Initial NaCl Concentration Research Articles

Tailoring iron MOF/carbon nanotube composites as flow electrodes for high-performance capacitive deionization

Capacitive deionization techniques are of interest in water treatment technology due to their low cost, excellent efficiency, and environmental friendliness. Currently, metal–organic frameworks are highly impactful candidates for use as electrode materials in electrochemistry. It provides a large pore volume, good chemical stability, and a high specific surface area. Tuning metal–organic frameworks with carbon materials will have a good impact on electrode materials with increasing performance. This study shows a facile and effective strategy for arranging flow capacitive desalination technology for salt removal. The conducting network of Fe-MOF/CNTs provides rapid electron transport and offers a high diffusion length of ions. This material exhibited excellent desalination performance, with a high salt adsorption of 80.575 mg/g at 1.6 V at an initial NaCl concentration of 1000 mg/L. Overall, the facile method and fabrication strategy greatly advances water treatment applications.

Sodium doping and control during the preparation of α-hemihydrate gypsum in NaCl solution

Transformation of phosphogypsum (PG) into α-hemihydrate gypsum (α-HH) in sodium salt solution is disturbed by the doping of Na+, which causes the frost of Na+ doped α-HH. In this study, the content evolution of Na+ impurities into α-HH was clarified during the hydrothermal process at 95 ℃, the frost phenomenon of hardened gypsum containing Na+ impurities was observed and controlled. The results show that increasing the initial NaCl concentration from 5 % to 25 % can promote the phase conversion of PG into α-HH within 30 min, but this will increase the Na2O content in the product from 0.08 % to 4.37 %, which is due to the formation of the undesirable phase Na2SO4·5CaSO4·3H2O. The content of Na+ impurities entering α-HH presents a non-linear increase with the NaCl solution concentration and reaction time, which can be well described by Boltzmann function. An obvious frost phenomenon of the hardened plaster of Na+ doped α-HH can be observed after curing 3 d, and the frost is identified as Na2SO4. This work further demonstrates the feasibility that the addition of CaCl2 in NaCl solution is an effective approach to control the doping of Na+ into α-HH, the Na2O content decreases to 0.97 % in the mixed solution of 17.5 % NaCl and 10 % CaCl2, this helps to eliminate the frost phenomenon and improve the mechanical strength of α-HH.

Simulation and Experimental Study of Circulatory Flash Evaporation System for High-Salt Wastewater Treatment

Treatment methods for high-salt wastewater mainly consist of physical methods, chemical methods and biological methods. However, there are some problems, such as slow treatment speed, high investment costs and low treatment efficiency. To address NaCl solutions, in this study, a circulatory flash system was designed based on gas–liquid equilibrium, mass conservation equation and energy conservation equation. A circulatory flash evaporation simulation and a static flash evaporation experiment were conducted on NaCl solutions under various operating conditions to investigate the effects of heating temperature, flash pressure and initial NaCl concentration on the circulatory flash evaporation system. The significance of each factor’s influence on the evaporation fraction and energy consumption was examined through static flash experiments. The simulation results demonstrated that increasing the heating temperature, decreasing the flash pressure and having a higher initial NaCl concentration could enhance the treatment capacity of high-salt wastewater. The flow rate of vapor outlets increased with higher heating temperature but decreased as the flash pressure rose. The experimental results demonstrated that flash evaporation pressure was the primary factor influencing both the evaporation fraction and the energy consumption per unit mass of vapor produced. It was observed that with an increase in heating temperature, the flash pressure decreased and there was a corresponding decrease in energy consumption per unit mass of vapor produced. The optimal experimental conditions were achieved at a heating temperature of 99 °C, a flash pressure of 15 kPa, and an initial NaCl concentration of 20%.

The AA7075–CS1018 Galvanic Couple under Evaporating Droplets

The galvanic corrosion behavior of the AA7075–CS1018 couple was examined in dynamic electrolytes using the ZRA technique. A modified electrochemical setup was developed to support the use of thin-film gel and liquid electrolytes on metallic surfaces. This allowed the collection of chemical information, left behind by the liquid electrolyte during evaporation, through a thin-film gel. The analysis of the gel electrolyte film confirmed the acidification on AA7075 and the alkalinization on CS1018 but also offered novel insights on their dependence on the galvanic current. The galvanic current was proportional to the initial NaCl concentration in the range of 0.01 to 0.06 M. However, due to continuous evaporation, the NaCl concentration increased, limiting oxygen diffusion and decreasing the galvanic current, especially for electrolytes exceeding 0.06 M. The galvanic current was determined by considering the dynamic evolution (caused by the evaporation of the electrolyte film) of both the thickness of the electrolyte and its concentration.

Enhancing microbial desalination cell performance for water desalination and wastewater treatment: experimental study and modelling of electrical energy production in open and closed‐circuit modes

AbstractBACKGROUNDMicrobial desalination cell (MDC) is a new technology in the use of electrical energy for water desalination and wastewater treatment.RESULTSOpen circuit (OC) and closed circuit (CC) modes were successfully simulated with initial TDS concentrations of 10 g/L and 10–15 g/L, respectively (an external resistance of only 150 Ω was applied for CC). After 160 h of operation, the maximum OC voltage, desalination efficiency and COD removal efficiency were 809 mV, 32.2% and 79.2%, respectively. The maximum voltage was also obtained when the external resistances were 150 Ω (423.4 and 438 mV) for the initial NaCl concentrations (10 and 15 g/L) in the central chamber, respectively. Moreover, the maximal desalting and COD removal efficiencies after 24 h run‐time were (30% and 28%) and (24% and 25%) for initial NaCl concentrations (10 or 15 g/L) in the central chamber, respectively. Maintaining pH (8.61, 7.01) to (7.85, 7.8) in anode and cathode chambers was studied. This research accurately depicted microbial desalination's efficiency in generating OC voltages and CC electrical energy via Box–Behnken Design Distribution (BBD). Investigated factors’ interactions (initial salt/COD concentrations, time) on CC system's energy efficiency. Resulted in peak productivity at (1.85 mW), OC reaching (1100 mV).CONCLUSIONFinally, the research paper gave exciting results in improving the efficiency of the microbial desalination cell to increase the ability to produce electrical energy and desalinate water. © 2023 Society of Chemical Industry (SCI).

Nano-silica from white silica sand functionalized with PANI-SDS (SiO2/PANI-SDS) as an adsorbent for the elimination of methylene blue from aqueous media

Natural resources including sand are one of the best approaches for treating dye-polluted wastewater. The SiO2/PANI-SDS nanocomposite was synthesized by self-assembly and intermolecular interaction. The physicochemical features of the SiO2/PANI-SDS nanocomposite were explored by FT-IR, XRD, SEM, TEM, EDX, and N2 adsorption–desorption techniques to be evaluated as an adsorbent for the MB. The surface area of the SiO2/PANI-SDS is 23.317 m2/g, the pore size is 0.036 cm3/g, and the pore radius is 1.91 nm. Batch kinetic studies at different initial adsorbate, adsorbent and NaCl concentrations, and temperatures showed excellent pseudo-second-order. Several isotherm models were applied to evaluate the MB adsorption on the SiO2/PANI-SDS nanocomposite. According to R2 values the isotherm models were fitted in the following order: Langmuir > Dubinin–Radushkevich (D–R) > Freundlich. The adsorption/desorption process showed good reusability of the SiO2/PANI-SDS nanocomposite.

Development of carboxymethyl cellulose-graphene oxide biobased composite for the removal of methylene blue cationic dye model contaminate from wastewater

Utilizing Glutaraldehyde crosslinked sodium carboxymethyl cellulose (CMC-GA) hydrogel and its nanographene oxide composite (CMC-GA-GOx), an effective carboxymethyl cellulose-graphene oxide biobased composites adsorbent was developed for the adsorption removal of methylene blue (MB) cationic dye contaminate from industrial wastewater. The CMC-GA-GOx composites developed were characterized using FTIR, RAMAN, TGA, SEM, and EDX analysis instruments. Through batch experiments, several variables affecting the removal of MB dye, including the biocomposites GO:CMC composition, adsorption time, pH and temperature, initial MB concentration, adsorbent dosage, and NaCl concentration, were investigated under different conditions. The maximum dye removal percentages ranged between 93 and 98%. They were obtained using biocomposites CMC-GA-GO102 with 20% GO weight percent, adsorption time 25 min, adsorption temperature 25 °C, MB concentrations 10–30 ppm, adsorption pH 7.0, and 0.2 g adsorbent dose. The experimental data of the adsorption process suit the Langmuir isotherm more closely with a maximal monolayer adsorption capacity of 76.92 mg/g. The adsorption process followed the kinetic model of pseudo-second order. The removal of MB was exothermic and spontaneous from a thermodynamic standpoint. In addition, thermodynamic results demonstrated that adsorption operates most effectively at low temperatures. Finally, the reusability of the developed CMC-GA-GO102 has been proved through 10 successive cycles where only 14% of the MB dye removal percentage was lost. These results suggest that the developed CMC-GA-GO102 composite may be an inexpensive and reusable adsorbent for removing organic cationic dyes from industrial wastewater.

Desalination performance of fabric-structured charged mosaic membrane prepared from poly(vinyl alcohol)-based charged fibers

Charged mosaic (CM) membranes were prepared from fabric structures using two types of poly(vinyl alcohol) (PVA)-based fibers. The fibers were fabricated using anionic and cationic block-type PVA, poly(vinyl alcohol-b-sodium styrene sulfonic acid), and poly(vinyl alcohol-b-vinylbenzyl trimethylammonium chloride). The fabrics were heat pressed to form a nonporous film and crosslinked with glutaraldehyde (GA) to produce fabric-structured CM membranes. Volume flux experiments indicated that the CM membrane exhibited negative osmosis, whereas the uncharged PVA membrane showed positive osmosis. The CM membrane made from the fabric exhibited sufficient mechanical strength for performing a piezodialysis experiment under a pressure of 0.3 MPa. The analytical results of piezodialysis experiments for the CM membrane indicated that the salt flux increased, whereas the water flux remained constant with an increasing initial NaCl concentration. Therefore, the salt-to-water flux ratio increased with increasing NaCl concentration. The CM membrane was desalinated with up to 1500 ppm of NaCl at a pressure of 0.3 MPa. Consequently, the fabricated CM membranes demonstrated the potential for desalinating low-salinity solutions.

Unexpected iron corrosion by excess sodium in two-dimensional Na–Cl crystals of abnormal stoichiometries at ambient conditions

At ambient conditions, we found salt crystals formed from unsaturated solutions on an iron surface; these salt crystals had abnormal stoichiometries (i.e. Na2Cl and Na3Cl), and these abnormal crystals with Cl:Na of 1/2–1/3 could enhance iron corrosion. Interestingly, we found that the ratio of abnormal crystals, Na2Cl or Na3Cl, with ordinary NaCl was relative to the initial NaCl concentration of the solution. Theoretical calculations suggest that this abnormal crystallisation behaviour is attributed to the different adsorption energy curves between Cl−–iron and Na+–iron, which not only promotes Na+ and Cl− adsorbing on the metallic surface to crystallise at unsaturated concentration but also induces the formation of abnormal stoichiometries of Na–Cl crystals for different kinetic adsorptionprocess. These abnormal crystals could also be observed on other metallic surfaces, such as copper. Our findings will help elucidate some fundamental physical and chemical views, including metal corrosion, crystallisation and electrochemical reactions.

Adaptive laboratory evolution to hypersaline conditions of lactic acid bacteria isolated from seaweed

Seaweed biomass has been proposed as a promising alternative carbon source for fermentation processes using microbial factories. However, the high salinity content of seaweed biomass is a limiting factor in large scale fermentation processes. To address this shortcoming, three bacterial species (Pediococcus pentosaceus, Lactobacillus plantarum, and Enterococcus faecium) were isolated from seaweed biomass and evolved to increasing concentrations of NaCl. Following the evolution period, P. pentosaceus reached a plateau at the initial NaCl concentration, whereas L. plantarum, and E. faecium showed a 1.29 and 1.75-fold increase in their salt tolerance, respectively. The impact that salt evolution had on lactic acid production using hypersaline seaweed hydrolysate was investigated. Salinity evolved L. plantarum produced 1.18-fold more lactic acid than the wild type, and salinity evolved E. faecium was able to produce lactic acid, while the wild type could not. No differences in lactic acid production were observed between the P. pentosaceus salinity evolved and wild type strains. Evolved lineages were analyzed for the molecular mechanisms underlying the observed phenotypes. Mutations were observed in genes affecting the ion balance in the cell, the composition of the cell membrane and proteins acting as regulators. This study demonstrates that bacterial isolates from saline niches are promising microbial factories for the fermentation of saline substrates, without the requirement of previous desalination steps, while preserving high final product yields.

Electrochemical Removal of Nitrogen Compounds from a Simulated Saline Wastewater.

In the last few years, many industrial sectors have generated and discharged large volumes of saline wastewater into the environment. In the present work, the electrochemical removal of nitrogen compounds from synthetic saline wastewater was investigated through a lab-scale experimental reactor. Experiments were carried out to examine the impacts of the operational parameters, such as electrolyte composition and concentration, applied current intensity, and initial ammoniacal nitrogen concentration, on the total nitrogen removal efficiency. Using NaCl as an electrolyte, the NTOT removal was higher than Na2SO4 and NaClO4; however, increasing the initial NaCl concentration over 250 mg·L-1 resulted in no benefits for the NTOT removal efficiency. A rise in the current intensity from 0.05 A to 0.15 A resulted in an improvement in NTOT removal. Nevertheless, a further increase to 0.25 A led to basically no enhancement of the efficiency. A lower initial ammoniacal nitrogen concentration resulted in higher removal efficiency. The highest NTOT removal (about 75%) was achieved after 90 min of treatment operating with a NaCl concentration of 250 mg·L-1 at an applied current intensity of 0.15 A and with an initial ammoniacal nitrogen concentration of 13 mg·L-1. The nitrogen degradation mechanism proposed assumes a series-parallel reaction system, with a first step in which NH4+ is in equilibrium with NH3. Moreover, the nitrogen molar balance showed that the main product of nitrogen oxidation was N2, but NO3- was also detected. Collectively, electrochemical treatment is a promising approach for the removal of nitrogen compounds from impacted saline wastewater.

Spinel LiMn2O4 as a Capacitive Deionization Electrode Material with High Desalination Capacity: Experiment and Simulation.

Capacitive deionization (CDI) is a newly developed desalination technology with low energy consumption and environmental friendliness. The surface area restricts the desalination capacities of traditional carbon-based CDI electrodes while battery materials emerge as CDI electrodes with high performances due to the larger electrochemical capacities, but suffer limited production of materials. LiMn2O4 is a massively-produced lithium-ion battery material with a stable spinel structure and a high theoretical specific capacity of 148 mAh·g-1, revealing a promising candidate for CDI electrode. Herein, we employed spinel LiMn2O4 as the cathode and activated carbon as the anode in the CDI cell with an anion exchange membrane to limit the movement of cations, thus, the lithium ions released from LiMn2O4 would attract the chloride ions and trigger the desalination process of the other side of the membrane. An ultrahigh deionization capacity of 159.49 mg·g-1 was obtained at 1.0 V with an initial salinity of 20 mM. The desalination capacity of the CDI cell at 1.0 V with 10 mM initial NaCl concentration was 91.04 mg·g-1, higher than that of the system with only carbon electrodes with and without the ion exchange membrane (39.88 mg·g-1 and 7.84 mg·g-1, respectively). In addition, the desalination results and mechanisms were further verified with the simulation of COMSOL Multiphysics.

Ultrahigh Content Boron and Nitrogen Codoped Hierarchically Porous Carbon Obtained from Biomass Byproduct Okara for Capacitive Deionization.

Capacitive deionization (CDI) is an environmentally friendly, energy efficient, and low cost water purification technique in comparison with other conventional techniques, and it has attracted considerable attention in recent years. Here, we use biomass byproduct okara as the starting material to fabricate a boron and nitrogen codoped hierarchically porous carbon (BNC) with ultrahigh heteroatom contents and abundant in-plane nanoholes for CDI application. With the interconnected hierarchical porous structure, the BNC not only exhibits a large surface area (647.0 m3 g-1) for the adsorption of ions but also offers abundant ion transport channels to access the entire internal surface. Meanwhile, the ultrahigh dopants' content of B (11.9 at%) and N (14.8 at%) further gives rise to the increased surface polarity and enhanced capacitance for BNC. Owing to these favorable properties, BNC exhibits top-level salt adsorption capacity (21.5 mg g-1) and charge efficiency (59.5%) at the initial NaCl concentration of ∼500 mg L-1. Moreover, we performed first-principle simulations to explore the different effects between N-doping and N,B-codoping on the capacitive property, which indicate that the boron and nitrogen codoping of carbon can largely increase the quantum capacitance over the double layer capacitance. The results of this work suggest a promising prospect for the BNC material in practical CDI application.

Nitrogen-doped hierarchical porous carbon obtained from silk cocoon for capacitive deionization

Capacitive deionization (CDI) has recently emerged as an alternative technology for water desalination. In this work, N-doped hierarchically porous carbon (NPC) has been synthesized using a sustainable and facile silk cocoon for its use as a high-performance CDI electrode. With an interconnected hierarchical porous structure, the NPC not only offers highly efficient ion transport pathways, but also provides a sufficient specific surface area (1315 m2·g−1) for the storage and adsorption of the ions. As a result, the NPC electrode affords a remarkable specific capacitance of 137.0 F·g−1 in 1.0 M NaCl solution, and enables an outstanding electrosorption capacity of 7.0 and 32.8 mg·g−1 with an initial NaCl concentration of 50.0 and 2500.0 mg·L−1, respectively. While, it also shows a high charge efficiency, salt adsorption rate, and cycle stability. The effectively N-doping and partly graphitizing of carbon in this porous material were regarded as the main reasons account for the satisfactory salt removing property. This study reveals that the NPC material exhibits a promising prospect for practical CDI application.

Architectures of flower-like MoS2 nanosheet coated N-doped carbon sphere electrode materials for enhanced capacitive deionization

The development of promising nanomaterials for capacitive deionization (CDI) is an emerging energy-efficient technology for water recovery and purification. Herein, the nanoarchitecture of deposition of molybdenum disulfide nanosheets onto N-doped carbon sphere (MoS2@NCS) has been successfully developed using hydrothermal processes for CDI applications. The morphological and fine structural analyses clearly indicate that the hexagonal structure of MoS2 nanosheets are homogeneously dispersed onto the 300-nm NCS to form the flower-like MoS2@NCS heterostructure. After calcination for 2 h at 800 °C, the MoS2@NCS exhibits a large specific surface area of 82 m2 g−1 and interconnected meso-macroporous channels for rapid ion and electron transfer, resulting in the superior electrochemical behaviors with the specific capacitance of 340 F g−1 at 5 A g−1 in 1 M Na2SO4 solution. Moreover, the electrosorption performance of MoS2@NCS-800 was investigated under different conditions in terms of initial NaCl concentration and voltage, and the superior specific electrosorption capacity of 59.9 mg g−1 is obtained at 2000 mg L−1 NaCl and applied voltage of 1.4 V. The experimental data is then well-fitted with the modified Donnan model, signifying that the electrosorption performance is highly dependent on the formation of electrical double layers and homogeneous potential distribution throughout the diffuse layer of the porous electrodes. The excellent cyclic durability of MoS2@NCS electrode is also highlighted after 100 electrosorption-desorption cycles. These results elaborate that MoS2@NCS composites are promising electrochemical materials for CDI application, which can open a pathway to design the 2D/3D hybrid nanoarchitectures as a highly potential material for green and sustainable water purification and ion removal in grey and salty waters.

Reusable Halophilic Bacteria Attached Cellulose Acetate Nanofiber Webs for Removal of Cr (VI) and Reactive Dye

Hexavalent Chromium (Cr (VI)) and Reactive Blue (RB) removal efficiencies of halotolerant Citricoccus sp. were examined for different parameters such as initial pH, contact time, temperature static/shaking, NaCl concentration, and different pollutant concentrations. In this research, Citricoccus sp. attached cellulose acetate (CA) nanofiber webs (NfW) were produced by electrospinning method to improve the removal yield even further. The Cr (VI) removal yield was calculated as 11.39 ± 0.002% for the pristine CA-NfW, whereas it was 39.19 ± 0.43% for bacteria attached CA-NfW. Therefore, the Cr (VI) removal capacities of bacteria attached CA-NfW were significantly higher than that of pristine CA-NfW. In addition, reusability tests revealed that bacteria attached CA-NfW can be used at least three successive times in decolorization and Cr (VI) removal steps. The decolorization rate of the RB and Cr (VI) removal yield was found to be 31.5 ± 0.2% and 5.63 ± 0.30%, respectively. These results are promising and therefore suggest that bacteria attached CA-NfW could be applicable for the removal of wastewater containing Cr (VI) and reactive dye due to their versatility and reusability.

Effect of Dough-Related Parameters on the Antimold Activity of Wickerhamomyces anomalus Strains and Mold-Free Shelf Life of Bread

The aim of the present study was to assess the antimold capacity of three Wickerhamomyces anomalus strains, both in vitro and in situ, and to identify the responsible volatile organic compounds. For that purpose, two substrates were applied; the former included brain heart infusion broth, adjusted to six initial pH values (3.5, 4.0, 4.5, 5.0, 5.5, 6.0) and supplemented with six different NaCl concentrations (0.0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%), while the latter was a liquid dough, fortified with the six aforementioned NaCl concentrations. After a 24 h incubation at 30 °C, the maximum antimold activity was quantified for all strains at 5120 AU/mL, obtained under different combinations of initial pH value and NaCl concentration. A total of twelve volatile compounds were detected; ethanol, ethyl acetate, isoamyl alcohol and isoamyl acetate were produced by all strains. On the contrary, butanoic acid-ethyl ester, acetic acid-butyl ester, ethyl caprylate, 3-methyl-butanoic acid, 2,4-di-tert-butyl-phenol, benzaldehyde, nonanal and octanal were occasionally produced. All compounds exhibited antimold activity; the lower MIC was observed for 2,4-di-tert-butyl-phenol and benzaldehyde (0.04 and 0.06 μL/mL of headspace, respectively), while the higher MIC was observed for butanoic acid-ethyl ester and ethyl caprylate (5.14 and 6.24 μL/mL of headspace, respectively). The experimental breads made with W. anomalus strains LQC 10353, 10346 and 10360 gained an additional period of 9, 10 and 30 days of mold-free shelf life, compared to the control made by commercially available baker’s yeast. Co-culture of the W. anomalus strains with baker’s yeast did not alter the shelf-life extension, indicating the suitability of these strains as adjunct cultures.

Electrocoagulation treatment of cork boiling wastewater

Electrocoagulation (EC) was studied as an alternative treatment for Cork Boiling Wastewater (CBW). EC was performed in a bench-scale reactor, using aluminum and stainless-steel electrodes and a sodium chloride solution was used to increase conductivity. Different values of current density, electric tension and electrolyte concentration were tested to assess treatment efficiency and operational costs. The tested procedures achieved removal efficiencies of 93.5%, 82.5%, 88.9% and 99.0% for chemical oxygen demand (COD), total carbon (TC), total nitrogen (TN) and total suspended solids (TSS), respectively, using an electric tension of 15 V. Some experiments after 20 min reached the maximum COD removal, showing that reduction of the operation time can be feasible to maximize cost-efficiency. The prediction of COD removal in a batch treatment based on initial NaCl concentration was investigated during a reactional period of 60 min, demonstrating that higher electrolyte concentrations promote COD removal. Langmuir, Jovanovic Monolayer and Multilayer models were applied and studied to predict the effect of current density and total aluminium mass on COD removal efficiency after 60 min of reaction. The Jovanovic Multilayer model predicted the operating performance for the removal of COD from CBW with higher accuracy when considering the current density. Operational costs for 60 min of electrocoagulation reactional periods have been determined in correlation with current density, in terms of cost per m3, €/COD removed, €/TN removed, €/TC removed, and €/TSS removed. Costs vary between 2.78 and 25.35 €/m3 with 27.6% and 93.8%, respectively. Electrode wear was higher than predicted, suggesting that about 14% of the mass loss should correspond to chemical dissolution. Results show that higher current density and electrolyte concentration reduces electrode wear time but increase overall pollutant removal.

Electrochemical study of a novel high-efficiency PbO2 anode based on a cerium-graphene oxide co-doping strategy: Electrodeposition mechanism, parameter optimization, and degradation pathways

A novel and efficient Ti/SnO2-Sb/PbO2-GO-Ce electrode was successfully fabricated based on the co-deposition of Ce ions and graphene oxide (GO) into β-PbO2 crystals and used as an anode for electrocatalytic oxidation of phenol. The electrodeposition mechanism, parameter optimization, mechanism analysis, and potential degradation pathways were discussed in depth. The co-doping of GO and Ce resulted in the high directional specificity of β(301), orderly and dense grain arrangement of PbO2 crystals. At the same time, the oxygen evolution potential, •OH generation capacity and lifetime were also improved. The effects of experimental parameters on phenol removal efficiency were evaluated, including the applied current density, electrode gap, supporting electrolyte, initial NaCl concentration, initial pH, and initial phenol concentration. Under the optimal conditions, the removal efficiency of phenol can reach 375.6 g m-2 h-1 for 20 min electrolysis, which is about 1.2 times that of the pure PbO2 electrode. The active oxygen species (•OH, ClO- and HClO) were important attributes to the degradation of phenol. Additionally, a potential degradation pathway for phenol was proposed. After 10 successive recycles, there was no significant difference of the electro-generated •OH, cell voltage and phenol removal rate, which confirms the stability and admirable reusability of Ti/SnO2-Sb/PbO2-GO-Ce electrode.

Characterization of β-glucosidase of Lactobacillus plantarum FSO1 and Candida pelliculosa L18 isolated from traditional fermented green olive

BackgroundOleuropein, the main bitter phenolic glucoside responsible for green olive bitterness, may be degraded by the β-glucosidase enzyme to release glucose and phenolic compounds. ResultsLactobacillus plantarum FSO1 and Candida pelliculosa L18 strains, isolated from natural fermented green olives, were tested for their β-glucosidase production and activity at different initial pH, NaCl concentrations, and temperature. The results showed that strains produced extracellular and induced β-glucosidase, with a molecular weight of 60 kD. The strains demonstrated their biodegradation capacity of oleuropein, associated with the accumulation of hydroxytyrosol and other phenolic compounds, resulting in antioxidant activity values significantly higher than that of ascorbic acid. The highest production value of β-glucosidase was 0.91 U/ml obtained at pH 5 and pH 6, respectively for L. plantarum FSO1 and C. pelliculosa L18. The increase of NaCl concentration, from 0 to 10% (w/v), inhibited the production of β-glucosidase for both strains. However, the β-glucosidase was activated with an increase of NaCl concentration, with a maximum activity obtained at 8% NaCl (w/v). The enzyme activity was optimal at pH 5 for both strains, while the optimum temperature was 45 °C for L. plantarum FSO1 and 35 °C for C. pelliculosa L18. ConclusionsL. plantarum FSO1 and C. pelliculosa L18 strains showed their ability to produce an extracellular and induced β-glucosidase enzyme with promising traits for application in the biological processing of table olives.