Reverse Osmosis Concentrate Research Articles

Modification of the distribution of humic acid complexations by introducing microbubbles to membrane distillation process for effective membrane fouling alleviation

Membrane fouling caused by inorganic ions and natural organic matters (NOMs) has been a severe issue in membrane distillation. Microbubble aeration (MB) is a promising technology to control membrane fouling. In this study, MB aeration was introduced to alleviate humic acid (HA) composited fouling during the treatment of simulative reverse osmosis concentrate (ROC) by vacuum membrane distillation (VMD). The objective of this work was to explore the HA fouling inhibiting effect by MB aeration and discuss its mechanism from the interfacial point of view. The results showed that VMD was effective for treating ROC, followed by a severe membrane fouling aggravated with the addition of 100 mg/L HA in feed solution, resulting in 45.7% decline of membrane flux. Analysis using the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory and zeta potential distribution of charged particles proved the coexistence of HA and inorganic cations (especially Ca2+), resulting in more serious membrane fouling. The introduction of MB aeration exhibited excellent alleviating effect on HA-inorganic salt fouling, with the normalized flux increased from 19.7% to 37.0%. The interfacial properties of MBs played an important role, which altered the zeta potential distributions of charged particles in HA solution, indicating that MBs adhere the HA complexations. Furthermore, this mitigating effect was limited at high inorganic cations concentration. Overall, MBs could change the potential characteristics of HA complexes, which also be used for other similar membrane fouling alleviation.

Reuse Rate Improvement of Wastewater Through Effective Removal and Recovery of High Concentration Phosphorus in Reverse Osmosis Concentrate and Food Waste Leachates

Reuse Rate Improvement of Wastewater Through Effective Removal and Recovery of High Concentration Phosphorus in Reverse Osmosis Concentrate and Food Waste Leachates

Multivariate optimization of characteristic parameters of continuous-flow system with a front buffer tank for industrial reverse osmosis concentrate treatment

Industrial reverse osmosis concentrate (ROC) was electrochemically oxidized using a continuous-flow system (CFS) with a front buffer tank. Multivariate optimization including Plackett-Burman (PBD) and central composite design based on response surface method (CCD-RSM) was implemented to investigate the effects of characteristic (e.g., recirculation ratio (R value), ratio of buffer tank and electrolytic zone (RV value)) and routine (e.g., current density (i), inflow linear velocity (v) and electrode spacing (d)) parameters. R, v values and current density significantly influenced chemical oxygen demand (COD) and NH4+−N removal and effluent active chlorine species (ACS) level, while electrode spacing and RV value had negligible effects. High chloride content of industrial ROC facilitated the generation of ACS and subsequent mass transfer, low hydraulic retention time (HRT) of electrolytic cell improved the mass transfer efficiency, and high HRT of buffer tank prolonged the reaction between the pollutants and oxidants. The significance levels of COD removal, energy efficiency, effluent ACS level and toxic byproduct level CCD-RSM models were validated by statistical test results, including higher F value than critical effect value, lower P value than 0.05, low deviation between predicted and observed values, and normal distribution of calculated residuals. The highest pollutant removal was achieved at a high R value, a high current density and a low v value; the highest energy efficiency was achieved at a high R, a low current density and a high v value; the lowest effluent ACS and toxic byproduct levels were achieved at a low R value, a low current density and a high v value. Following the multivariate optimization, the optimum parameters were decided to be v = 1.2 cm h−1, i ≥ 8 mA cm−2, d ≥ 4, RV = 10−20 and R = 1 to achieve better effluent quality (i.e., lower effluent pollutant, ACS and toxic byproduct levels).

Use of reverse osmosis concentrate for mitigating greenhouse gas emissions from pig slurry.

Due to the high global warming potential (GWP) in a short time scale (GWP100 = 28 vs. GWP20 = 86), mitigating CH4 emissions could have an early impact on reducing current global warming effects. The manure storage tank emits a significant amount of CH4, which can diminish the environmental benefit resulting from the anaerobic digestion of manure that can generate renewable energy. In the present study, we added the reverse osmosis concentrate (ROC) rich in salt to the pig slurry (PS) storage tank to reduce CH4 emissions. Simultaneously, pure NaCl was tested at the same concentration to compare and verify the performance of ROC addition. During 40 days of storage, 1.83 kg CH4/ton PS was emitted, which was reduced by 7-75% by the addition of ROC at 1-9 g Na+/L. This decrease was found to be more intensive than that found upon adding pure sodium, which was caused by the presence of sulfate rich in ROC, resulting in synergistic inhibition. The results of the microbial community and activity test showed that sodium directly inhibited methanogenic activity rather than acidogenic activity. In the subsequent biogas production from the stored PS, more CH4 was obtained by ROC addition due to the preservation of organic matter during storage. Overall, 51.2 kg CO2 eq./ton PS was emitted during the storage, while 8 kg CO2 eq./ton PS was reduced by biogas production in the case of control, resulting in a total of 43.2 kg CO2 eq./ton PS. This amount of greenhouse gas emissions was reduced by ROC addition at 5 g Na+/L by 22 and 65 kg CO2 eq./ton PS, considering GWP100 and GWP20 of CH4, respectively, where most of the reduction was achieved during the storage process. To the best of our knowledge, this was the first report using salty waste to reduce GHG emissions in a proper place, e.g., a manure storage tank.

Optimizing the removal of calcium and magnesium from synthetic reverse osmosis concentrate using functional polyketones: A combined experimental and machine learning approach

In this study, we synthesized functional polyketones (FPKs) for removing scaling ions (Ca2+ and Mg2+) from synthetic reverse osmosis concentrate (ROC) and optimized the adsorption processes using experimental and machine learning (ML) techniques, including gene expression programming (GEP) and multilayer perceptron (MLP) modeling. PK30 (a copolymer of ethylene and propylene with carbon monoxide) was reacted with four different amines, including 1,2-diaminopropane (DAP), 1-(2-aminoethyl) piperazine (AEP), butylamine (BA), and 1-(3-aminopropyl) imidazole (API), to produce FPKs. The effects of various factors, such as the amount of FPKs, synthetic ROC concentration, and pH, were investigated to optimize the removal of scaling ions from the synthetic ROC using novel GEP and MLP ML models. The experimental results revealed that Ca2+ and Mg2+ ions might be adsorbed primarily via the chelating mechanism. Increasing FPKs amounts and higher pH levels improved the adsorption process, with even low concentrations of FPKs demonstrating enhanced adsorption. The adsorption of the scaling ions followed the order API > AEP > BA > DAP, with removal percentages of 88.9, 87.3, 83.7, and 83.0 %, respectively. The MLP model outperformed the GEP model in optimizing Ca2+ and Mg2+ adsorption from the synthetic ROC and produced favorable results for all selected amines by determining the input-output relationship for the testing dataset with R2 = 0.806, 0.759, 0.760, and 0.878 for AEP, DAP, API, and BA, respectively. Overall, this study provides a viable solution for the pretreatment of ROC to remove scaling ions, which can improve the performance of zero liquid discharge systems by decreasing energy consumption.

Constructed Wetlands Using Treated Membrane Concentrate for Coastal Wetland Restoration and the Renewal of Multiple Ecosystem Services

The management of reverse osmosis concentrate (ROC) poses a challenge to utilities as it requires expensive disposal methods and advanced treatment in order to comply with regulations. This paper presents studies of natural treatment approaches, such as constructed wetlands (CWs), that have been tailored to treat ROC. Conceptually, with testing and planning, these wetlands could meet regulatory criteria before discharging to the surface water and achieving multiple benefits. Lessons learned from pilot studies of wetland treatment of ROC point to the potential benefits of designing full-scale wetlands for concentrate management. Studies have illustrated the ability of CWs to reduce the concentrations of metals and simultaneously remove nutrients to meet state standards for aquatic and wildlife designated uses. Nutrient removal processes include denitrification for nitrogen removal (possibly supplemented with Annamox reduction of NO3-N), labile carbon assimilation supporting oxidized nitrogen reduction, and phosphate-P uptake and precipitation. Because of the evaporative water loss, mass removal efficiencies were greater than concentration reductions. Studies illustrate how engineered wetlands help with the management of ROC produced from reclaimed water through reductions in concentration and volume for disposal through evapotranspiration. The associated creation of wildlife habitats and coastal wetland restoration could result in the renewal of multiple ecosystem services.

Effective and mechanistic insights into reverse osmosis concentrate of landfill leachate treatment using coagulation-catalytic ozonation-bioaugmentation-based AnMBR

Landfill leachate membrane concentrates containing high concentrations of organics pose a major threat to the environment, and efficient treatment methods are urgent issue. In this study, a coagulation-catalytic ozonation-bioaugmentation-based anaerobic membrane bioreactor (CCOB-AnMBR) process was applied to treat reverse osmosis concentrate (ROC) of landfill leachate. Compared with polyaluminum ferric chloride (PAFC) and prefrontal cortex (PFC), coagulation using polyferric sulfate (PFS) effectively removed refractory contaminants including macro molecular organics (MMOs), benzene ring compounds (BRCs), humic acid (HA), and fulvic acid (FvA) in ROC of landfill leachate, with average 78.3%, 53.5%, 34.7% and 34.3%, respectively. Catalytic ozonation with MnOx-CeOx-Al2O3 increased the biodegradability index by degrading refractory organic compounds, which facilitated subsequent biological treatment of ROC. The oxidation of mostly occurs at the solid–liquid interface and the presence of MnOx-CeOx-Al2O3 nanocatalyst enhanced ozone decay and increased generation of hydroxyl radical (•OH) and singlet oxygen (1O2) in ROC. In addition, bioaugmentation using recombinant genetically engineered Desulfovibrio vulgaris expressing Sat and dsrAB (rGEDEV-sds) promoted metabolism of sulfate by driving transfer sulfate from the environment into the cell and sulfate dissimilation reduction process. Bioaugmentation-based AnMBR (Bio-AnMBR) caused complete degradation of the total organic carbon (TOC), enhanced degradation of leachate pollutions, and decreased the concentration of sulfate in ROC. The macro molecular organics, refractory organic contaminants, the residual coagulation-resistant substances (CRS), and heavy metal were effectively degraded in the Bio-AnMBR system. Furthermore, CCOB-AnMBR exhibits high processing efficiency in the degradation of the contaminants in ROC of landfill leachate. Overall, this excellent performance proves the feasibility and elucidates the mechanism of CCOB-AnMBR process for the removal of contaminants in ROC of landfill leachate.

Removal of Organics with Ion-Exchange Resins (IEX) from Reverse Osmosis Concentrate.

Reverse osmosis concentrate (ROC) produced as the by-product of the reverse osmosis process consists of a high load of organics (macro and micro) that potentially cause eco-toxicological effects in the environment. Previous studies focused on the removal of such compounds using oxidation, adsorption, and membrane-based treatments. However, these methods were not always efficient and formed toxic by-products. The impact of ion-exchange resin (IEX) (Purolite®A502PS) was studied in a micro-filtration-IEX hybrid system to remove organics from ROC for varying doses of Purolite® A502PS (5-20 g/L) at a flux of 36 L/m2h. The purolite particles in the membrane reactor reduced membrane fouling, evidenced by the reduction of transmembrane pressure (TMP), by pre-adsorbing the organics, and by mechanically scouring the membrane. The dissolved organic carbon was reduced by 45-60%, out of which 48-81% of the hydrophilics were removed followed by the hydrophobics and low molecular weight compounds (LMWs). This was based on fluorescence excitation-emission matrix and liquid chromatography-organic carbon detection. Negatively charged and hydrophobic organic compounds were preferentially removed by resin. Long-term experiments with different daily replacements of resin are suggested to minimize the resin requirements and energy consumption.

Cholesterol Biosynthesis Inhibitor RO 48-8071 Suppresses Growth of Epithelial Ovarian Cancer Cells in Vitro and In Vivo.

Epithelial Ovarian Cancer (EOC) cells express enzymes in the cholesterol biosynthetic pathway, making this pathway an attractive therapeutic target for controlling ovarian cancer. Potent small molecule inhibitors of one biosynthetic enzyme, Oxidosqualene Cyclase (OSC), have been identified, and RO 48-8071 (4'-[6-(allylmethylamino)hexyloxy]-4-bromo-2'-fluorobenzophenone fumarate) (RO), has emerged as a useful chemotherapeutic agent for breast and prostate cancer. Cell viability assays were performed to determine effects of RO 48-8071 on growth of EOC cells. Aldehyde Dehydrogenase (ALDH) assay was conducted to determine the effects of drug on reducing stem cell like properties of EOC cells. Finally, xenograft studies were performed to assess the ability of RO 48-8071 to inhibit the growth of EOC cells in vivo. We found that short-term (24-48 h) administration of pharmacological doses of RO effectively reduced the viability of drug-resistant EOC cells (SK-OV-3 and OVCAR-3), as determined with sulforhodamine B colorimetric assays. In 7-day assays, nanomolar concentrations of RO effectively inhibited the growth of EOC cells. RO also suppressed ALDH activity, a marker of stem cells. Importantly, RO significantly suppressed growth of xenografts derived from EOC cells when given to mice intraperitoneally (20-40 mg kg-1 day-1) for 27 days once tumors reached 100 mm3 (controls: 336 + 60 mm3; treated: 171 + 20 mm3) with no toxicity to the experimental animals. Mechanistically, RO induced apoptosis in tumor cells in vivo as shown with immunohistochemistry. Cholesterol biosynthesis inhibitor RO 48-8071 is thus a novel and potent inhibitor of human EOC, including EOC stem cells.

Improvement of coal gasification reverse osmosis concentrate treatment by Cu-Co-Mn/AC catalytic ozonation.

Approximately 20% of concentrate will be produced from coal gasification wastewater after reverse osmosis treatment. The organic matter contained in the concentrate affects its evaporation crystallisation; therefore, the refractory organics must be removed. In this study, Cu-Co-Mn/AC catalytic ozonation was used to treat reverse osmosis concentrate (ROC). With the addition of the Cu-Co-Mn/AC catalyst, the production of ·OH increased by 82 μmol/L, thereby enhancing the ozonation performance. The pH, ozone dosage, and catalyst dosage all affected the catalytic ozonation performance. By constructing a response surface model, it was found that the catalyst dosage had the most significant effect on the catalytic ozonation performance. The predicted optimal reaction conditions were pH = 9.02, ozone dosage = 1.08 g/L, and catalyst dosage = 1.33 g/L, under which the chemical oxygen demand (COD) removal reached a maximum of 81.49%.

Performance of electrochemical treatment of refractory organic matter in printing and dyeing reverse osmosis concentrate

The printing and dyeing wastewater treatment process produces a reverse osmosis concentrate (ROC) that contains high organic matter content and requires proper treatment before discharge. Electrochemical oxidation was applied in this study to treat organic pollutants in the ROC. In addition, the concentration variation of phthalate esters (PAEs) in ROC was investigated. The results demonstrated that the electrochemical oxidation process could effectively reduce the organic content in ROC; the total organic carbon (TOC) removal efficiency reached 83.38% at pH 2.4 and a current density of 40 mA/cm2. Increasing the current density can markedly enhance the oxidation of the bulk organic matter (i.e., TOC, chemical oxygen demand (COD), UV254, and fluorescence). The effect of pH on the decomposition of organic materials was slightly less as than that of current density. The molecular weight (MW) distribution in the ROC indicated that the percentage of components larger than 5 kDa was approximately 10%, but decreased to 2.16% with persistent electrolysis. Further, 3D fluorescence spectroscopy suggests that the organic matter in ROC was mainly aromatic proteins (APⅡ) and soluble microbial products (SMP), which account for 25.78% and 51.39% of the total fluorescence, respectively. Notably, acidic conditions are more favorable for the breakdown of fluorescence, which is attributed to the higher oxidative capacity of·OH. The decomposition of PAEs was enhanced by lowering the pH, and degradation efficiency increased by 36.45% when the pH was lowered from 9.8 to 2.4. Qualitative analysis by gas chromatography-mass spectrometry (GC-MS) showed that the abundance of organic matter in the treated ROC was significantly decreased.

Application of partial ozonation on tank truck cleaning concentrate and the influence on biodegradability and ecotoxicity: a pilot-scale study.

This study investigates the pilot-scale ozone treatment of reverse osmosis concentrate (ROC), originating from variable tank truck cleaning wastewater. The influence of ozonation on short- and long-term biodegradation potential was examined through respirometry and Zahn-Wellens, respectively. Ecotoxicity was also examined for several concentrate batches and ozonation steps. Chemical oxidation through ozone had a beneficial effect on chemical oxygen demand removal, with a removal efficiency up to 56%. Formation of short-term biochemical oxygen demand (BODst) was induced for several, but not all batches, showing the potential of subsequent biological treatment of ozonated ROC. An increase in the inherent biodegradability through Zahn-Wellens was observed for all tested samples after ozonation, rising to a maximum of 68% after 3 hours of ozonation, highlighting the importance of sludge adaptation. Ecotoxicity, tested with Artemia franciscana and the saltwater algae P. tricornutum, showed initial decreases in algae inhibition after short ozonation periods. An increase in algae inhibition was, however, seen after prolonged ozonation for all tested ROC samples, pointing to the formation of ecotoxic by-products. Artemia showed no significant toxicity effects. When applying biological treatment through Zahn-Wellens, a decrease in ecotoxicity was observed for several samples, likely through biological oxidation of the produced degradation products.

Bipolar membrane electrodialysis for sustainable utilization of inorganic salts from the reverse osmosis concentration of real landfill leachate

Developing an effective resource utilization method for landfill leachate reverse osmosis concentrate (LLRC) remains a challenge because of the high concentrations of inorganic salts and refractory organic compounds. This study applied a bipolar membrane electrodialysis (BMED) to separate inorganic salts from real LLRC while simultaneously reclaiming inorganic acids and bases. The performance of BMED was affected by operating parameters, such as operating voltage, membrane surface flow velocity, and initial acid-base concentration. With optimized operating parameters, the reclaimed acid-base concentrations, desalination rate, and current efficiency were higher with less energy consumption. Ultimately, 0.41 mol/L acids and 0.40 mol/L bases were reclaimed from LLRC. The reclaimed acids contained 88 wt% HCl and 12 wt% HNO3. The reclaimed bases were 52 wt% NaOH and 45 wt% KOH. Furthermore, the concentrations of arsenic and heavy metals were low enough to safely utilize reclaimed products. The electromigration of organic compounds was controlled by protonation. After excluding the fixed costs, the net profit of 1 m3 LLRC treatment by BMED was $27.630, which showed remarkable economic feasibility. Our research offers a new strategy to realize sustainable utilization of inorganic salts from LLRC.

Substance flow analysis on the leachate DOM molecules along five typical membrane advanced treatment processes

The processes combining biological treatment with membrane separation technologies have been widely adopted for leachate treatment. However, dissolved organic matter (DOM) of leachate membrane concentrates generated from various membrane separation technologies has not been systematically investigated in field scale. Therefore, substance flow analysis based on DOM molecular information of leachate membrane concentrates from primary membrane systems (i.e. nanofiltration (NF) and reverse osmosis (RO)) and secondary membrane systems (i.e. disk-tube reverse osmosis (DTRO) and humic substance filtration system (HSF)) in five engineering-scale leachate treatment facilities, obtained via ultra-performance liquid chromatography coupled with hybrid quadrupole Orbitrap mass spectrometry, was given and simultaneously compared. In NF concentrates (NFC), 45.1–98.5% of DOM originated from raw leachate (L-DOM) was concentrated, showing poor biodegradability. The L-DOM interception characteristics of NFC-fed HSF were mainly based on volume reduction but concentration effect. L-DOM in RO concentrates (ROC) showed a higher proportion of peak intensity reduced components, accounting for 50.3–96.8%, and organic composition changes were more dependent on water quality characteristics than membrane types. ROC-fed DTRO intercepted 49.3–72.6% of L-DOM, but DTRO may be less effective at intercepting DOM molecules in landfill leachate with higher oxidation levels. Considering risks from feasible treatment technologies, the difficulty for the treatment of leachate membrane concentrates followed the order of DTRO concentrates > ROC > NFC. This study suggests that ROC-fed DTRO need to be controlled to avoid amplifying the treatment difficulty. Besides, treatment technologies for RO and DTRO concentrates with low-concentrated but refractory DOM and high salts should be explored.

Monitoring of experimental landfill cells with membrane concentrate infiltration: A systematic assessment of leachate quality and treatment performance

The present study investigates the impacts of reverse osmosis concentrate (ROC) infiltration on the leachate quality and treatment performance. Simulated landfill cells were constructed and monitored for 254 days. Integrated leachate samples were treated using a reverse osmosis (RO) system to assess changes in leachate quality on membrane fouling and effluent ecotoxicity. Our findings showed that concentrate infiltration increased the leachate's organic content and recalcitrance. The pollution parameters' median values were higher in leachates drained from cells that operated with ROC recirculation (i.e., 6729 vs 1367 mg L−1 [chemical oxygen demand, COD], 33.39 vs 17.39 cm−1 [absorbance at 254 nm, UV254]; p-value < 0.05). Membrane fouling resistance was 6-fold higher when the RO system was used to treat the methanogenic leachates generated by cells operating at ROC infiltration mode. The ecotoxicological assessment using Vibrio fischeri bacteria indicated that membrane concentrate recirculation increases leachate ecotoxicity and decreases its removal efficiency by RO treatment. The current research provides information to re-examine the recirculation practice of leachate concentrate streams. Recommendations and research prospects are drawn in this context.

Calcium carbonate scaling and seeding induced precipitation in FO treating textile reverse osmosis concentrate

Forward osmosis (FO) technology has been applied in the treatment and reclamation water from reverse osmosis concentrate. The performance of treating simulated textile reverse osmosis (sROC) was investigated with a focus upon the effect of calcium carbonate scaling and seeding induced precipitation on flux behavior. The effects of DS dilution & reverse salt flux (α), FS concentration & concentration polarization (β) and carbonate calcium scaling (γ) on flux decline were quantified based on the same water recovery at different DS (NaCl) concentration and FS salinity. The calcium carbonate scaling was found to contribute more to the flux decline when the FS salinity was 5000 ± 500 mg/L TDS at higher DS concentration. When the salinity of FS was increased to 10,000 ± 500 and 15,000 ± 500 mg/L TDS, the water flux was found higher under the situation of scaling than those of no scaling due to the fact that CaCO3 precipitation could inhibit the increase of osmosis pressure in FS in some degree. CaCO3 seeding induced precipitation in FO process promoted water flux and thus alleviated the calcium carbonate scaling on FO membrane. This work proposed a new view on the membrane scaling in FO process treating feed solution like reverse osmosis concentrate (ROC), and the seeding induced precipitation turned out to be an efficient strategy to alleviate calcium scaling in FO process and improve performance.

Preparation of Cu-Ce@γ-Al2O3 and Study on Catalytic Ozone Oxidation for the Treatment of RO Concentrate Water

In this paper, a high-efficiency and stable Cu-Ce@γ-Al2O3 catalyst was prepared by taking the reverse osmosis (RO) concentrated water of a sewage treatment plant as the treatment object and activated alumina as the carrier. The preparation factors that affected the catalytic activity of Cu-Ce@γ-Al2O3 were investigated. SEM, EDS, XRD, BET, XRF, and XPS techniques were applied to characterize the catalyst. Optimal working conditions, and degradation mechanism of RO concentrated water were researched. In comparison with the ozone oxidation alone, the Cu-Ce@γ-Al2O3 catalytic ozonation has more reactive groups, significantly improving the treatment effect. Characterization results show that Cu and Ce are successfully supported on the surface of the activated alumina support and mainly exist in the form of oxides (e.g., CuO and CeO2). The loading of metal led to a larger specific surface area and pore volume. The repeated use had an insignificant effect on the peaks of Cu2p and Ce3d energy spectra and caused a small loss of active components. Under these conditions, the removal rate of COD from RO concentrated water by Cu-Ce@γ-Al2O3 catalyst was 85.2%. The stability and salt tolerance of Cu-Ce@γ-Al2O3 catalysts were investigated by catalyst wear rate and repeated use times, respectively. The degradation of organic matter and residual tryptophan-like organic compounds were observed through UV absorption spectroscopy and 3D-EEM. Hydroxyl radicals participated in organic pollutants degradation. Finally, a multi-level-fuzzy analysis evaluation model was developed to quantitatively assess the catalytic ozone oxidation system of the Cu-Ce @γ-Al2O3 catalyst for the treatment of RO concentrated water.

Treatment of Simulated Radioactive Wastewater Using Reverse Osmosis and Membrane Distillation

With the rapid development of nuclear power, increasing attention has been paid to the treatment of low-level radioactive wastewater (LLRW). In this study, reverse osmosis (RO) and membrane distillation (MD) are used to treat LLRW containing Ce(III), U(VI), and Co(II). RO was used for the purification of LLRW. MD was used for further concentration of RO concentrate. The effect of the operating parameters, including operating pressure (0.6 to 1.4 MPa), feed pH (7 to 9), feed concentration (2 to 10 mg/L), feed temperature (50°C to 90°C), and feed flow rate (80 to 160 L/h) on the permeate flux and the rejection rate of the RO process and MD process was studied. The results demonstrate that it is very effective to use the RO process to treat LLRW containing Ce(III), U(VI), and Co(II), with the rejection rates of Ce(III), U(VI), and Co(II) higher than 99.97%, 99.98%, and 99.35%, respectively. The operating pressure has a significant effect on the permeate flux in the RO process. The permeate flux increases from 9.84 to 23.03 L/m2·h when the operating pressure increases from 0.6 to 1.4 MPa. The feed pH has an apparent influence on nuclide rejection. At the feed pH = 9, the rejection rates of Ce(III), U(VI), and Co(II) by the RO process can reach 99.99%, 99.99%, and 99.79%, respectively. MD can reject almost all the nuclides in the RO concentrate, with rejection rates consistently higher than 99.98%. Increasing the feed temperature and feed flow rate can result in a significant increase in the permeate flux, but has almost no effect on nuclide rejection in the MD process.

A Comprehensive Study of the Electrochemical Oxidation of Diclofenac Sodium in Reverse-Osmosis Concentrate: Analysis, Reaction Kinetics, and the Effect of Electrolyte Composition

A Comprehensive Study of the Electrochemical Oxidation of Diclofenac Sodium in Reverse-Osmosis Concentrate: Analysis, Reaction Kinetics, and the Effect of Electrolyte Composition

Boron Removal from Reverse Osmosis Permeate Using an Electrosorption Process: Feasibility, Kinetics, and Mechanism.

Boron is present in the form of boric acid (B(OH)3 or H3BO3) in seawater, geothermal waters, and some industrial wastewaters but is toxic at elevated concentrations to both plants and humans. Effective removal of boron from solutions at circumneutral pH by existing technologies such as reverse osmosis is constrained by high energy consumption and low removal efficiency. In this work, we present an asymmetric, membrane-containing flow-by electrosorption system for boron removal. Upon charging, the catholyte pH rapidly increases to above ∼10.7 as a result of water electrolysis and other Faradaic reactions with resultant deprotonation of boric acid to form B(OH)4- and subsequent removal from solution by electrosorption to the anode. Results also show that the asymmetric flow-by electrosorption system is capable of treating feed streams with high concentrations of boron and RO permeate containing multiple competing ionic species. On the basis of the experimental results obtained, a mathematical model has been developed that adequately describes the kinetics and mechanism of boron removal by the asymmetric electrosorption system. Overall, this study not only provides new insights into boron removal mechanisms by electrosorption but also opens up a new pathway to eliminate amphoteric pollutants from contaminated source waters.