-CQDs) in xerogels, in which ligand exchange between -COOH and underlying interfering ions in urine will be inhibited due to higher adsorption energy of -COOH on the N-CQD surface relative to the interfering ions. Based on the ML-extended program, the real-time analysis of the urine fluorescence spectra can be completed within 2 s. Interestingly, by changing DNA, aptamer sequences, or xerogel fluorescence intensities, the detection platform can be customized for targeted diseases.

Cobalt sulfide nanosheets synthesized by anion exchange method for efficient Hg0 removal from flue gas

Transition metal sulfide adsorption has been recognized as a potential method for Hg0 removal, and the physicochemical properties of the adsorbent can significantly affect the Hg0 removal efficiency. The nanosheet structure with abundant unsaturated surface atoms can result in lower mass transfer resistance and give more adsorption sites. Thus, in the present work, cobalt sulfide nanosheet adsorbents with different Co/S ratio were synthesized by anion exchange method. Characterization results show that CS-10 has the lowest crystallinity and the highest Co3+/Co2+ and S22−/S2− ratio. These results give CS-10 the best Hg0 removal efficiency of nearly 100 % at a high GHSV of 180 000 h−1 at 60 °C. In addition, CS-10 has a good resistance to SO2 whose Hg0 removal efficiency decrease after SO2 introduction but recover to original level after SO2 cutting off. After being impregnated in Na2S solution, the adsorption efficiency of the used CS-10 can be easily regenerated. XPS results show that HgS can resolve in Na2S solution via HgS(ad) + S2− → [HgS2]2−. Furthermore, Co3+ and S22− as the main active sites for Hg0 removal can be replenished during the impregnation in Na2S solution. Kinetic study points that Hg0 adsorption characteristics on CS-10 obey pseudo-first-order and pseudo-second-order kinetic models, suggesting that the Hg0 diffusion on the external surface and the reaction at the adsorption site can both influence the Hg0 removal process.

The effect of inlet design and developing flow on local mass transfer in electrolyzers

The mass transfer performance of electrolyzers can vary significantly depending on the type of inlet that is used. Furthermore, significant local effects can occur if the flow is not distributed well by the inlet. In this work, these effects are investigated using segmented electrodes. With a tube inlet, the formation of a jet results in regions of low and high mass transfer. With a conic inlet, significant flow channeling to the sides of the electrolyzer is observed. These local effects were reduced by using a divider inlet, the addition of a calming section, or a turbulence promoter. The type of inlet also determines the flow regime: with the extended conic configuration the flow is developed laminar, whereas with the tube inlet the flow is developing turbulent. The cross-sectional area ratio of the inlet to the channel was found to be an important parameter in predicting the local mass transfer behavior.

Construction of hierarchical Sn-ECNU-7 zeolite with MWW nanosheets for Baeyer-Villiger oxidation of bulky reactant

The Baeyer-Villiger (BV) oxidation which can transform ketones into the corresponding lactones attracts wide attention. Although many Sn-containing zeolites have shown superior activity, bulky reactants often suffer low mass transfer efficiency during BV reaction due to the narrowed channel opening of microporous zeolite catalysts. To address this issue, we developed a preparation method to construct the swollen-type Sn-MWW zeolite, namely Sn-ECNU-7P, in which cetyltrimethylammonium bromide (CTAB) surfactant successfully swollen the adjacent MWW nanosheets with a large interlayer spacing of 22 Å during hydrothermal synthesis. The subsequent of acid treatment and calcination led to the formation of a hierarchical porous system in the resulting Sn-ECNU-7 zeolite with a high external surface area. Compared to conventional Sn-MWW catalysts, Sn-ECNU-7 exhibited a higher activity and stability for the BV oxidation reaction of bulky 2-adamantanone using H2O2 and tert-butyl hydroperoxide (TBHP) as oxidants, showing a promising potential for the application in BV oxidation of bulky reactants.

Optimal fabrication of carbon paper by different lengths of chopped carbon fibers and its enhanced performance in proton exchange membrane fuel cell

Carbon paper as a macroporous substrate of gas diffusion layer in proton exchange membrane fuel cells directly impacts the output performance of cells. In this study, we present a straightforward strategy to improve the overall performance of carbon paper by mixing short/long (6mm/10 mm) chopped carbon fibers at an optimal concentration of phenolic resin. The results show that incorporating longer carbon fibers can increase the porosity, conductivity, gas flux, and mechanical properties of carbon paper. The membrane electrode assembly achieved a peak power density of 1182.61 mW cm−2 at 60% RH using carbon paper with a long carbon fiber content of 40 wt% and an impregnation concentration of 10 wt%. This outperforms commercially available carbon paper. Based on electrochemical impedance spectroscopy results, it was confirmed that our carbon paper had a lower mass transfer resistance of only 32.17 mΩ cm−2 under conditions of 2 A cm−2 and 60% RH. This was due to its sparser three−dimensional network-like pore structure which was created by mixing different lengths (6mm/10 mm) of carbon fibers. This work provides new insights into preparing high−performance carbon papers.

Sandwich-like adsorbent based on Al-fumarate MOF coating on Cu@CuxS sheet for rapid solar-driven atmospheric water harvesting

Atmospheric water harvesting (AWH) technology using MOFs as an adsorbing medium has been considered a favorable approach to alleviate water scarcity, while its practical implementation is hindered due to the low mass and heat transfer efficiency of MOFs. To solve it, we presented a solar-driven sandwich-like adsorbent (Al-Fu@Cu@CuxS) for rapid AWH, with CuxS layer, Cu layer and Al-fumarate MOF coating from top to bottom. In Al-Fu@Cu@CuxS, Al-Fu coating and CuxS layer respectively function as a water vapor cage and solar energy catcher, for water vapor absorption–desorption and photothermal conversion, and Cu among them with high thermal conductivity can quickly transfer heat to achieve rapid water generation. The experimental results showed that the resultant Al-Fu@Cu@CuxS could reach a saturated water uptake of 0.223 g/g due to a high specific surface area (1033.19 m2/g) of Al-Fu skeleton. With the assistance of CuxS, Al-Fu@Cu@CuxS could heat to 70.4 °C under 1 sun illumination and achieve 93.3 % water desorption within 50 min, and its photothermal conversion efficiency was as high as 95.2 %. Furthermore, in a matched AWH device, the collection water capacity of Al-Fu@Cu@CuxS was 2.14 g/cycle, much higher than that of powdered Al-Fu of 0.69 g/cycle, revealing its application potential in AWH.

Effect of bubble morphology and behavior on power consumption in non-Newtonian fluids’ aeration process

Due to a prolonged operation time and low mass transfer efficiency, the primary challenge in the aeration process of non-Newtonian fluids is the high energy consumption, which is closely related to the form and rate of impeller, ventilation, rheological properties and bubble morphology in the reactor. In this perspective, through optimal computational fluid dynamics models and experiments, the relationship between power consumption, volumetric mass transfer rate (kLa) and initial bubble size (d0) was constructed to establish an efficient operation mode for the aeration process of non-Newtonian fluids. It was found that reducing the d0 could significantly increase the oxygen mass transfer rate, resulting in an obvious decrease in the ventilation volume and impeller speed. When d0 was regulated within 2–5 mm, an optimal kLa could be achieved, and 21% of power consumption could be saved, compared to the case of bubbles with a diameter of 10 mm.

Facile fabrication of hollow molecularly imprinted polymer microspheres via pickering emulsion polymerization stabilized with TiO2 nanoparticles

The polymer microspheres with hollow structure are of technological importance in the removal of pollutants because of the large specific surface area and low mass transfer resistance. In this work, we employ the Pickering emulsion polymerization stabilized with TiO2 nanoparticles to build the molecularly imprinted polymers microspheres with hollow structure (H-MIPs) for the precise recognition of dibutyl phthalate (DBP), which would influence the biological reproductive system and endocrine system as a typical endocrine disrupting compound. The polymerization induced phase separation occurring within Pickering emulsion droplets plays a significant role in the formation of hollow structure. The morphology and structure of H-MIPs were observed via optical microscope and field emission scanning electron microscope, respectively. The results indicate that H-MIPs microspheres are of irregular spherical form with sunken surface and perfect hollow structure. The forming process of the hollow structure was analyzed in detail. Besides, the chemical structure and thermal stability of H-MIPs and H-NIPs were characterized by fourier transform infrared spectroscopy and thermal gravimetric analysis, respectively. The binding performance of H-MIPs and H-NIPs was investigated through a series of binding experiments, which consist of the binding kinetics, binding isotherm, selective test and reusability experiment. The results show that H-MIPs microspheres exhibit remarkable binding kinetics towards DBP, and the saturated adsorption time is not more than 30 min. Apart from the fast binding rate, H-MIPs also show considerable binding amount, accurate binding selectivity and good regenerability. The imprinting factor could reach to 2.56, and the binding amount towards DBP remains at a relatively high level within 3 cycles. The prepared H-MIPs microspheres have broad application prospects in environmental and analytical field involved DBP, and the study also offers an alternative method for the facile building of H-MIPs microspheres.

Leaching Behavior of Rare Earth Elements and Aluminum from Weathered Crust Elution-Deposited Rare Earth Ore with Ammonium Formate Inhibitor

In situ leaching of weathered crust elution-deposited rare earth ore usually uses ammonium sulfate as the leaching agent, which poses challenges such as low mass transfer efficiency, high consumption of the leaching agent and long leaching periods. In order to intensify the leaching process of rare earth elements and reduce the impurity of leaching accompanying rare earth, ammonium sulfate and ammonium formate were mixed as a novel compound leaching agent to treat weathered crust elution-deposited rare earth ore. The effects of ammonium formate concentration, liquid/solid ratio, leaching agent pH and leaching temperature on the leaching process of rare earth (RE) and aluminum (Al) were investigated and evaluated using the chromatographic plate theory. Results showed that ammonium formate could effectively enhance the mass transfer efficiency of rare earth and significantly inhibit the mass transfer efficiency of aluminum. Leaching agent pH has a greater impact on the mass transfer efficiency of aluminum. A higher leaching temperature could enhance the mass transfer efficiency of rare earth and aluminum by providing a driving force to overcome the resistance of diffusion. The optimum conditions for leaching rare earth and aluminum are 0.1 mol/L ammonium sulfate compounded with 0.032 mol/L ammonium formate, pH 4–8 of the leaching agent, 0.8:1 liquid:solid (mL/g) ratio and room temperature. Under this condition, the mass transfer efficiency of rare earth was improved, and the mass transfer efficiency of aluminum was significantly inhibited.

Titanium mesh as the anode of electrochemically active biofilm sensor for improved sensitivity in water toxicity real-time early-warning

As serious water ecological pollution caused by toxicant leakage occurs frequently, early-warning for toxicity presented in water environment attracts increasing attentions as it saves time to retain water safety and human health. Electrochemically active biofilm (EAB) sensor is a promising device for in situ real-time water toxicity early-warning. To improve the sensitivity of EAB sensor particularly for low-concentration toxicity warning, this study employed titanium mesh (TiM) as the anode to construct an EAB sensor. Compared to traditional EAB sensor with carbon felt (CF) anode, the sensitivity of the TiM sensor was increased up to 37.4 times. The effects of mesh size (TiM50, TiM100, TiM150) and operation mode (flow-by and flow-through) on the sensitivity of TiM sensors were further investigated. Results showed the sensor with TiM100 anode had the highest inhibition rate (IR) in flow-by mode, attributed to low charge transfer resistance (Rct) and fast mass transfer. Flow-through operation could further enhance TiM100 sensor's sensitivity from flow-by operation and succeeded to signal as low as 0.0025% formaldehyde, the lowest so far tested in EAB sensor with sensing anode. Multiple toxicity shocks on flow-through TiM100 sensor revealed its good recoverability towards all tested formaldehyde concentration from 0.01% to 0.0025%, during which electrochemical activity degradation and biomass accumulation partially impaired the repeatability. This work highlights the great improvement of EAB sensors by utilizing titanium mesh as EAB carrier and provides a reference for the practical application of metallic materials for EAB sensors.

Effect of Blended Perfluorinated Sulfonic Acid Ionomer Binder on the Performance of Catalyst Layers in Polymer Electrolyte Membrane Fuel Cells.

In this study, blended perfluorinated sulfonic acid (PFSA) ionomers with equivalent weights (EWs, g/mol) of ~1000, 980, and 830 are prepared. Catalyst layers (CLs), using blended PFSA ionomers, with different side chain lengths and EWs are investigated and compared to CLs using single ionomers. The ion exchange capacity results confirm that blended ionomers have the target EWs. As a result, blended ionomers exhibit higher ion conductivity than single ionomers at all temperatures due to the higher water uptake of the blended ionomers. This implies that blended ionomers have a bulk structure to form a competent free volume compared to single ionomers. Blended ionomers with short side chains and low EWs can help reduce the activation energy in proton conduction due to enhanced hydrophobic and hydrophilic segregation. In addition, when using the blended ionomer, the CLs form a more porous microstructure to help reduce the resistance of oxygen transport and contributes to lower mass transfer loss. This effect is proven in fuel cell operations at not a lower temperature (70 °C) and full humidification (100%) but at an elevated temperature (80 °C) and lower relative humidity (50 and 75%). Blended ionomer-based CLs with a higher water uptake and porous CL structure result in improved fuel cell performance with better mass transport than single ionomer-based CLs.

Bubble dynamic behaviors in the anode porous transport layer of proton exchange membrane electrolyzers using a microfluidic reactor

Gas bubbles in proton exchange membrane (PEM) electrolyzers are the main source of mass transport loss in the porous transport layer at high current densities. However, the complexity and opacity of the porous transport layer make it challenging. In this study, a microfluidic reactor with an electrochemical reaction boundary is designed to observe the bubble behaviors in the porous transport layer. The detailed bubble growth and detachment mechanisms are explored based on the visualization results. Results show that the gas phase evolution undergoes the unsteady growth stage and the steady stage. Bubble behaviors including free movement, coalescence, breakthrough and detachment are observed for a single bubble in the porous transport layer. The gas phase saturation in the porous transport layer as well as the applied voltage increases with increasing the current density. Moreover, as the flow rate increases, the time for the first bubble detachment and the number of bubble detachment gradually decrease, and the average detachment radius of the bubble gradually increases. A lower applied voltage is needed under a higher flow rate due to low mass transfer resistance. The proposed method can help us understand the dynamic behavior of bubbles in the porous transport layer of PEM electrolyzers.

A monolithic stationary phase with dendritic nanostructures for the separation of PEGylated proteins.

Separation of PEGylated protein mixtures into individual species is a challenging procedure, and many efforts have been focused on creating novel chromatographic supports for this purpose. In this study, a new monolithic stationary phase with hyperbranched nanostructures was chemically synthesized. For this, monoliths with a support matrix of poly (glycidyl methacrylate-co-ethylene dimethacrylate) and ethylenediamine chemistry were modified with third-generation dendrons with butyl-end groups. The new monolith was analyzed by infrared spectroscopy, confirming the dendron with butyl ligands and exhibited low mass transfer resistance as observed by breakthrough frontal analysis. This support was able to separate mono-PEG ribonuclease A from the PEGylation mixture, indicated by a single band (∼30kDa) in the electrophoretic analysis. Moreover, the separation of mono-PEGylated positional isomers was probably observed, as the protein with ∼30kDa was found in two separate peaks. Interestingly, the dendronized monolith allowed the separation of the reaction mixture into individual PEGylated species when using high ammonium sulfate concentrations (2M). A correlation between the PEGylation degree and the strength of the hydrophobic interactions on the monolith was observed. This chromatographic approach combines the natural branched architecture of dendrons and the higher capabilities of the monoliths enhancing the hydrophobic surface area, and therefore the interaction between the PEGylated proteins and ligands. Thus, the novel support represents a novel platform for the purification of PEGylated from non-PEGylated proteins with biotechnological applications.

Investigation of surfactant effect on ozone bubble motion and mass transfer characteristics

The low solubility and low mass transfer efficiency of ozone (O3) in water are important reasons for limiting the application of ozone oxidation technology and advanced ozone oxidation technology. Low-dose surfactants were introduced to affect the behavior of ozone bubbles, influencing the ozone mass transfer efficiency. The motion of ozone bubbles in three different types of surfactant solutions (polyoxyethylene lauryl ether (Brij35), sodium dodecylsulfate (SDS), and cetyltrimethylammonium bromide (CTAB)) was observed. The decrease in surface tension led to a decrease in bubble size, a tendency to spherical shape, an increase in gas content and residence time, a decrease in lateral displacement of a single bubble, and a more stable trajectory. The effect of surfactants on ozone mass transfer was further investigated. The addition of surfactant was found to increase the gas-liquid interface area but decrease the liquid phase mass transfer coefficient, and the extent of the two opposite effects varied for different surfactants. The analysis combined with the removal of pollutant p-Nitrophenol (PNP) showed that the addition of the nonionic surfactant Brij35 and the anionic surfactant SDS inhibited ozone mass transfer, while low concentrations of the cationic surfactant CTAB enhanced ozone mass transfer. When the CTAB concentration was 3 mg L−1, the ozone volume mass transfer coefficient reached a maximum of 0.2902 min−1.

A novel insight of degradation ibuprofen in aqueous by catalytic ozonation with supported catalyst: Supports effect on ozone mass transfer

Catalytic ozonation is an effective wastewater purification process. However, the low ozone mass transfer in packed bubble columns leads to low ozone utilization efficiency (OUE), poor organic degradation performance, and high energy consumption. Therefore, there is an urgent need to develop efficient supported catalysts that can enhance mass transfer and performance. However, the reaction mechanism of the support on ozone mass transfer remains unclear, which hinders the development of catalytic ozonation applications. In this study, lava rocks (LR)-supported catalysts, specifically CuMn2O4@LR and MnO2Co3O4@LR, were proposed for catalytic ozonation of IBP degradation due to their superior catalytic activity, stability, and high OUE. Addition of CuMn2O4@LR or MnO2Co3O4@LR increased IBP removal efficiency from 85% to 91% or 88%, and reduced energy consumption from 2.86 to 2.14 kWh/m3 or 2.60 kWh/m3, respectively. This improvement was attributed to LR-supported catalysts enhancing mass transfer and promoting O3 decomposition to generate •OH and •O2−, leading to IBP degradation. Furthermore, this study investigated the effects of ozone dose, supporter sizes, and catalyst components on ozone-liquid mass transfer. The results revealed that the size of the supporter influenced stacked porosity and consequently affected ozone mass transfer. Larger-sized LR (kLa= 0.172 min−1) exhibited better mass transfer compared to smaller-sized supports. Based on these findings, it was concluded that both CuMn2O4@LR and MnO2Co3O4@LR are potential catalysts for catalytic ozonation in residual IBP degradation of pharmaceutical wastewater, and LR showed good credibility as a catalyst supporter. Understanding the effects of supporters and active components on ozone mass transfer provides a fundamental principle for designing supported catalysts in catalytic ozonation applications.

Performance analysis of heat and mass transfer, thermodynamic and economic of high gravity direct contact evaporation system

Based on the problem of low heat and mass transfer efficiency and low heat utilization rate in the process of efficient utilization and treatment of low-grade waste heat, the high gravity direct contact evaporation (HG-DCE) system driven by industrial waste heat is proposed. The heat and mass transfer properties in HG-DCE process were studied by simulated with hot water and air at room temperature, and the thermodynamic and economic properties were further analyzed in detail. Results showed that the evaporation intensity of the HG-DCE system could reach 1523 kg/(m3·h), and the volume heat and mass transfer coefficients could reach 270.77 kW/(m3·°C) and 12.23 kg/(m3·s), respectively. According to the established analysis models of entropy generation and exergy loss, the rule of irreversibility of system was obtained, and the highest exergy efficiency was higher than 90.0 % at the gas-liquid mass ratio of 1:1. Simultaneously, the evaporation heat of system accounted for 40.0 % of the supplied heating enthalpy, and the evaporation cost about 0.094 $/kg could be easily achieved. The perfect performance and advantages of HG-DCE system were further confirmed, which provided a new method for using low grade heat for seawater desalination and wastewater treatment.

Fast g-C3N4 sonocoated activated carbon for enhanced solar photocatalytic oxidation of organic pollutants through Adsorb & Shuttle process

To solve low mass transfer in photocatalytic technology for water treatment, the combination of photoactive nanoparticles with highly adsorptive materials has been regarded as a successful approach. The optimization of photoactive particle coating in terms of dispersion on the surface of adsorbing support is the main key to reach a maximum synergism for pollutants removal. This study discusses the coating of as-prepared biomass based activated carbon by g-C3N4 using three routes, namely ball milling (AC-CN@BM), physical stirring (AC-CN@Phy) and ultrasonic assisted coating (AC-CN@US). The coating mechanisms by different processes were discussed using different characterization techniques. Ball milling based coating provides good g-C3N4 dispersion on the surface of AC, however, a partial degradation of g-C3N4 structure and a lower surface area were confirmed by FTIR, XRD and BET analysis. Physically designed sample shows a significant agglomeration of particles on the surface of AC. However, ultrasonic coating provides excellent distribution of g-C3N4 and high surface of the composite. In terms of photoactivity, AC-CN@BM exhibits the lowest adsorption and photocatalytic activity under solar light for the removal of ciprofloxacin. AC-CN@Phy showed medium performance, but less physical stability of g-C3N4 particles on AC, leading to their partial release. AC-CN@US showed the highest efficiency and stability after using; suggesting the good combination between g-C3N4 and AC, which in turn maximizes the removal of ciprofloxacin via Adsorb & shuttle process. The overall costs of composite, including the starting elements and the coating ultrasonic process are relatively low and green as compared to commonly reported routes.