Good Removal Effect Research Articles

Effect of pH on caffeine removal from aqueous media by graphene/graphene oxide adsorption

Developing and continuously optimizing measures to minimize and eliminate caffeine in the water environment is significant because of its wide distribution, persistence, and possible toxicity. Graphene oxide (GO) and graphene (GN) are two attractive carbon materials with excellent adsorption performance, and pH value plays an important role in these adsorption processes. In this work, a timely theoretical insight into the adsorption and removal of caffeine (an important pharmaceutical and personal care product) on GN/GO surface at different pHs was studied by molecular dynamics simulation. In the simulation process, it is found that GN has a good removal effect on caffeine, and pH has little effect on the GN_caffeine system due to the less changed adsorption types and interaction energy between GN surface and caffeine. For GO_caffeine systems, although all the added caffeine molecules are adsorbed at low pH, the interaction energy between GO and caffeine is reduced, the hydration around caffeine molecules is reduced, and the aggregation adsorption at high pH (especially pH>7) shows fragile aggregation structures. The adsorption stability of caffeine on the surface of GO decreases, and desorption easily occurs at alkaline conditions. This characteristic may be helpful to realize the in-situ regeneration of caffeine-saturated GO.

Aeration Biofilter Filler Screening and Experimental Research on Nitrogen and Phosphorus Purification in Rural Black Water

In rural toilets, black water still remains polluted by nitrogen and phosphorus after being pre-treated by septic tanks. This study uses aerated biofilters to purify black water, screen the biofilter filler, and determine its effect on nitrogen and phosphorus purification in rural black water. This study introduced the concept of the “shape factor” into the Langmuir and Freundlich equations and optimized the isotherm adsorption model to better fit the actual dynamics of nitrogen and purification in black water. Combined with the first-order kinetic equation, the double constant equation, and the Elovich equation, the adsorption performance of seven kinds of biofilter fillers (i.e., zeolite, volcanic rock, sepiolite, ceramsite, anthracite, vermiculite, and peat) was studied. Then, the biofilter was constructed using a combination of fillers with better adsorption properties, and its ability to purify rural black water was studied. Results showed that vermiculite and zeolite had little effect on nitrogen and a high saturated adsorption of 654.50 and 300.89 mg·kg−1, respectively; peat and ceramsite had little effect on phosphorus and a high saturated adsorption of 282.41 mg·kg−1 and 233.89 mg·kg−1, respectively. The adsorption rate of nitrogen from fast to slow was vermiculite > peat > zeolite > volcanic rock > sepiolite > ceramsite > anthracite. The adsorption rate of phosphorus from fast to slow was peat > ceramsite > zeolite > sepiolite > vermiculite > volcanic rock > anthracite. Four combined biological filter fillers aided the removal of nitrogen and phosphorus from rural high-concentration black water. The combination of zeolite and ceramsite filler had a good nitrogen and phosphorus removal effect in high-concentration black water. After the system was stable, the nitrogen removal rate attained 71–73%, and the phosphorus removal rate attained 73–76% under the influent condition of total nitrogen and phosphorus concentrations of 150–162 and 10–14 mg·L−1, respectively. This study provides technical support and reference for the purification and treatment of rural black water.

Marine SINS Self-Alignment Method in Complex Interference Environment Based on MEEMD Algorithm

It is difficult to rapidly and accurately achieve alignment under complicated interferential environmental conditions with a marine strapdown inertial navigation system (SINS) subject to angular swaying interference and linear motion interference. To solve this problem, an SINS self-alignment algorithm in a complex interference environment is presented in this article. For the angular motion disturbance problem, we used the attitude-updating algorithm in the coagulation inertial coordinate system to reflect the carrier’s attitude change in real time under the swaying interference so as to eliminate the influence of angular motion disturbance. To solve the problem of linear motion interference, we first use Fourier transform analysis (FFT) to analyze the frequency characteristics of linear motion interference signals. We then adaptively decompose the original signal into a series of signal components with different time scales and local characteristics according to the amplitude and frequency using the modified ensemble empirical mode decomposition (MEEMD) algorithm. Finally, we remove and reconstruct the disturbing signal components according to the frequency characteristics of the disturbing signal to filter the line motion disturbing signal. We use the MEEMD algorithm to conduct a ship alignment test. After pre-filtering by MEEMD, high accuracy can be achieved after 100 s of alignment, and the mean square error of the heading angle is 2.85′. The test results show that the MEEMD method has a good noise removal effect. The anti-jamming initial alignment algorithm based on the MEEMD algorithm has the ability to suppress the interference of angular motion and linear motion and achieve high-precision anti-jamming initial alignment under the complicated interferential environmental conditions with angular swaying interference and linear motion interference.

A Novel Coordination Polymer as Adsorbent Used to Remove Hg(II) and Pb(II) from Water with Different Adsorption Mechanisms.

Under the hydrothermal condition, a new type of two-dimensional coordination polymer ([Cd(D-Cam)(3-bpdb)]n, Cd-CP) has been constructed. It is composed of D-(+)-Camphoric-Cd(II) (D-cam-Cd(II)) one-dimensional chain and bridging 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene (3-bpdb) ligands. Cd-CP has a good removal effect for Hg(II) and Pb(II), and the maximum adsorption capacity is 545 and 450 mg/g, respectively. Interestingly, thermodynamic studies have shown that the adsorption processes of Hg(II) and Pb(II) on Cd-CP use completely different thermodynamic mechanisms, in which the adsorption of Hg(II) is due to a strong electrostatic interaction with Cd-CP, while that of Pb(II) is through a weak coordination with Cd-CP. Moreover, Cd-CP has a higher affinity for Hg(II), and when Hg(II) and Pb(II) coexist, Cd-CP preferentially adsorbs Hg(II).

Biochar-loaded nZVI/Ni bimetallic particles for hexavalent chromium removal from aqueous solution

The biochar-loaded nZVI/Ni bimetallic nanoparticles (BC@nZVI/Ni) was synthesized by liquid phase co-reduction method and evaluated for its potential Cr(VI) removal capacity. BC@nZVI/Ni had a good removal effect in a wide pH range (2.1-9.2). The removal efficiency reached 100% for 20 mg L−1 Cr(VI) at pH ≤ 3.1. The maximum adsorption capacity of 55.52 mg g−1 was obtained at 298 K. Its excellent removal performance was mainly attributed to the abundant surface functional groups of BC and its prevention effect on nZVI agglomeration, and the reduction effect of Ni(0) on Fe(II). The main mechanism of BC@nZVI/Ni for Cr(VI) removal was electrostatic attraction, ligand exchange, surface complexation, reduction and co-precipitation. The adsorption process fitted well with Freundlich and pseudo-second-order models. It was a spontaneous and endothermic process.

Efficient degradation of anthracene in soil by carbon-coated nZVI activated persulfate

The easy passivation defect of nano zero-valent iron (nZVI) greatly limits its application in site pollution remediation. Carbon coating can effectively inhibit the passivation of nZVI, but its effectiveness in the soil is still unknown. This study investigated the feasibility of carbon-coated nZVI (Fe0@C) as a persulfate (PS) activator to degrade anthracene (ANT) in soil. The results show that the Fe0@C/PS system can remove 51.6% of ANT in the soil after 0.5 h of reaction, and reach 76.4% after 12 h of reaction. Not only that, the Fe0@C/PS system shows a good removal effect on ANT within the initial pH range of 3–9. Free radical scavenging experiments show that superoxide radicals (O2•−) and singlet oxygen (1O2) are mainly responsible for the removal of ANT, while O2•− may be mainly used as a precursor for the generation of 1O2. The activation of PS by Fe0@C can generate a large number of free radicals, and soil components (such as β-MnO2) can promote the conversion of O2•− to 1O2. Furthermore, the possible degradation pathway of ANT was also proposed. The findings are of great significance to fill up the knowledge gaps in the application of nZVI in soil remediation.

Application of progressive freeze concentration in the removal of Ca2+ from wastewater

Progressive freeze concentration (PFC) is a kind of purification technology with low energy consumption and high removal efficiency, which is widely used in water treatment. However, the effect and mechanism of PFC on high calcium wastewater are rarely studied. In order to investigate the effect of PFC on the treatment of wastewater containing high concentration of Ca2+, a progressive freezing experiment was carried out to investigate the effects of ice thickness, initial concentration, freezing temperature and initial pH on the removal rate of Ca2+, and the mechanism of PFC were analyzed. The results showed that (1) PFC had good removal effect on Ca2+ containing wastewater. Under the experimental conditions, the removal rate could reach more than 90%. By controlling a single variable, the removal effect was the best when the freezing temperature was −5 °C, and the removal rate could reach 98.18%. (2) The removal rate was positively correlated with ice thickness, freezing temperature and initial pH, positively correlated with initial concentration below 500 mg/L, and negatively correlated with initial concentration above 500 mg/L. (3) Through redundancy analysis, it was found that the experimental conditions could explain 90.7% of the characteristic parameters of Ca2+ removal. (4) The removal ability of Ca2+ was related to hydrogen bonding. The above results can be used to explain the mechanism of Ca2+ removal at the molecular level through the First-principles, which can provide a reference for the further study of the progressive freezing process for the treatment of high calcium wastewater.

Alleviation of Ultrafiltration Membrane Fouling by ClO2 Pre-Oxidation: Fouling Mechanism and Interface Characteristics.

In order to alleviate membrane fouling and improve removal efficiency, a series of pretreatment technologies were applied to the ultrafiltration process. In this study, ClO2 was used as a pre-oxidation strategy for the ultrafiltration (UF) process. Humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA) were used as three typical organic model foulants, and the mixture of the three substances was used as a representation of simulated natural water. The dosages of ClO2 were 0.5, 1, 2, 4, and 8 mg/L, with 90 min pre-oxidation. The results showed that ClO2 pre-oxidation at low doses (1–2 mg/L) could alleviate the membrane flux decline caused by humus, polysaccharides, and simulated natural water, but had a limited alleviating effect on the irreversible resistance of the membrane. The interfacial free energy analysis showed that the interaction force between the membrane and the simulated natural water was also repulsive after the pre-oxidation, indicating that ClO2 pre-oxidation was an effective way to alleviate cake layer fouling by reducing the interaction between the foulant and the membrane. In addition, ClO2 oxidation activated the hidden functional groups in the raw water, resulting in an increase in the fluorescence value of humic analogs, but had a good removal effect on the fluorescence intensity of BSA. Furthermore, the membrane fouling fitting model showed that ClO2, at a low dose (1 mg/L), could change the mechanism of membrane fouling induced by simulated natural water from standard blocking and cake layer blocking to critical blocking. Overall, ClO2 pre-oxidation was an efficient pretreatment strategy for UF membrane fouling alleviation, especially for the fouling control of HA and SA at low dosages.

Simultaneous enhancement of the H2 yield and HCl removal efficiency from pyrolysis of infusion tube under novel mayenite-based mesoporous catalytic sorbents

The promising pathway of turning energy-containing waste into renewable and sustainable energy has effectively alleviated the excessive dependence on traditional fossil energy. In this study, two different mesoporous catalytic sorbents i.e. Ca12Al14O33@mCaO and Ca12Al14O33@mCu/CaO were synthesized by sol-gel method and their promotion effect on H2 yield and simultaneous removal of harmful HCl gas during the pyrolysis of infusion tube (IT) was explored. Results indicated that the abundant internal mesoporous structure of Ca12Al14O33@mCaO made the specific surface area and pore volume of 10.26 m2/g and 0.0541 cm3/g, respectively, which provided a larger contact area for the catalytic reaction. Maximum H2 yield of 59.01 μmol g−1·min−1 was obtained under the optimal conditions while maximum HCl removal efficiency was as high as 93.36%. Compared to that of the Ca12Al14O33@mCaO, higher H2 yield (73.23 μmol g−1·min−1) recovered over Ca12Al14O33@mCu/CaO and the HCl removal efficiency also remained stable at about 90%. Both synthesized mesoporous catalytic sorbents showed an increase in H2 yield and a good removal effect on HCl during the pyrolysis process of IT.

Rational synthesis of isomorphic rare earth metal–organic framework materials for simultaneous adsorption and photocatalytic degradation of organic dyes in water

Two isomorphic rare earth metal–organic frameworks (MOFs) were synthesized by a solvothermal method. These MOFs have good removal effects on cationic and neutral dyes through simultaneous adsorption and photocatalysis.

Pilot-scale and mechanistic study of the degradation of typical odors and organic compounds in drinking water by a combined UV/H2O2-BAC process

Odor problems are challenging issues in water treatment. Advanced oxidation has a significant degradation effect on these odors; however, some issues, such as oxidant residues and disinfection byproducts, exist in the use of advanced oxidation in actual water treatment. Because of the above issues, a combined advanced oxidation process has emerged—the UV/H2O2 -biological activated carbon (BAC) process can play a strong oxidizing role in advanced oxidation and uses the physical adsorption and biological effects of activated carbon. However, there have been few studies on the odor degradation mechanism and characteristics of activated carbon biofilms in actual water treatment. This paper systematically studied the organic and odor substances removal effects and mechanism of a pilot combined UV/H2O2-BAC process. The results showed that UV/H2O2-BAC technology had a good removal effect on odor substances under long-term stable operation. The concentrations of geosmin (GSM) and 2-methylisoborneol (2-MIB) after systemic treatment were below 5 ng/L. The removal rates of DOC, UV254 and H2O2 by the combined process were 53.60%, 73.08% and 60.20%, respectively. The results of full-scan determination of GSM and 2-MIB degradation by gas chromatography–mass spectrometry (GC–MS) were consistent with those of front-track analysis. The diversity, richness and evenness of microorganisms in the lower activated carbon layer were higher than those in the middle and upper activated carbon layers. The greater the difference in the carbon layer height was, the greater the difference in the biological community structure.

Study on the Scavenging Effect of Steady-state Displacement Air Purification System on Indoor Bioaerosol

Many kinds of microorganisms, including the new coronavirus, can spread through aerosols. There are abundant bio-aerosols in indoor medical environment, and these aerosols are likely to cause infections among medical staff and patients in hospitals. Especially in the current severe situation of the new coronavirus, the use of a steady-state displacement air purification system may have a certain effect on reducing the spread of the new coronavirus or other microorganisms. To analyze the purification effect of the steady-state displacement air purification system on the bio-aerosols in the bronchoscope room of the hospital. In this study, the bio-aerosol in the outpatient department of the Respiratory Medicine Department of the bronchoscope room were collected during different time periods from 2021.04 to 2021.05. Among them, the microorganisms contained in the bio-aerosol are identified by NGS and microorganism culture and strain identification. During the experiment, the researcher took 5 sampling points to collect aerosols, performing NGS and microbial culture counting and identification to detect microorganisms. The total purification efficiency are 88.0% (NGS) and 87.5% (microbial culture count and identification results). The results above was statistically significant. In an occupant environment in the bronchoscope room, the steady-state displacement air purification system has a good removal effect on bio-aerosols. Such purification efficiency may have a positive effect on the control of the new coronavirus epidemic and various infectious diseases.

Heterotopic reaction strategy for enhancing selective reduction and synergistic oxidation ability through trapping Cr (VI) into specific reaction site: A stable and self-cleaning ion imprinted CdS/HTNW photocatalytic membrane

Ion imprinted CdS/HTNW photocatalytic membrane (IM-Cd/HT membrane) was prepared by assembling the oxidation type H2TinO2n+1·xH2O nanowires (HTNW) and the reduction type ion imprinted CdS (IM-CdS) for the removal of Cr6+ and tetracycline. Due to the imprinted cavities, Cr6+ was preferentially adsorbed and trapped at specific reaction sites for reduction reactions under the interference of other ions, and the selective reduction coefficients reached 80.01-fold and 91.92-fold. More intriguingly, Cr6+ and tetracycline reacted on the IM-Cd/HT membrane in a heterotopic manner, Cr6+ migrated to IM-CdS for selective reduction, while tetracycline migrated to HTNW for synergistic oxidation, and there was no interference between the two reactions, thereby IM-Cd/HT membrane exhibited a good synergistic balanced removal effect for Cr6+ and tetracycline. Besides, the Cr6+ flux of IM-Cd/HT membrane reached about 2952 L m−2 h−1 bar−1, and the rejection rate of Cr6+ was 62.02%. This study provides a reference for the design of functional self-cleaning membrane with good synergistic photocatalytic ability.

From wastes to functions: preparation of layered double hydroxides from industrial waste and its removal performance towards phosphates.

To control eutrophication and recover phosphate from wastewater, a calcium carbide slag and red mud composite material (CR-LDH) was prepared using industrial waste as raw material for phosphorus adsorption. The morphology and structure of synthesized CR-LDH were characterized by FT-IR, SEM, EDS, and XRD measurements. Bath adsorption test results showed that the optimal dosages of adsorbent and pH for phosphate were 5 g·L-1 and pH of 7, respectively. The experimental data could be well described by pseudo-second-order kinetic and Langmuir isotherm models, suggesting that the adsorption process of CR-LDH with respect to phosphate was a chemical and monolayer process. The theoretical maximum adsorption capacity obtained by Langmuir isotherm model was 16.06 mg·g-1 at 25 °C. The intra-particle diffusion model fitting results indicated that the adsorption of phosphate by CR-LDH was controlled by both liquid membrane diffusion and intra-particle diffusion. Phosphate was bound to CR-LDH via synergistic effect of physical adsorption, ion exchange, anion intercalation, and chemical precipitation as evidenced from a combination of microscopic analysis and adsorption mechanism study. The actual phosphate-containing wastewater investigation showed that CR-LDH not only exhibited good removal effect on phosphate, but also could greatly reduce turbidity, COD, and ammonia nitrogen, which was suitable for disposal of practical wastewater. The COD, turbidity, and NH4+-N could be reduced by 42.39%, 77.20%, and 20.71%, respectively. These results indicate that CR-LDH can be considered as potential adsorbent for the treatment of phosphate-containing wastewater, which will be helpful to achieve the goal of "treating waste with waste and turning waste into treasure".

Study on Adding Ammonium Hydrogen Fluoride to Improve Manganese Leaching Efficiency of Ammonia Leaching Low-Grade Rhodochrosite

The ammonia leaching method for treating low-grade rhodochrosite has the advantages of a good impurity removal effect and low environmental pollution. In this paper, aiming at the low leaching efficiency of low-grade rhodochrosite treated by the ammonia leaching method, studies on enhancing the leaching efficiency of manganese by using ammonium hydrogen fluoride as an additive are carried out. The effects of different ammonia concentrations, leaching temperatures, leaching times, liquid-solid ratios, stirring rates, and the addition of ammonium hydrogen fluoride on the leaching efficiency of manganese with and without ammonium hydrogen fluoride as an additive were comparatively studied, and the parameters of ammonia concentration, ammonia leaching temperature, and ammonium hydrogen fluoride dosage were optimized in the experimental study. The results indicated that ammonium hydrogen fluoride as an additive in the treatment of low-grade rhodochrosite by the ammonia leaching method could effectively increase the leaching efficiency of manganese, and the optimal process parameters were obtained. Meanwhile, the addition of ammonium hydrogen fluoride didn’t affect the quality of the steamed ammonia product.

Resource utilization of agricultural residues: one-step preparation of biochar derived from Pennisetum giganteum for efficiently removing chromium from water in a wide pH range.

Biochars derived from agricultural residues, Pennisetum giganteum, were prepared by a one-step activation method after impregnated with H3PO4. The effects of activation temperature and the H3PO4 impregnation method on the structure and performance of biochar were investigated. The characterization results of XPS, FTIR, and N2 adsorption-desorption showed that the P-containing biochar prepared by the one-step method had a large specific surface area, large pores, and abundant surface functional groups. And, the groups including C-P, O-P, and C-O participated in the adsorption of Cr(VI). Moreover, the target adsorbent has a good removal effect on Cr (VI) in a wide range of pH. The Cr(VI) removal efficiency was more than 55.92% at pH≤9. Interestingly, the adsorption results also showed that the adsorbent could offer acid groups for regulating the pH of the bulk solution and thus keep the adsorption surroundings in a narrow pH range. In addition, the target adsorbent has been proved to have good selective removal of Cr(VI). Even after repeated use for 5 times, the removal capacity of Cr(VI) is still 77.4%. This work provides a simple scheme for the high-value utilization of Pennisetum agricultural solid waste, and also confirms that the biochar activated by phosphoric acid can effectively remove Cr(VI) in the solution with wide pH range.

Modification of polyurethane sponge filler using medical stones and application in a moving bed biofilm reactor for ex situ remediation of polluted rivers

The application of moving bed biofilm reactors is a prospective water remediation technology, but its treatment efficiency needs to be further improved. In this study, moving bed biofilm reactors were applied for ex situ remediation of polluted rivers, and medical stones were newly used for modification of polyurethane sponge filler. The porosity, water-holding capacity and apparent density of the modified filler were 8.24%, 32.74% and 5.2 times higher than non-modified filler, respectively, which is more favourable to microbial attachment and growth. The developed moving bed biofilm reactors had a good removal effect on the chemical oxygen demand, ammonia, and total nitrogen of polluted urban-river water with hydraulic retention times of 12 h, 6 h, and even 3 h. The chemical oxygen demand, ammonia, and total nitrogen removal rates of moving bed biofilm reactors containing modified filler were 88.06%, 93.67% and 67.10%, respectively, which are 4.86%, 8.89% and 9.01% higher than moving bed biofilm reactors with non-modified filler, respectively, at the shortest hydraulic retention time, 3 h. In summary, this study provides a new kind of filler for moving bed biofilm reactors in ex situ remediation of polluted urban rivers, targeting rapid removal of chemical oxygen demand, ammonia, and total nitrogen.

Enhanced in-situ electro-generation of H2O2 using PTFE and NH4HCO3 modified C/PTFE electrode for treatment of landfill leachate

In this study, the carbon black/polytetrafluoroethylene (C/PTFE) electrode was prepared under the best conditions, and then it was modified by PTFE and NH4HCO3 to make a PTFE-C/PTFE electrode. PTFE-C/PTFE electrode was used to enhance H2O2 in-situ electro-generation and the electro-peroxone process (EPP) treatment of leachate. Various analytical methods results were applied to prove that the PTFE-C/PTFE electrode greatly improved the performance of H2O2 generation and electrode stability. The effects of initial pH, current intensity, ozone flow and Cl− concentration on the removal of NH4+ and chemical oxygen demand (COD) from landfill leachate were studied in the EPP with PTFE-C/PTFE as cathode (MEPP) by one factor at a time (OFAT) method. The initial pH value 7.5, current intensity 300 mA, ozone flow 875 mg/h and Cl− concentration value 4198 mg/L were selected as the best operating parameters. A response surface methodology based on box-behnken design (BBD) was employed to optimize running conditions of the MEPP of leachate. After optimization, Mineralization efficiency of the NH4+ and COD was obtained to be 79.83% and 52.14%, and biochemical oxygen demand (BOD5)/COD ratio increased to 0.38 after 4 h. The removal curves of NH4+ and COD in the MEPP conforms to the zero-order and first-order reaction kinetics, respectively. Three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) analysis shows that MEPP has a good removal effect on organics in leachate. Energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis were carried out for the cathode sediment, which was mainly magnesium ion silicate precipitation and NaCl.

Oxygen-doped porous graphitic carbon nitride in photocatalytic peroxymonosulfate activation for enhanced carbamazepine removal: Performance, influence factors and mechanisms

Due to the effective removal of refractory organic pollutants, advanced oxidation technology based on sulfate radicals (SO4·-) has attracted widespread attention. However, it is still a challenge to design an eco-friendly catalyst that efficiently activates persulfate. In this paper, oxygen-doped porous graphitic carbon nitride (OCN) was prepared by a simple thermal polymerization method to activate persulfate for removing the stubborn drug carbamazepine and showed a good removal effect. Compared with the pristine g-C3N4, the catalytic performance of OCN increased by 5.6 times under dark conditions and 4.1 time under visible light irradiation conditions, respectively. Under dark conditions, oxygen doping mainly modulated the electronic structure of the catalyst to provide more active sites to enhance persulfate activation. Under visible light conditions, oxygen doping reduced the band gap and introduced impurity defect energy level, so that the light absorption capacity was improved and photo-generated carriers were effectively separated. The results of electron paramagnetic resonance and active species trapping experiments showed that the combined action of free radicals and non-radical oxidation pathways was the main mechanism of carbamazepine degradation. Therein, singlet oxygen (1O2) was the main active species, followed by O2·- and SO4·−. In addition, environmental factor experiments showed that chloride ions, bicarbonate ions and humic acid all had significant promoting effects, and there were other interactions between humic acid and carbamazepine besides adsorption to promote the degradation reaction. Finally, high-resolution mass spectrometry identified that ring condensation, hydroxylation and carboxylation were the primary degradation pathways of carbamazepine. This work provides a feasible way for designing high-efficiency and pollution-free persulfate activators to remove refractory pollutants.

Preparation of cellulose nanofiltration membranes and their removal of typical pollutants from drinking water

Abstract Cellulose membranes have the advantages of good hydrophilicity, excellent mechanical properties, and biodegradability. Therefore, they are the first choice to replace petroleum polymer membranes. In this study, cellulose (BC) and chitosan (CS) were used as raw materials, and N-methylmorpholine-N-oxide (NMMO) was used as solvent. A new kind of cellulose nanofiltration membrane (BC-NFM), cellulose/chitosan nanofiltration membrane (BC/CS-NFM), and interfacial polymerized cellulose/chitosan composite nanofiltration membrane (IP-BC/CS-NFM) were successfully prepared by NaOH hydrolysis and chloroacetic acid carboxymethylation modification, piperazine (PIP), and 1,3,5-trimellitic chloride (TMC) interfacial polymerization, respectively. These two methods were used for the preparation of cellulose nanofiltration membranes for the first time.We also studied their structure, separation performance and their capacity to remove typical pollutants. The results showed that obvious holes appeared on the surface of the nanofiltration membrane obtained by alkali hydrolysis and chloroacetic acid carboxymethylation modification, and the cross-section showed a spongelike structure. The surface of the nanofiltration membrane obtained by interfacial polymerization formed a rough and dense separation layer. The rejection rates of the three kinds of nanofiltration membranes were all over 30% for monovalent salt ions, over 60% for divalent salt ions, over 92% for methyl orange, and over 98% for methyl blue. They had good removal effects for typical pollutants in drinking water.