Decrease In Removal Efficiency Research Articles

Application of Fe-RGO for the removal of dyes by catalytic ozonation process.

Due to continuous industrialization, the discharge of hazardous dyes has enormously disrupted the ecosystem causing environmental problems. Due to the stable recalcitrant nature of dyes, advanced catalytic ozonation processes with the latest catalyst are under investigation. Fe-RGO is an effective oxidation catalyst, and the metal loaded platform provides enhanced catalytic performance. This study aims to investigate the effectiveness of Fe-RGO/O3 process for the removal of dyes. In the current research, the application of iron-coated reduced graphene oxide (Fe-RGO) was studied as a catalyst in the heterogeneous catalytic ozonation process to remove dyes. Methylene blue (MB) was selected as a model pollutant. RGO was prepared using the improved Hummers method and was coated with iron (Fe) implying the impregnation method. The FTIR, SEM-EDX, XRD, and BET analyses of RG and Fe-RGO were performed to characterize the catalyst. The effect of various parameters such as pH (3-10), catalyst dose (0.01-0.04g), and radical scavengers (NaHCO3, NaCl) on removal efficiency was elucidated. The result revealed an excellent catalytic efficiency of Fe-RGO in the ozonation process. At optimum conditions, 96% removal efficiency was achieved in catalytic ozonation at pH 7 with a catalyst dose of 0.02g and ozone dose 0.5mg/min, after 10min. Interestingly, a slight decrease in removal efficiency was observed in the catalytic ozonation process in hydroxyl radical scavengers (NaCl and NaHCO3), which makes the proposed catalyst more applicable in real conditions. Therefore, it is concluded that Fe-RGO can be used as an excellent catalyst for the removal of dyes in real conditions where radical scavengers may be present in a significant amount.

Assessment of alkalinity on the adsorption of cadmium ion using KOH-activated carbon from Sesame stem

The increase alkalinity on the adsorption of cd2+ using KOH-activated carbon from Sesame stem was studied. Determination of metal ion in solution shows adsorption capacities of 86.68 % for KOH-AC at saturated state. Effect of metal ion concentration shows that, Removal efficiency of Cd2+ by KOH-AC increases with increasing presence of the adsorbate due to the availability of adsorption sites on the activated carbon. Increase acidity general favors the adsorption. The effect of pH shows that the adsorption of cadmium ions increases with increasing acidity between the pH of 7.5 to 6. However, as the Cd2+ concentration becomes exceedingly high, the removal efficiency decreases. A general observation was that before equilibrium, there is rise in the removal efficiency of Cd2+ by KOH-AC with increasing contact time which is universally true for good adsorbents. Effect of metal ionic strength shows that activated carbon adsorption decrease with increase in ionic strength in any acidic medium.

Analysis of 1H-benzotriazole removal efficiency from wastewater in individual process phases of a sequencing batch reactor SBR

The research focused on a very dangerous and commonly used compound which has carcinogenic and mutagenic impact on living organisms. 1H-benzotriazole (1H-BTR) is used as a corrosion inhibitor for installations in industrial plants, in the production of biocides, detergents, drugs, tires, rubber, in refrigeration systems and de-icing substances, while its derivates are UV stabilizers in plastics, paints, films and sunscreens. It is also an additive in petroleum products (lubricants, hydraulic fluids). The paper presents quantitative changes of 1H-BTR after sequencing batch reactor (SBR) process. The studies have been carried out for 411 cycles of SBR during which concentration of 1H-BTR was changed in the range of 50–1000 μg L−1. SBR operating cycle consisted of 6 phases: filling (dilution-40 min), mixing I (dephospatation-20 min), aeration with stirring (nitrification and oxidation of organic compounds-300 min), mixing II (denitrification-30 or 60 min), settling and decantation (separation-40 min), downtime (90 or 60 min). The technological parameters of the activated sludge (sludge volume index, solids and hydraulic retention time) were as similar as possible to those maintained in the real wastewater treatment plant (WWTP). Mixed liquor suspended solids concentration was 3.50 kg m−3. Conducted studies showed that industrial wastewater containing 1H-BTR can be effectively treated in SBR. The conducted studies showed that removal of 1H-BTR with more than 80% efficiency is possible at effluent concentrations not exceeding 200 μg L−1. Higher concentrations of 1H-BTR in wastewater lead to a sharp decrease in removal efficiency. The lowest removal efficiency (56.6%) was recorded at the initial 1H-BTR concentration of 100 μg L−1. On the other hand, the highest efficiency (88.2%) at the initial concentration of 1000 μg L−1. The concentration of 1H-BTR in treated wastewater was 1.1 μg L−1 in the control reactor and from 7.2 to 434.0 μg L−1 for an initial concentration from 50 to 1000 μg L−1, respectively. The aeration phase was superior in terms of 1H-BTR removal, regardless of the benzotriazole doze in the raw wastewater. In the anaerobic mixing phases I and II in the SBR, the decomposition of the 1H-BTR was 5.3 and 4.9 times slower, respectively, compared to aerobic conditions.

Recovery of cobalt from spent lithium ion batteries utilizing surface modified graphene oxide

Metal content present in the spent lithium ion batteries (LIBs) make their recycling vital for resources conservation and environmental sustainability. Cobalt, grouped among critical, valuable and strategic metals, is the basic part of the LIBs cathode and defines its recycling economic capacity. In the present work, an attempt has been made to develop an efficient hydrometallurgical technique based on solid phase extraction method for the recovery of cobalt from leach solution of waste LIBs. An adsorbent was synthesized by diazotization of p-phenylenediamine modified graphene oxide (GO-PPDA) sheets with disodium 1-nitroso-2-naphthol-3-6-disulphonate (nitroso R-salt, NRS) in one pot process of Mill's reaction. Maximum retention of cobalt (99.9%) was achieved at pH 5.5–6.5. Adsorption kinetics favour complexation as a separation mechanism following second order kinetics model with R2 value of 0.9999 with sample flow rate of 1.5 mL/min. Langmuir isothermal model (R2 = 0.998) also confirm monolayer chemisorption mechanism with 29.7 mg/g adsorption capacity. The two-step elution mechanism enables us to achieve 99.5% extraction efficiency with ~98% purity. The chelating adsorbent was found reasonably stable even after the 30th cycle of adsorption and desorption with <2% decrease in removal efficiency. The results show that the proposed adsorbent is successful in terms of selectivity, reusability, analytical merit and stability.

Facile preparation of floatable carboxymethyl cellulose-based composite hydrogel for efficient removal of organic dyes

Hydrogels have become efficient adsorbents in treatment of organic dyes from wastewater. However, the drawback of difficulty in separation and collection limited their applications. Herein, a series of floatable polyacrylamide/carboxymethyl cellulose‑copper sulfide (PAM/CMC-CuS) hydrogels were designed. The PAM/CMC-CuS hydrogel could not only be easily collected from the wastewater, but also selectively adsorb cationic dyes (Rhodamine B (RhB) and Neutral red (NR)) from the mixed solutions with different oppositely charged dyes. PAM/CMC-CuS hydrogel exhibited faster adsorption rate and higher adsorption capacity than that of PAM/CMC hydrogel. And the adsorption kinetic data were well described by pseudo-second-order model and adsorption isotherm data fitted well with Langmuir equation. Besides, PAM/CMC-CuS hydrogel exhibited excellent reusability and stability that no apparent decrease in removal efficiency was observed after five cycles. Altogether, the good adsorption capacity, floatability, selectivity and reusability will promote the PAM/CMC-CuS hydrogel to be a superior adsorbent in removal cationic dye from wastewater.

Effects of Vallisneria natans on H2S and S2− releases in black-odorous waterbody under additional nitrate: Comprehensive performance and microbial community structure

Releases of hydrogen sulphide (H2S) and sulphur ions (S2−) through sulphate reduction in black-odorous waterbody is a great environmental health concern. Aquatic planting for blackening and odour controls has received great attention in research and practice. Nitrate concentration in black-odorous waterbody can vary significantly but little is known about the responses of aquatic plants on H2S and S2− releases under different nitrate levels. This controlled laboratory study explored the changes of H2S and S2− releases in simulated black-odorous waterbody planted with Vallisneria natans and artificial plants (control). V. natans growth was stimulated by additional nitrate (6.6 mg/L NO3−-N), resulting in an increase of dissolved oxygen (DO) and pH in overlying water and an 11.0% decrease in removal efficiency of chemical oxygen demand (COD). At relatively low nitrate level (i.e., 2.0 mg/L NO3−-N in the absence of additional nitrate), V. natans after the 48th day inhibited H2S and S2− releases by 81.5% and 66.8%, respectively, and their inhibition efficiencies were improved to 95.7% and 98.8% by the presence of additional nitrate. Additional nitrate reduced the relative abundance of sulphate-reducing bacteria (SRB) in the sediments while increased the relative abundance of sulphur-oxidizing bacteria (SOB) and nitrate-reducing sulphur-oxidizing bacteria (NR-SOB) in the leaf biofilms of V. natans and artificial plants. Genus compositions in leaf biofilms showed host specificity. Pearson correlation analysis showed that DO, pH, and nitrate concentration had a positive correlation with the relative abundance of SOB (Aeromonas) and NR-SOB (Hydrogenophaga), while were negatively correlated with the relative abundance of SRB (MSBL7). These results indicated that V. natans under additional nitrate altered microbial community to be unfavourable for H2S and S2− releases. This study clarified the inhibition of H2S and S2− releases by aquatic planting under additional nitrate and provided theoretical basis for improving black-odorous waterbody restoration technology.

Digging deep into a GAC filter – Temporal and spatial profiling of adsorbed organic micropollutants

A large pilot-scale granular activated carbon (GAC) filter was operated downstream in a full-scale wastewater treatment plant to remove organic micropollutants. To describe the spatial and temporal developments of micropollutant adsorption profiles in the GAC filter, micropollutants were extracted from GAC media taken at various filter depths and number of treated bed volumes. At a low number of treated bed volumes (2600 BVs), most micropollutants were adsorbed in the top layers of the filter. At increasing number of treated bed volumes (7300–15,500 BVs), the adsorption front for micropollutants progressed through the filter bed at varying rates, with sulfamethoxazole, fluconazole, and PFOS reaching the bottom layer before carbamazepine and other well-adsorbing micropollutants, such as propranolol and citalopram. Higher amounts of adsorbed micropollutants in the bottom layer of the filter bed resulted in decreased removal efficiencies in the treated wastewater. Mass estimations indicated biodegradation for certain micropollutants, such as naproxen, diclofenac, and sulfamethoxazole. A temporary increase in the concentration of the insecticide imidacloprid could be detected in the filter indicating that extraction of adsorbed micropollutants could provide an opportunity for backtracking of loading patterns.

Optimization of Pb2+, Cd2+, Ni2+ and Ba2+ adsorption onto light expanded clay aggregate (LECA)

The possibility of Pb2+, Cd2+, Ni2+ and Ba2+ ions removal from aqueous solution using light expanded clay aggregate (LECA) was investigated in this work. The central composite design (CCD) in response surface methodology (RSM) was used to optimize the operating parameters (adsorbent granulometry, absorption time and initial metal ions concentration) to reach the maximum ions removal in single and multi-elemental solutions. After optimization, the results shows that the removal efficiency decrease following the ion sequence Pb2+ &gt; Ba2+ &gt; Cd2+ &gt; Ni2+ ions. The better efficiency (~95%) is observed for the Pb2+. The Langmuir and Freundlich isotherm models were applied to the equilibrium data at room temperature. The results revealed that data on LECA was very well fitted with Langmuir equations. The real interest of this work is to demonstrate that a simple material such as LECA can be used to remove extremely small levels of toxic metals, such as those found in drinking water. So our results could be the starting point for the development of a low-cost filtration system to remove toxic metals.

Adsorption characteristics of the carbonaceous adsorbents for organic compounds in a model exhaust gas from thermal treatment processing

ABSTRACT This study investigated the adsorption characteristics of the carbonaceous adsorbents for organic compounds in gas to gain technical knowledge useful for the appropriate operation and management of the incineration plants and industrial heat treatment facilities. The experiments in the study were performed using a dynamic method, employing a small column packed with test adsorbent, into which flowed the model gas, primarily over a temperature range of 150°C to 190°C. Three activated carbon materials and an activated coke were used, with specific surface areas ranging from 250 to 1,100 m2/g-adsorbent. Organic components in the gas were produced and supplied at a concentration of tens of mg/m3, and gaseous mercury was supplied at a concentration of around 100 μg/m3. The experimental results showed the following: 1) The adsorption capacity of every carbonaceous material for organic vapor decreased with increasing temperature, with roughly a three-fold difference in the capacity, between 150°C and 190°C in the dry gas. The equilibrium adsorption amount of benzene could be estimated based on the specific surface area of the adsorbent. 2) Gas moisture reduced the equilibrium adsorption amount of adsorbates by about half. 3) The estimation of the treatment performance for actual adsorption processing suggested the possibility of decreased removal efficiency at higher temperatures above 175°C. Overall, the precise process design should be made based on future practical studies. Implications: Adsorptive characteristics of activated carbon materials were examined for benzene and chlorobenzene in gas within the temperature range of 150°C to 190°C. The adsorption amount of benzene at high temperature and low concentration range below 20 ppm was in the range of 103 to 104 mg/kg-adsorbent. There was a clear difference between the adsorption parameters of activated carbon and coke for the benzene adsorption, depending on their specific surface area values and other factors.

A mixed agro-waste based biofilter for the removal of methyl ethyl ketone: Kinetics and modeling

Biofiltration has grown worldwide, as an inexpensive and consistent air pollution control technology for the elimination of numerous organic compounds. In this work, the biofiltration of methyl ethyl ketone (MEK) has been studied. The agro-wastes namely pressmud and cornstack are mixed and used as packing materials for the removal of MEK. The performance of the biofilter has been explored over 200 days. Experiments are carried out in four periods. In every period, the biofiltration of pollutants is performed for various inlet concentrations (IC) of MEK (0.2–1.2 g m−3) and gas flow rates (GFR) (0.03 m3 h−1 to 0.12 m3 h−1). The biofilter performances are investigated by their removal rates, elimination capacity, temperature, pressure drop, carbon dioxide production, and variation of bed height at the time of operations. For the IC of 0.2 ± 10% g m−3 and GFR of 0.03 m3 h−1, the removal efficiency (RE) of MEK is 97% using the mixture of cornstack (80%) and pressmud (20%). The MEK removal efficiency decreases, when the cornstack ratio increases. The maximum RE is obtained at the IC of 1.2 g m−3 and GFR of 0.12 m3 h−1 for all the tested conditions. The pressure drop (PD) is also measured for all the operating conditions. It is found that the PD rises with an increase in height. The temperature is monitored throughout the biofiltration process. It is observed that an increase in RE leads to a rise in temperature in the biofilter. SEM images confirm the growth of microbes on the packing material. The kinetics of removal of MEK is investigated by using Ottengraf–van den Oever model.

A statistical modeling-optimization approach for photocatalytic degradation of diflouro triazole acetophenone using Ag-Fe co-doped TiO2: response surface methodology.

In this research, the performance of Ag-Fe co-doped TiO2 (Ag-Fe CT) nanophotocatalyst for degradation of diflouro triazole acetophenone (DTA) from aqueous solutions under solar and UV radiations was compared. The novel photocatalyst was synthesized using a sol-gel method with varying Ti to Ag mole ratio (10, 25, 30, 40, 55). Synthetic wastewater was prepared from diflouro triazole acetophenone (DTA concentration 8g/L and COD = 75,000mg/L). Ag-Fe CT 30 photocatalyst has shown maximum COD removal efficiency for solar and UV irradiation. Ag-Fe CT 30 photocatalyst was able to absorb visible and UV radiations. Recyclability test proved that Ag-Fe CT 30 can be reused 3 times effectively for a not significant decrease in COD removal efficiency. A response surface methodology (RSM) was used to study the single and combined effects of pH, photocatalyst dose, and Ti to Ag mole ratio parameters. Model showing relation of parameters with COD reduction efficiency has been developed and optimization has been carried out for solar and UV radiations. Results revealed that the optimal conditions for DTA removal were initial pH 5, photocatalyst dose of 3g/L, and Ti to Ag mole ratio of 30. Maximum COD removal efficiency of 76% and 86% was observed under solar and UV radiations, respectively. This study would be useful for the removal of non-biodegradable organics from high-strength COD effluent in an economical and eco-friendly way.

Feasibility Study of Using graphene Oxide/silica Gel Nanocomposite Prepared by Sol-gel Method for Removing Malachite Green from Aqueous Solutions: Optimization, Kinetic, and Isotherm Studies

The main objective of this work was to evaluate the feasibility of the application of GO/Na2SiO3 nanocomposite as highly efficient adsorbent for the removal of malachite green as a cationic dye from aqueous solutions. To do so, first the synthesized nanosorbent was characterized via FTIR, SEM, TEM and XRD techniques. Surface area and pore mean size of above mentioned nanocomposite were determined using BET technique. Also, some important parameters affecting the efficiency of the absorption of malachite green, such as pH, adsorbent dosage, contact time, primary concentration of dye and salt effect were optimized. The malachite green (water-soluble) dye was analyzed at a maximum wavelength of 618 nm. The optimal conditions for removal of malachite green from aqueous solution included a 20 mg l-1 initial concentration with 25 mg adsorbent at pH 7, and adsorption equilibrium was achieved within 5 min. Kinetic studies confirmed that dye adsorption process followed pseudo-second order kinetic models (R2 = 0.9999) and adsorption equilibrium data showed good correlation with Freundlich isotherm (R2=0.9982 at 298 K). Thermodynamic analysis indicates that the adsorption process is spontaneous and exothermic in nature. In addition, the experimental data obtained from reusability studies showed that the prepared adsorbent could be used in up to six adsorption-desorption cycles without significant decrease in removal efficiency.

Magnetic bimetallic Fe, Ce-embedded N-enriched porous biochar for peroxymonosulfate activation in metronidazole degradation: Applications, mechanism insight and toxicity evaluation

A novel honeycomb-like porous Fe-Ce@N-BC composite was synthesized as an effective and green PMS activator for MNZ removal through radical and non-radical processes. • Bimetallic Fe- and Ce-embedded N-enriched porous biochar (Fe-Ce@N-BC) was prepared. • Pyridinic N and C O on the surface of Fe-Ce@N-BC facilitate the PMS activation. • Both radical and non-radical processes contribute to the oxidation reaction. • Fe-Ce@N-BC exhibits a superior activity in MNZ degradation in seawater and effluent. • Animal cell test reveals low cytotoxicity of both the intermediates and the material. Bimetallic Fe- and Ce-embedded N-enriched porous biochar (Fe-Ce@N-BC) was synthesized to activate peroxymonosulfate (PMS) for metronidazole (MNZ) removal. 97.5% decay of MNZ was achieved within 60 min in Fe-Ce@N-BC/PMS system. The kinetic reaction rate constant of the Fe-Ce@N-BC/PMS system (0.0566 min −1 ) was 10.5 times higher than that of the BC/PMS system (0.0054 min −1 ). The highly dispersed Fe-Ce oxide nanocrystals serve as PMS activation centers, while the addition of nitrogen source increases the surface area and porosity of biochar, as well as enhances the PMS activation performance. It is noteworthy that graphitic N and C O groups in biochar facilitates the PMS activation via a nonradical pathway and the Fe 2+ /Fe 3+ and Ce 3+ /Ce 4+ participate in the radical pathway. The presence of anion ions of SO 4 2− can promote the MNZ degradation process, while HCO 3 – and Cl − ions suppress the MNZ removal. The MNZ removal using Fe-Ce@N-BC in salty media behavior similarly with that in DDI water, while the decreased removal efficiency in real effluent could be mitigated by prolonging the reaction time. Finally, the degradation intermediate products of MNZ were identified and the pathway was proposed according to LC-MS analysis. The relatively low cytotoxicity of the Fe@Ce/N-BC evaluated by animal cell (A375) and toxicity evolution of MNZ intermediate products strongly suggest huge potential of utilization of the catalyst for aquatic environmental remediation.

Regenerable Mg/Fe bimetallic hydroxide for remarkable removal of low-concentration norfloxacin from aqueous solution

The widespread existence of antibiotics in aquatic environments has gained much concern due to their non-biodegradability and eco-toxicity, which would easily destroy the ecological balance. In this work, the synthesized Mg/Fe layered bimetallic hydroxides (Mg/Fe LDHs) was first used to adsorb low concentration norfloxacin (NOR) antibiotics in water. It was found that the LDH adsorbent with a Mg/Fe molar ratio of 5:1 (MF5:1) exhibited superior adsorption properties for the removal of low concentration (20 mg·L-1) of Norfloxacin (NOR). The adsorption capacity could reach to ~ 97.07 mg·g-1 at neutral pH. Kinetic fitting shows that it could be well described by Pseudo-second-order models, indicating that chemical adsorption dominants the process. Also, the isothermal adsorption data could be well fitted by Freundlich isotherm model, which suggests a multilayer adsorption process. The adsorbent has good properties of salt resistance with ~ 5% and 30% decrease of removal efficiencies in 0.1 mol·L-1 KCl and CaCl2 solution, respectively. By contrasting the structural variation of the adsorbent before and after adsorption, it could be inferred that coordination and hydrogen bonding rather than electrostatic interaction might be the main forces between NOR and Mg/Fe5:1 nanocrystal. In addition, the recover of the adsorbent could be easily achieved by pyrolysis and rehydration circle with little decrease of adsorption property. Our finding suggests that Mg/Fe LDHs can be severed as a promising candidate for the removal of antibiotics, especially for the low concentrations of NOR.

The effect of salinity on ammonium-assimilating biosystems in hypersaline wastewater treatment

The ammonium-assimilating biosystem is a promising solution to improve the susceptible biological nitrogen removal (BNR) and to achieve nitrogen recovery in saline wastewater treatment. However, the treatment performance and functional stability of ammonium-assimilating biosystems have not been fully illuminated in hypersaline wastewater. In this study, although the dramatic decrease of removal efficiency of NH4+-N and PO43−-P was observed in ammonium-assimilating biosystems under the salinity from 3% to 7%, the direction of nitrogen conversions through assimilation was insusceptible to high salinity. The extremely low concentrations of nitrite and nitrate accumulation and abundances of nitrification functional genes confirmed that the process of nitrification was negligible in all biosystems. Ammonium-assimilating biosystems maintained robustness and functional stability in hypersaline wastewater. The increase of salinity stimulated the production of EPS and changed the microbial community by enriching Proteobacteria and halophilic genera. We anticipate that the ammonium-assimilating biosystem could be a promising strategy for hypersaline wastewater treatment and future practical applications.

Minimizing excess sludge production under synergistic effect of diatomite and uncoupling agent 2,4-dinitrophenol: An in-depth study

Excess sludge production is one of the major challenges in the wastewater treatment plants worldwide. The main solution is to reduce the burden of sludge by lowering its production. In this study, the strategies for sludge reduction using uncoupler DNP (2,4-dinitrophenol) with diatomite or diatomaceous earth (natural sedimentary rock) are evaluated for practical application using cost analysis and assessment of environmental impact. There was a decrease in average removal efficiency of chemical oxygen demand (COD), ammonia nitrogen (NH 4 + -N) and total nitrogen (TN) of 7–30%, 20% and 44%, respectively. The sludge volume index (SVI) was 80–120 mL/g while the sludge activity increased by 21%. By cost analysis and comparison of the various parameters, it was determined that the optimal dosage of DNP was 6 mg/L. The problem of poor effluent quality and sludge performance caused by the addition of DNP alone was solved by the collaborative addition of DNP and diatomite. Diatomite can absorb the coupling agent like a carrier to form a compound uncoupling agent. Diatomite easily aggregate and mixed with sludge micelle particles. DNP will slowly release and dissolve into sludge micelles after they are mixed, resulting in higher DNP concentration in sludge micelles. A synergistic effect of DNP and diatomite on sludge reduction showed increase in removal efficiency COD, NH 4 + -N and TN of 13.35%, 18.6% and 26.58%, respectively. SVI was decreased by 13%. A sewage treatment of 1 m 3 can still save sludge treatment cost by $ 0.0084. Comparing the synergistic dose, observed sludge yields (Yobs) decreased by 28.28% (48 mg of DNP with 0.4 g of diatomite; one-time dosage per two-days) and 21% (24 mg of DNP with 0.2 g of diatomite; once a day dosage). The sludge activity also increased. By orthogonal test results, the optimum environmental influence factors for the treatment system are set to 25 °C and pH 7.

A Study on Performance and Reusability of Certified and Uncertified Face Masks

In this study, the performance (particle removal efficiency and breathing resistance) of several commercially available face masks (KF80-certified electrostatic and nanofiber filter masks, and an uncertified mask) was evaluated, along with their filter structure and composition. Also, the effects of the relative humidity (RH) of incoming air, of water and alcohol exposure, and of reuse, on the performance of face masks were examined. Monodisperse and polydisperse sodium chloride particles were used as test aerosols. Except for the uncertified mask filter, PM2.5 removal efficiency was > 90%. The nanofiber filter mask had the highest quality factor due to its low pressure drop and high removal efficiency, and densely packed nanofiber pore structure, and significant amounts of fluorine, carbon and oxygen. The removal efficiency of the KF80-certified mask was barely affected by the higher RH of incoming air. When the mask filters were soaked in water, their removal efficiency decreased. The uncertified mask filter showed the largest decrease in removal efficiency (26%). When the mask was soaked in alcohol, the removal efficiency decreased to a greater degree than when soaked in water. The nanofiber mask filter showed the strongest resistance to alcohol among the tested mask filters. During evaluation of mask reusability, the removal efficiency of certified mask filters decreased by 4% over 5 consecutive days (2 hours per day), and that for the uncertified mask filter decreased significantly, by 30% after 5 days.

Construction of the micro-electrolysis system by Fe0 and clay-carbon derived from oil refining for the removal of ozone disinfection by-products

In this work, the construction of iron-cetyltrimethylammonium chloride modified spent bleaching earth carbon (Fe/CTAC-SBE@C) micro-electrolysis system was first proposed for bromate removal in water. The effects of system parameters including Fe to CTAC-SBE@C mass ratio, CTAC concentration, total dosage, temperature, initial pH and reaction atmosphere were studied. Bromate removal efficiency increased with the decrease of Fe/SBE@C mass ratio from 4/1–3/1, and the further decrease of the mass ratio (from 3/1–1/4) led to the decrease of bromate removal efficiency. CTAC modification could provide the active electron transport paths (SBE@C-CTAC+-BrO3-) theoretically for bromate improved removal, and the optimal CTAC concentration was 25 mmol/L. It was found that pH was a key factor of micro-electrolysis reaction, and bromate removal decreased with the increase of pH, while the removal under neutral (pH=7) and basic (pH=9) conditions still could reach more than 75%. Surprisingly, the coexisting of Cl-, SO42- and NO3- as the electrolytes could penetrate the passivated films on the surface of iron and promote bromate removal; air atmosphere was more favorable to bromate removal than nitrogen atmosphere. In addition, based on product determination and characterization data, the removal mechanism of bromate mainly included CTAC-SBE@C adsorption and electrochemical reduction.

Impact of prefilter dilution on IgG removal in membrane-based therapeutic plasma exchange.

Previous studies have demonstrated that a "one plasma volume exchange" would result in an estimated 63% decline in pretreatment IgG levels. We evaluated the use of prefilter dilution with normal saline as a method to prevent filter failure without decreasing the efficiency of IgG removal. Twenty-one treatment sessions were analyzed and all received prefilter dilution with normal saline. Primary outcome was to determine whether prefilter dilution resulted in decreased treatment efficiency in removing the targeted IgG. Secondary outcome was filter failure in conjunction with the combined use of prefilter heparin and saline infusions. All 21 treatments (100%) received prefilter dilution with saline solution and 19/21 (90.47%) also received prefilter heparin (bolus and/or hourly infusion). We demonstrated a 60%-70% decline in pretreatment IgG levels. Prefilter dilution during membrane-based therapeutic plasma exchange based treatment did not result in a demonstrable decrease in efficiency of IgG removal while maintaining filter patency.

Monitoring of the Operating Membrane Condition Using PZT Based EMI of External Steel Pipe

Membrane systems are increasingly being used for treating water, wastewater, and reused water. However, membrane damage can decrease removal efficiency and hinder downstream applicability. Thus, the operating conditions of the membrane should be monitored. This study monitored the operating conditions of the membrane using lead zirconate titanate (PZT)-based electro-mechanical impedance (EMI) measurements in an external air pipe. Pilot-scale tests were performed to verify the performance of the proposed method. A pressure decay test (PDT) was performed using a PZT-attached air pipe, in which the pressure was measured using PZT, and a pressure gauge was employed to measure the reference pressure. The EMI signals changed according to the variations in the pressure inside the steel air pipe. To index the signal variation, the amplitude of the major peak was extracted and compared with the reference pressure. The amplitude of the major peak was inversely proportional to the pressure change. The pressure estimation equation was derived using a linear regression between the amplitudes of the major peak and the reference pressures. According to the results, the proposed monitoring system that utilizes the EMI of an external steel pipe is a potential solution to improve the sensitivity and speed of the PDT.