Bisphenol A Removal Efficiency Research Articles

Degradation of endocrine disruptor, bisphenol-A, on an mixed oxidation state manganese oxide/modified graphite oxide composite: A role of carbonaceous phase

Modified graphite oxide (ΝGO) was used as a support of a manganese oxide of hausmannite type (Mn3O4) nanocatalyst and applied for the degradation of an endocrine disruptor, bisphenol-A (BPA). The prepared nanocomposite/catalyst (NGO-Mn3O4), as well as pure modified graphite oxide and manganese oxide, were characterized by X-ray diffraction, Scanning Electron Microscopy, nitrogen adsorption, X-ray photoelectron spectroscopy, Fourier Transform Infrared Spectroscopy, and potentiometric titration. The maximum removal activity for all the materials was measured at pH = 3. The NGO-Mn3O4 nanocomposite showed the highest removal efficiency of BPA at an ambient temperature without light irradiation and/or the addition of chemicals, which can be attributed to the synergistic effect of the composite formation. The nanocomposite exhibited a high catalytic activity for the degradation/oxidation of BPA, which was dramatically higher than that of the pristine Mn3O4 phase. Modified graphite oxide showed also an enhanced capability for the BPA removal, which was linked to an increased physical adsorption component.

Enhanced bisphenol A removal from stormwater in biochar-amended biofilters: Combined with batch sorption and fixed-bed column studies

A high-efficient, low-cost, and practical biochar implementation method is desired to extend biochar's powerful adsorption performance for environmental remediation. This study presents novel results with advanced biochar application by integrating biochar with biofilter for the removal of bisphenol A (BPA) from stormwater. Biochars derived from wood dust (BC0) at different pyrolytic temperatures (300, 500, and 700 °C, referred as, BC300, BC500, and BC700, respectively) were characterized and investigated for their adsorption of BPA under different pH levels and humic acid (HA) concentrations by batch sorption and fixed-bed column experiments. Microcosm biofilters vegetated with phragmites australis and amended with different biochars were constructed and used for BPA removal under different hydraulic loading rates (HLRs). Compared with other biochars, BC700 showed a high adsorption rate and capacity due to high specific surface area and pore volume. As a consequence, fixed-bed columns amended with BC700 can remove BPA more efficiently than columns with BC0, BC300, and BC500 from synthetic stormwater, though the treatment performance was affected relatively by pH change and HA concentration. A high correlation (r2 = 0.899) between the breakthrough time and the product of adsorption rate (k2) and capacity (Qmax) was found, which suggests that batch sorption experiments could be an efficient tool for prediction of breakthrough time. The BPA removal efficiency of microcosm biofilters amended with BC0, BC300, BC500 and BC700 for real stormwater containing 200 μg/L BPA at HLR of 40 cm/h averaged 4.1, 10.8, 80.3, and 98.4%, which were about 6, 15, 115, and 141 times, respectively, compared to bilfitlers without biochar amendment. Moreover, biochar amendment not only enhanced the BPA removal but also promoted phragmites australis growth, elevated nutrients and increased the E. coli removal efficiency. Hence, biochar-amended biofilters could be a promising approach for enhancing the elimination of endocrine-disrupting chemicals such as BPA from aqueous environments.

Simultaneous adsorption and oxidative degradation of Bisphenol A by zero-valent iron/iron carbide nanoparticles encapsulated in N-doped carbon matrix

The increased release and accumulation of Bisphenol A (BPA) in contaminated wastewater has resulted in the world wide concerns because of its potential negative effects on human health and aquatic ecosystems. Starting with metal-organic frameworks, we present a simple method to synthesize magnetic porous microcubes (N-doped Fe0/Fe3C@C) with graphitized shell and highly dispersed active kernel via the pyrolysis process under N2 atmosphere. Batch adsorption experimental results showed that N-doped Fe0/Fe3C@C had high adsorption capacity for BPA (∼138 mg g−1 at pH = 7 and 298 K). Degradation of BPA adsorbed on N-doped Fe0/Fe3C@C was further investigated as a function of BPA concentration, persulfate amount, temperature and solution pH. It was found that potassium peroxodisulfate could be activated by N-doped Fe0/Fe3C@C, and a large number of free radicals were generated which was crucial for the degradation of BPA. The concentration of BPA was barely changed in the individual persulfate system. BPA (10 mg L−1) was almost completely degraded within 60 min in the presence of N-doped Fe0/Fe3C@C (∼0.2 g L−1). When the BPA content increased to 25 mg L−1, the removal efficiency of BPA achieved to 98.4% after 150 min. From the XRD, Raman, and XPS analysis, the main adsorption mechanism of BPA was π-π interactions between the π orbital on the carbon basal planes and the electronic density in the BPA aromatic rings. While the superior degradation was attributed to the radical generation and evolution in phenol oxidation. This work not only proved the potential application of N-doped Fe0/Fe3C@C in the adsorption and degradation of BPA, but also opened the new possibilities to eliminate organic pollutants using this kind of magnetic materials in organic pollutants’ cleanup.

Monitoring three typical phenol endocrine disrupting compounds in drinking water of Suzhou urban area – from raw water to tap water

ABSTRACTIn this work, three typical phenol endocrine-disrupting compounds (EDCs), namely Bisphenol A (BPA), 4-nonylphenol (4-NP) and 4-tert-octyphenol (4-t-OP), were detected in water samples from the whole drinking water supply chain of seven water plants at three hydrographic periods in Suzhou, China. Almost all of the drinking water in urban area of Suzhou city is provided by the seven water plants. Every link of drinking water supply, including raw water, finished water and tap water were monitored. The results indicated that BPA and 4-NP were detected in all samples with the concentration of 0.067–0.118 μg L−1 and 0.111–0.350 μg L−1, respectively, while 4-t-OP could be detected in only a few raw water samples with the concentration lower than its limit of quantitation (LOQ). The levels of BPA and 4-NP in raw water were significantly different among three hydrographic periods and the highest concentration can be observed in dry period. The difference in removal efficiency of BPA and 4-NP in seven water plants was also observed among three hydrographic periods, e.g. relative higher in dry period for BPA and in flow period for 4-NP. Potential risk assessment hinted that BPA and 4-NP in raw water showed a low to medium and a medium to high risk respectively to aquatic environment, while in tap water, the health risk from BPA and 4-NP could be ignored on human.

Synergistic degradation of bisphenol A by pulsed discharge plasma with granular activated carbon: Effect of operating parameters, synergistic mechanism and possible degradation pathway

A hybrid gas-liquid pulsed discharge plasma (PDP) system combined with granular activated carbon (GAC) was established to investigate the bisphenol A (BPA) degradation. The results exhibit excellent synergistic effect in PDP with GAC system (combination system) for BPA degradation. 4 g amount of GAC, 20 mg/L BPA concentration, acidic solution condition and higher gas flow rate are beneficial for BPA degradation; The highest BPA removal efficiency, mineralization and kinetics constants can reach 98.7%, 34.6% and 0.075 min−1 respectively. The decreased O3 and enhanced •OH in water after GAC addition illustrate O3 can be catalyzed by GAC and lead to the formation of •OH. The radical scavenger test illustrates the role of •OH during BPA degradation. The aviation of nature and concentration of fluorophores during BPA degradation is explored by three-dimensional excitation emission fluorescence spectra. Organic acids including formic acid, acetic acids, oxalic acid and inorganic acid including nitric acid and nitrous acid can be produced during pulsed discharge and BPA degradation. The intermediates during the BPA degradation were identified by liquid chromatograph-mass spectrometer (LC-MS). Based on the intermediates, the proposed degradation pathway is presented. The SEM technology demonstrates that GAC can be regenerated by the discharge process.

Activation of persulfate by a novel Fe(II)-immobilized chitosan/alginate composite for bisphenol A degradation

In this study, a novel Fe(II) immobilized chitosan/alginate composite (Fe-Chitoal) was prepared via a simple crosslinking reaction to activate persulfate (PS) to degrade bisphenol A (BPA). The newly synthesized Fe-Chitoal was characterized by scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, which indicated that Fe was successfully imprinted into the composite. The PS/Fe-Chitoal system demonstrated a much higher removal efficiency of BPA (99.5%) than the conventional PS/Fe(II) system (69.2%) with a negligible amount of Fe ions released into the solution. The effects of different experimental conditions, including the concentration of PS, concentration of Fe-Chitoal, and pH, on the removal of BPA were also investigated. The removal rate increased with increasing amounts of PS and Fe-Chitoal, and a high removal efficiency was maintained at a pH of 2–10. The PS/Fe-Chitoal system was rarely affected by high concentrations of anions (Cl−, SO42−, NO3−, and HCO3−), and the composite catalyst could be reused in a synthetic sewage solution. To simply separate the material, a Fe-Chitoal mesh bag was fabricated, which showed a consistent catalytic reactivity toward PS and BPA removal suggesting practical field applications.

Efficient removal of bisphenol A by superoxide radical and singlet oxygen generated from peroxymonosulfate activated with Fe0-montmorillonite

For eliminating organic pollutants from wastewater, Fe0 or Fe0-composites as catalyst for peroxymonosulfate (PMS) activation have attracted increasing attention in advanced oxidation processes. In this work, a novel Fe0-montmorillonite composites (Fe-Mt-C-H2) have been prepared by thermal reduction and used as an activator for PMS to remove bisphenol A (BPA). The removal efficiency of BPA (25 mg·L−1) and total organic carbon (TOC) were 99.3% and 70.6%, respectively, in the presence of Fe-Mt-C-H2 (0.4 g·L−1) and PMS (1 mM) at pH of 3. Electron paramagnetic resonance (EPR) spectroscopy and radical scavenger studies demonstrated that superoxide radical (O2−) and singlet oxygen (1O2) were the crucial reactive oxygen species (ROS) in the Fe-Mt-C-H2/PMS system rather than sulfate (SO4−) and hydroxyl radical (·OH). Besides, it was found that pH had a great influence on the catalytic oxidation rate of BPA and the Fe-Mt-C-H2 exhibited best catalytic performance and reusability at initial pH of 3. Furthermore, the constituents of the iron surface oxidation layer at different initial pH were investigated with X-ray photoelectron spectroscopy studies, which indicated that the major constituents were Fe3O4 in acidic solution and contained α-Fe2O3, FeO and FeSO4(s) in alkaline or neutral solution. The findings of this study provide new insights into the activation mechanism of PMS by Fe0-composites and exhibit a promising application of Fe-Mt-C-H2 in wastewater treatment.

Sandwich-like Co3O4/MXene composite with enhanced catalytic performance for Bisphenol A degradation

MXene, as an emerging group of two-dimensional layered material, attracted more and more attention due to its extraordinary physical properties. In this study, a sandwich-like Co3O4/MXene (CMs) composite was prepared via a one-step heating method and used as a novel catalyst to activate peroxymonosulfate (PMS) for Bisphenol A (BPA) degradation. The sample (CM-20%) achieved an efficient catalytic activity with 95% removal of BPA at 20 mg/L within 7 min. Meanwhile, the parameters in the degradation process were optimized. In particular, CM-20% obtained excellent BPA removal efficiency in a wide pH range (4–10). Anions like NO3− and Cl− had a slight negative effect while HCO3− had a great negative effect on catalytic activity in CM-20%/PMS system. Notably, the catalyst exhibited a good performance after 5 consecutive runs and the leached cobalt ion was negligible. Electron paramagnetic resonance (EPR) analysis and quenching tests identified SO4− and OH were the reactive species. The pathway of degradation was also detected by analyzing its intermediates using LC-MS. This work provides a new field of MXene composite material for PMS remediation of organic pollutant and widens the application of MXene in environmental remediation field.

Effect of Bisphenol A on the extremophilic microalgal strain Picocystis sp. (Chlorophyta) and its high BPA removal ability

Bisphenol A (BPA) effects and removal by an alkaliphilic chlorophyta, Picocystis, were assessed. BPA at low concentrations (0–25 mg L−1) did not inhibit the Picocystis growth and photosynthesis during 5 days of exposure. At higher BPA concentrations (50 and 75 mg L−1), the growth inhibition did not exceed 43%. The net photosynthetic activity was dramatically reduced at high BPA concentrations while, the PSII activity was less affected. The exposure to increasing BPA concentrations induced an oxidative stress in Picocystis cells, as evidenced by increased malondialdehyde content and the over-expression of antioxidant activities (ascorbate peroxydase, gluthation-S-transferase and catalase). Picocystis exhibited high BPA removal efficiency, reaching 72% and 40% at 25 and 75 mg L−1 BPA. BPA removal was ensured mainly by biodegradation/biotransformation processes. Based on these results, the extended tolerance and the high removal ability of Picocystis make her a promising specie for use in BPA bioremediation.

Dracaena sanderiana endophytic bacteria interactions: Effect of endophyte inoculation on bisphenol A removal

Bisphenol A (BPA) is one of the most abundant endocrine-disrupting compounds which is found in the aquatic environment. However, actual knowledge regarding the effect of plant-bacteria interactions on enhancing BPA removal is still lacking. In the present study, Dracaena sanderiana endophytic bacteria interactions were investigated to evaluate the effect of bacterial inoculation on BPA removal under hydroponic conditions. Two plant growth-promoting (PGP) bacterial strains, Bacillus thuringiensis and Pantoea dispersa, which have high BPA tolerance and can utilize BPA for growth, were used as plant inocula. P. dispersa-inoculated plants showed the highest BPA removal efficiency at 92.32 ± 1.23% compared to other inoculated and non-inoculated plants. This was due to a higher population of the endophytic inoculum within the plant tissues which resulted in maintained levels of indole-3-acetic acid (IAA) for the plant's physiological needs and lower levels of reactive oxygen species (ROS). In contrast, B. thuringiensis-inoculated plants had a lower BPA removal efficiency. However, individual B. thuringiensis possessed a significantly higher BPA removal efficiency compared to P. dispersa. This study provides convincing evidence that not all PGP endophytic bacteria-plant interactions could improve the BPA removal efficiency. Different inocula and inoculation times should be investigated before using plant inoculation to enhance phytoremediation.

Rapid microwave irradiation synthesis and characterization of Bi7O9I3 photocatalyst for the degradation of bisphenol A

Bi7O9I3 photocatalysts were successfully synthesized by a microwave irradiation method at different temperatures and times. The effects of synthesis conditions on the phase, optical property, surface morphology and elemental composition of as-synthesized catalysts were investigated. Results revealed the presence of Bi7O9I3 with band gap energy ranging from 2.20 eV to 2.24 eV. Moreover, photocatalytic activity of Bi7O9I3 was evaluated by the degradation efficiency of bisphenol A (BPA) under xenon lamp illumination. Among the samples, Bi7O9I3 synthesized at 160 °C for 30 min displayed the best photocatalytic performance. The removal efficiency of BPA was affected by pH value of BPA solutions and gradually enhanced with the increase of pH from 3 to 10.

Performance of a membrane bioreactor in extreme concentrations of bisphenol A.

In this study, a submerged membrane bioreactor was used to study the effect of low and high bisphenol A (BPA) concentration on the sludge biological activity. The pilot was operated over 540 days with hydraulic retention time and solid retention time of 5.5 hours and 140 days, respectively. As a hydrophobic compound, BPA was highly adsorbed by activated sludge. In lower concentrations, the biodegradation rate remained low, since the BPA concentration in the sludge was lower than 0.5 mg/g TS; yet, at an influent concentration up to 15 mg/L, the biodegradation rate was increasing, resulting in 99% BPA removal efficiency. The result for chemical oxygen demand removal showed that BPA concentration has no effect on the heterotrophic bacteria that were responsible for the organic carbon degradation. In higher concentrations, up to 16 mg of BPA was used for each gram of sludge as a source of carbon. However, the activity of autotrophic bacteria, including nitrifiers, was completely halted in the presence of 20 mg/L of BPA or more. Although nitrification was stopped after day 400, ammonia removal remained higher than 70% due to air stripping. Assimilation by bacteria was the only removal pathway for phosphorus, which resulted in an average 35% of P-PO4 removal efficiency.

Modeling and kinetics study of electrochemical peroxidation process for mineralization of bisphenol A; a new paradigm for groundwater treatment

To remove the bisphenol A (BPA) effectively from groundwater great attempts made in the current work to optimize the operating parameters of electrochemical peroxidation (ECP) process using response surface methodology (RSM) based on central composite design (CCD). The obtained data from ANOVA analysis revealed the significance of experimental variables. The obtained removal efficiency of BPA demonstrated that the predicted quadratic model is highly adequate and applicable. According to the experimental data, it found that the best removal efficiency of 100% achieved at initial concentrations BPA of 5.0 mg·L−1, hydrogen peroxide amount of 55.0 μL, pH 3.0, reaction time 12.0 min, and current density 6.0 mA·cm−2. The rate of the oxidation process of BPA reduced by increasing the amount of H2O2 and Fe2+ ions, which might be due to the reducing the amount of hydroxyl free radicals involved in the scavenging reaction. The kinetics of the process follows the pseudo first-order model with rate constants of 0.596 min−1 (R2 = 0.9908). Since, most of the reported studies are based on one factor at the time method, in the current study, RSM was used to evaluate the main effects of parameters, their simultaneous interactions and quadratic effect to achieve the optimum condition for EC process. The kinetics studies of ECP process provide valuable information on the mechanism of the degradation process that attributes to the presence of free hydroxyl radicals.

Effect and removal of bisphenol A by two extremophilic microalgal strains (Chlorophyta)

The effects and the removal efficiency of bisphenol A (BPA) on two extremophilic Chlorophyta strains, an alkaliphilic Picocystis and a thermophilic Graesiella, were assessed. BPA was shown to inhibit the growth and photosynthesis of both species, but to a greater extent for Graesiella. The growth IC50 (4 days) was 32 mg L−1 for Graesiella and higher than 75 mg L−1 for Picocystis. Oxidative stress was induced in both strains when exposed to increasing BPA concentrations, as evidenced by increased malondialdehyde content. BPA exposure also resulted in an over-expression of antioxidant activities (ascorbate peroxidase, glutathione S-transferase and catalase) in Picocystis whereas they were repressed in Graesiella. Both species exhibited high BPA removal efficiency, reaching 72% for Picocystis and 52.6% for Graesiella at 25 mg L−1. BPA removal was mostly attributed to biodegradation for both species. Overall, according to its extended tolerance and its removal capacity, Picocystis appeared to be a promising species for the BPA bioremediation even at high contamination levels.

UVA-UVB activation of hydrogen peroxide and persulfate for advanced oxidation processes: Efficiency, mechanism and effect of various water constituents

In the present work we investigate the activation efficiency of H2O2 and S2O82− using UVA and UVB radiation. Bisphenol-A (BPA) is used as model pollutants to estimate the oxidative process efficiency in simulated and real sewage treatment plant waters. Particular attention is paid to the BPA removal efficiency and to the radical mechanism involvement considering the effect of typical inorganic water constituents (carbonates and chloride ions) and organic matter. Despite a detrimental effect observed when carbonate ions are in solution using both hydrogen peroxide and persulafate, the presence of high chloride ions concentration was found to improve BPA removal using S2O82− as radical precursor. This enhancement, investigated combining chemical kinetic model approach and laser flash photolysis experiments, is attributed to the formation of hydroxyl radical and chlorine radical species from sulfate radical. Different transformation products are identified by means of GC–MS and HPLC-MS analyses. Moreover, experiments using sewage treatment plant water (STPW) spiked with BPA are performed in order to assess the efficiency of oxidative processes in a simulated treatment systems activated using UVA + UVB radiations.

Mussel-inspired co-deposition to enhance bisphenol A removal in a bifacial enzymatic membrane reactor

In this study, the biocatalytic membranes were prepared by ‘reverse filtration’ of laccase and subsequently various mussel-inspired coating strategies: single dopamine (DA) deposition, DA/polyethyleneimine (PEI) co-deposition, and DA/Cu2+ co-deposition, where nanofiltration (NF) membranes were used as the matrix to further exploit the potential of the biocatalytic membranes. Such prepared biocatalytic membranes were enzymatically active on both sides, making it possible to construct a bifacial enzymatic membrane reactor (EMR) for highly efficient micro-pollutants removal (taking bisphenol A (BPA) as an example). Compared with the single polydopamine (PDA) coated membrane, the biocatalytic membranes prepared by DA/PEI and DA/Cu2+ co-depositions exhibited much better performances in terms of enzyme loading, activity and permeability as well as the stability of immobilized enzyme. The BPA removal efficiency was highest for the EMR with the PDA/Cu2+ coated membrane attributed to copper-enhanced electron transfer, while it was lowest for the EMR with the PDA/PEI coated membrane due to the high diffusional resistance of the dense PDA/PEI layer. Meanwhile, the mechanism for performance deterioration of biocatalytic membrane during BPA treatment was revealed, and it was found that the trade-off between BPA removal efficiency and long-term stability could be broken by applying the bifacial EMR with PDA/Cu2+ coated membrane in flow-through mode, since the pressure-induced convective mass transfer improved the substrate accessibility to enzyme together with products removal.

Non-radical-dominated catalytic degradation of bisphenol A by ZIF-67 derived nitrogen-doped carbon nanotubes frameworks in the presence of peroxymonosulfate

Nitrogen-doped carbon materials have been one of the most remarkable families of materials with promising applications in many fields. In this study, a series of nitrogen-doped carbon nanotubes frameworks (NCNTFs) with distinguishable nitrogen content and graphitization degree have been successfully prepared through in situ transformation of ZIF-67 under N2/H2 atmosphere at different pyrolysis temperature. Compared with conventional nitrogen-doped carbon materials derived from metal-organic frameworks, the formation of intertwined carbon nanotubes harvests desirable mesoporous structure that is favorable for the mass transfer and diffusion of reaction substances. When they are applied for catalytic degradation of Bisphenol A (BPA) in the presence of peroxymonosulfate (PMS), NCNTFs-800 (pyrolyzed at 800 °C) promises higher BPA removal efficiency than its counterparts from other pyrolysis temperature, as well as porous carbon derived from ZIF-8. Radical-quenching tests and electron paramagnetic resonance measurements verify that non-radical process (1O2) dominates BPA degradation over NCNTFs-800, and some common radicals (such as OH, SO4− and O2−) only play auxiliary roles. It is believed that the good balance between surface graphitic nitrogen sites and graphitization degree is responsible for the enhanced catalytic performance, and facilitates electron transfer from BPA to PMS to induce the non-radical pathways. Besides, some potential influential factors, including catalyst/Oxone dosage and reaction temperature are investigated, and the effects of anions, humic acid, and actual wastewater on BPA degradation are also elucidated in detail. Finally, several intermediates are identified by GC–MS analysis and the possible degradation pathways are deduced tentatively.

Microbial composition of biofilm treating wastewater rich in bisphenol A

ABSTRACTAlthough microbial degradation plays a major role in the removal of bisphenol A (BPA) from water environments, there is little information on the effect of BPA on microorganisms in wastewater treatment systems. The aim of this study was to determine the dynamics of the microbial communities in biofilm growing on porous ceramic supports in a column up-flow reactor during exposure to BPA at increasing concentrations from 0 to 10 mg L−1. Independent of BPA load, the efficiency of BPA removal was about 90%. Groups of microorganisms that differ in their sensitivity to the presence of BPA in wastewater were identified. The core microbial genera in the biofilm were Acidovorax, Pseudoxanthomonas and Acinetobacter. Arenimonas sp., Thauera sp. and Acidobacterium sp. were the main components of the biofilm in the absence of BPA in wastewater. Increased abundances of Pseudomonas sp., Acidovorax sp. and Luteimonas sp. in BPA-exposed biofilm indicate that these genera may have played important roles in BPA biodegradation. A correlation between Pseudomonas sp. abundance and BPA removal efficiency indicates that BPA was used directly as a source of carbon and energy for growth. This study indicates that the use of the biofilm reactor enables effective BPA removal from wastewater and expands knowledge about the microbial structure of communities responsible for BPA degradation.

Synthesis and characterization of polysulfone/graphene oxide nano-composite membranes for removal of bisphenol A from water

Bisphenol A (BPA) is an emerging contaminant of water resources that disrupts endocrine function. Attempts are continuing to develop cost-effective methods to remove BPA from water environments. The aim of this study was to prepare and characterize polysulfone/graphene oxide nano-composite membranes for removal of BPA from water. Three membranes were synthetized using phase inversion method: polysulfone membrane as PSF and two polysulfone/graphene oxide nano-composite membranes with graphene oxide (GO) weight ratios of 0.4 and 1.0% as PSF/GO 0.4% and PSF/GO 1.0%, respectively. The membrane characteristics including morphology, surface roughness, pore size, zeta potential and presence of functional groups were determined using field emission scanning electron microscopy, atomic force microscopy, streaming potential, and attenuated total reflectance Fourier transform infrared spectroscopy techniques. Inclusion of GO remarkably increased permeate flux of the membranes, so that pure water flux of PSF, PSF/GO 0.4% and PSF/GO 1.0% at operating pressure of 2 bar was determined 226, 449 and 512 L/m2 h, respectively. The membrane PSF/GO 0.4% with the most negative zeta potential (−10.46 mV) and the highest BPA removal efficiency was determined as the optimal membrane. The optimum conditions of input pressure, operating time, initial concentration of BPA, and pH for BPA removal efficiency by PSF/GO 0.4% were determined using surface response methodology to be 1.02 bar, 10.6 min, 7.5 mg/L, and 5.5, respectively. By optimizing the conditions of operating parameters, experimental BPA removal efficiency by PSF/GO 0.4% reached to as high as 93%.

Persulfate enhanced photocatalytic degradation of bisphenol A by g-C3N4 nanosheets under visible light irradiation

The enhancement of g-C3N4 photocatalytic degradation of bisphenol A (BPA) via persulfate (PS) addition was investigated under visible light irradiation. The effects of various parameters on the BPA degradation were investigated, such as catalysts dosage, PS concentrations, initial pH value and BPA concentration. The results showed that g-C3N4 nanosheets exhibited superior photocatalytic activity toward BPA degradation as compared with bulk g-C3N4. The addition of PS can further improve the g-C3N4 photocatalytic performance for BPA degradation. With 5 mM PS, the degradation rate of BPA was increased from 72.5% to 100% at 90 min, and the corresponding first-order kinetic constants were increased from 0.0028 to 0.0140 min−1. The removal efficiency of BPA increased with the decrease of solution pH value. The active radicals in the reaction system were tested by electron spin resonance (ESR) and radicals quenching experiments. Instead of persulfate radicals’ oxidation, it was proposed that the main active radicals for BPA degradation were superoxide radicals and the photogenerated holes.