Removal Of Methylparaben Research Articles

Removal of methylparaben from aqueous effluents using biobased carbon material. Experimental and DFT calculations

The emerging contaminant methylparaben was successfully removed from aqueous effluents using three carbon-based materials (BoCM-1, BoCM-2, and BoCM-3). These materials were prepared from the agro-waste Butia odorata (Bo), using the proportion of Bo: ZnCl2 of 1:1 (BoCM-1), 1:2 (BoCM-2), and 1:3 (BoCM-3). Surface area, pore size distribution, total pore volume, FTIR, Boehm titration, CHN elemental analysis, TGA, HI, and pHpzc characterized these carbon-based materials. The kinetic data were best fitted using the fractal-like pseudo-first-order (FPFO) model to explore the adsorption of methylparaben on the three adsorbent materials. The kinetic studies also show that 95 % of the adsorbent saturation (t0.95) adsorbent occurs < 8 min. The isotherm studies showed that the Liu isotherm model was the best to explore the adsorption results. The maximum values of Qmax at 45 °C (Liu) were 637.7 (BoCM-1), 869.9 (BoCM-2), and 398.7 mg g−1 (BoCM-3). Using the nonlinear van't Hoff equation, the values of ΔH° values range from –22.82 to –33.27 kJ mol−1, suggesting the adsorption process is physical. Simulated industrial wastewater was tested to check the performance of the carbon materials for potential use for actual wastewater treatment, attaining a maximum removal of 98.38 % using BoCM-2 material. DFT calculations provide a molecular picture of the physisorption of methylparaben on carbon-based materials.

Double ionic liquid reinforced g-CN nanocomposite for an enhanced adsorption of methylparaben: Mechanism, modeling, and optimization

The efficient removal of organic pollutants, especially pharmaceuticals, from aquatic environments has attracted great attentions. Application of green, multipurpose, and inexpensive compounds is being extensively favorite as adsorbent instead of the traditional chemicals or materials. In this study, sulfonated graphitic carbon nitride was modified with two ionic liquids of polyethyleneimine and choline chloride to create a novel nanocomposite (Sg-CN@IL2 NC) and to use for removal of methylparaben (MeP) from aqueous media. After confirmation of the successful synthesized using different methods, the effective parameters for MeP removal, such as initial MeP concentration, adsorbent dose, sonication time, and temperature, as well as their interactions, were experimentally examined and modeled using response surface methodology (RSM), generalized regression neural network (GRNN), and radial basis function neural network (RBFNN). The models were then optimized using desirability function analysis (DF) and genetic algorithm (GA). The results showed that MeP adsorption: a) can be explained more accurate and reliable using GRNN (AARD% = 11.67, MAE = 15.31, RAE % = 45.42, RRSE % = 55.18, MSE = 435.86, RMSE = 20.70, and R2 = 0.995) than the others; b) reached equilibrium within 7.0 min with a maximum uptake of 267.2 mg/g at a temperature of 45 °C and a neutral pH; c) followed from Freundlich (R2 = 0.999) isotherm and PSO kinetic (R2 = 0.95) models; d) is endothermic and spontaneous; e) is mainly due to π-π stacking, electrostatic and hydrogen bonding interactions. Moreover, Sg-CN@IL2 NC showed an appropriate reusability for up to five cycles. These findings demonstrate the potential of as-prepared NC as an excellent adsorbent for removal of MeP from aqueous media.

Emerging Contaminants Removal from Wastewater Using Organo-Modified Bentonite Clay

Organo-modified bentonite clay locally sourced from Bauchi State, Nigeria was prepared and used as an adsorbent for Emerging Contaminants (EC) capture from Kaduna Polytechnic female hostel wastewater. The produced adsorbent was characterized to determine the functional groups, surface area and crystal structure. Surface area for directly modified bentonite clay produced adsorbents and oxalic acid-pretreated bentonite clay adsorbent was found to be 625 m2/g and 349.2 m2/g respectively and the morphology of the produced acid-pretreated organo-modified bentonite clay adsorbents has better pore development with a higher amorphous structure. The wastewater compositions were found to contain major ECs identified to be Diclofenac, Triclosan, Methylparaben, and Bisphenol A, which account for 76.206% of the ECs that are detrimental to human and the environment. The impact of the adsorption factors; contact time, adsorbent dosage, and temperature on uptake behavior were all examined. Effect of adsorbent dosage was established which shows that all ECs removed rise rapidly from 0.5 – 1.0 g adsorbent dosage and then slowly reach a maximum of 98.65% Triclosan, 95.83% Diclofenac, 91.49% BPA, and 62.16% Methyl-Paraben removal as adsorbent dosage increases to 2g. On the other hand, as the adsorbent dosage increases to 3g, the removal rate of all ECs was observed to drop slightly and then attain maximum removal as the dosage rises to 4g. In contrast, a rise in adsorbent dosage of 2.5g gives a sudden drop in removal of Triclosane to 92.41% and Methyl-Paraben to 53.01% as well as a sharp drop in Methyl-Paraben to 33.33% and slightly drop in the removal of all other ECs. Langmuir and Freundlich isotherms models were fitted to the adsorption data and Freundlich showed best fit indicating chemisorption. The adsorption of triclosan, diclofenac, bisphenol A, and methylparaben followed pseudo second-order kinetic model.

Nickel–iron-driven heterogenous bio-electro-fenton process for the degradation of methylparaben

Discharge of emerging contaminants such as parabens in natural water bodies is a grievous concern. Among parabens, methylparaben (MP) is most prevalent due to its extensive usage in personal care and food products and has been purported to trigger hormonal-related diseases. In this regard, the bio-electro-Fenton (BEF) process garners attention for remediating refractory compounds because of its ability to generate in situ hydroxyl radicals (•OH) utilising the energy harvested from electroactive microorganisms. In the present investigation, a Ni–Fe-driven heterogenous BEF system (BEF-MFC) was used to degrade MP from different matrices. At neutral catholyte pH, 99.54 ± 0.22% of MP was removed from an initial concentration of 10 mg/L in 240 min of retention time with an estimated treatment cost of about 1.01 $/m3. The removal rate ameliorated when the catholyte pH was dropped to 3.0 and by imposing an external voltage of 0.5 V, requiring just 120 min to achieve comparable MP removal efficiencies. However, catalyst leaching was higher at acidic pH (leaching of Fe ions = 0.44 mg/L and Ni ions = 0.06 mg/L) and applying external voltage increased the treatment cost slightly to 1.08 $/m3. Further, treatment of 10 mg/L MP-spiked real wastewater at pH of 7.0 with the BEF-MFC attained 85.70 ± 3.30% and 56.50 ± 1.70% reduction in MP and total organic carbon, respectively, in 240 min. In addition, a maximum power density of 205.90 ± 2.27 mW/cm2 was harvested in the BEF-MFC; thus, portraying the dual benefit of Ni–Fe heterogeneous catalyst. Even though, Ni–Fe performed reasonably well as Fenton-cum-cathode catalyst, future endeavours should be poised to fine-tune catalysts to accelerate H2O2 and •OH generation, which will reinforce the scalability of this system.

Efficacy of Phytoremediation for Methylparaben Removal from Contaminated Water: A study by Alternanthera spp and Associated Rhizobacteria

In the present study, the potential of Alternanthera spp and its associated rhizobacteria to uptake and biodegrade methylparaben (MP) under hydroponic conditions was assessed. The experiments were conducted in vitro using glass reactors of 500-mL volume. The results indicated that the removal rates in hydroponic reactors were significantly higher (66.6±3%) than that of control reactors (<40%). MP reduction data fitted well a first-order kinetics model (R2>0.9). The presence of plants shortened the half-life (T1/2) of MP in aqueous solutions to 3.41 days compared to 34.8 days in control reactors. Bioconcentration factors (BCFs) of MP were higher for roots (1.9-5.2 L/kg) compared to stems (0-0.5 L/kg). High-tolerant rhizobacteria for MP were isolated from the roots of Alternanthera spp and characterized. It was shown that three isolates achieved noticeable efficiencies in removing MP in a separated biodegradation assay. Of the 3 isolated rhizobacteria, results revealed that Cronobacter sakazakii, diagnosed by gyrB gene, had the highest MP removal efficiency. These findings elucidated that both Alternanthera spp and a specific associated rhizobacterial strains have promising potentials in removing MP even though the latter possesses antimicrobial properties.

Removal of parabens from wastewater by Chlorella vulgaris-bacteria co-cultures

Anthropogenic activities have increased the dispersal of emerging contaminants (ECs), particularly of parabens, causing an escalation of their presence in wastewater (WW). Current WW technologies do not present satisfactory efficiency or sustainability in removing these contaminants. However, bioremediation with microalgae-based systems is proving to be a relevant technology for WW polishing, and the use of microalgae-bacteria consortia can improve the efficiency of WW treatment. This work aimed to study dual cultures of selected bacteria (Raoultella ornithinolytica, Acidovorax facilis, Acinetobacter calcoaceticus, Leucobacter sp. or Rhodococcus fascians) and the microalga Chlorella vulgaris in microbial growth and WW bioremediation - removal of methylparaben (MetP) and nutrients. The association with the bacteria was antagonistic for C. vulgaris biomass productivity as a result of the decreased growth kinetics in comparison to the axenic microalga. The presence of MetP did not disturb the growth of C. vulgaris under axenic or co-cultured conditions, except when associated with R. fascians, where growth enhancement was observed. The removal of MetP by the microalga was modest (circa 30 %, with a removal rate of 0.0343 mg/L.d), but increased remarkably when the consortia were used (> 50 %, with an average removal rate > 0.0779 mg/L.d), through biodegradation and photodegradation. For nutrient removal, the consortia were found to be less effective than the axenic microalga, except for nitrogen (N) removal by C. vulgaris w/ R. fascians. The overall results propose that C. vulgaris co-cultivation with bacteria can increase MetP removal, while negatively affecting the microalga growth and the consequent reduction of sludge production, highlighting the potential of microalgae-bacteria consortia for the effective polishing of WW contaminated with parabens.

Synthesis of biochar-CoFe2O4 nanocomposite for adsorption of methylparaben from wastewater under full factorial experimental design.

The presence of endocrine-disrupting chemicals in municipal wastewater has emerged as a threat to human health and the environment. Therefore, this study aimed to develop biochar-cobalt ferrite (BCF) nanocomposite for the removal of methylparaben from water under the full factorial experimental design of 4 factors with 3 levels (34). The biochar-CoFe2O4 nanocomposite was developed by co-precipitation method from cobalt ferrite and biochar of Eucalyptus tree bark. Adsorbent surface morphology and functional and elemental composition were carried out by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and energy-dispersive X-ray spectroscopy (EDS) techniques which showed the presence of cracks with a rough surface, reasonable surface chemical composition, and many chemical functional groups, respectively. The experimental and predicted adsorption efficiencies ranged from 25.3 to 85.6% and 21.8 to 80.3%, respectively. The maximum adsorption performance (85.6%) reduced the methylparaben concentration from 27.5 to 4.0mg/L at the optimum condition of adsorbent dose of 55mg/100mL, pH 6, contact time 90min, and the initial methylparaben concentration of 27.5mg/L. However, the adsorbent dose was the most influential main factor whereas the least influential was the interaction between solution pH and contact time under the regression model. The model also showed that 69% methylparaben removal was described by the regression model. The experimental data best fitted with the Freundlich model indicate multilayer adsorption which is the implication of physisorption. The sorption mechanism is attributed to Vander Waals forces, H-bonding, and dipole interaction. This BCF nanocomposite adsorbent appears to be promising for the removal of methylparaben from wastewater, but a further optimization process is essential to boost the treatment performance.

Enhancement of peroxymonosulfate activation by sinapic acid accelerating Fe(III)/Fe(II) cycle

Peroxymonosulfate (PMS) is more cost-effective than peroxydisulfate (PDS) and has drawn great attention presently. Low efficiency of Fe(III)/Fe(II) cycle is a great intrinsic drawback of Fenton-like system, which extremely limits its widespread application. In this study, sinapic acid (SA) as a natural and environmental-friendly reductant, was applied to enhance Fe(III)/Fe(II) cycle in PMS/Fe(III) system. The removal efficiency of methyl paraben (MEP) was 98.3% (7.2 × 10−4 s−1) within 90 min in the modified system, and the kobs was 18 times higher than in PMS/Fe(II) system. For the active species identification, SO4−, HO and Fe(Ⅳ) were all responsible for MEP degradation, while SO4− was the dominant radical. The role of SA in SA/PMS/Fe(III) system was investigated, Fe(III) was reduced to Fe(II) and SA was oxidized to quinone species in this reaction process. The concentration of Fe(II) and the activation efficiency of PMS were all improved with SA concentration increasing from 5 to 20 μM, and the contribution of active species for MEP degradation were estimated. The effect of initial pH and common anions were also investigated. For the effect of anions, HCO3− and SO42− presented inhibition effect on MEP removal, and with the HCO3− concentration increasing 1–10 mM the inhibition decreased. Low concentration Cl− promoted MEP degradation while Cl− with higher concentration exhibited inhibition. And NO3− was almost no effect on MEP degradation.

Solar energy for liquid wastewater treatment with novel TiO2 supported catalysts

Photocatalytic oxidation is promising technology for removal of recalcitrant pollutants from water. Solar energy can be an interesting radiation source since the operating costs can be lower. However, the use of powder photocatalyst is a major drawback of the technology since suitable separation technologies are required and catalysts recovery is difficult. This work aims to test the suitability of using polymeric supports to immobilize TiO 2 in the reactor and apply it for parabens removal from water by solar photocatalytic oxidation. Polyurethanes (PU) and polydimethylsiloxane (PDMS) membranes were prepared and modified with TiO 2. While PU materials are only able to adsorb (35% in 1 h) parabens whichever the modification applied, modified PDMS was able to promote parabens photocatalytic oxidation removing 20% in 1 h under solar energy. Plasma/UV modification was able to active PDMS membranes (16% of methyl paraben (MP) removal) and further entrapment of TiO 2 in the polymeric matrix did not improve the process (18% of MP removal). Thus, only the superficial TiO 2 was active. Results show that PDMS is suitable material to support TiO 2 aiming photocatalytic wastewater treatment process using the Sun as a clean and renewable energy source.

Effects of solvent composition on the synthesis of polydopamine Schiff base Cu complex to activate peroxymonosulfate for methyl-paraben degradation

Solvent composition plays an important role in the synthesis of metal complex materials, but to date little work on this issue has been reported. Herein, a unique Schiff base Cu complex catalyst (DPDA-Cu-95EtOH) was designed based on polydopamine (PDA) and 3, 5-dibromosalicylaldehyde (DBSA), and the influence of H2O added during the synthesis process on its catalytic performance towards peroxymonosulfate (PMS) activation was comprehensively investigated. Our results demonstrated that adding a small amount (5%, v:v) of H2O to the solvent absolute ethanol (EtOH) can greatly increase the Cu loading (from 3.56 at% to 10.30 at%) on the catalyst, which significantly enhanced its catalytic ability, and promoted the removal of MeP for about 4.6 times higher than that synthesized without addition of H2O. Electron paramagnetic resonance (EPR) and quenching tests revealed that 1O2, OH and SO4- were responsible for the degradation of Methyl-paraben (MeP). Moreover, the DPDA-Cu-95EtOH/PMS system not only showed excellent stability and reusability, but also exhibited considerable removal efficiency of MeP in real wastewater. Overall, this study provides new insights into the controllable synthesis of Schiff base metal complex used for the efficient activation of PMS to remove micropollutants in wastewater.

One-step preparation of Co2V2O7: synthesis and application as a Fenton-like catalyst in a gas diffusion electrode.

Bimetallic oxides and MOFs have been used as catalysts for the ORR via two-electron and Fenton-based processes. This work reports the development of a new green one-step route for obtaining Co2V2O7. The Co2V2O7 oxide was immobilized on Printex-L6 carbon and used as a catalyst for the oxygen reduction reaction (ORR) and in heterogeneous Fenton-based processes. The PL6C/2.5% Co2V2O7 sample exhibited the best performance in the ORR via a two-electron pathway, increasing the selectivity for H2O2 generation. Electrochemical impedance spectroscopy analysis showed a decrease in charge transfer resistance in the Co2V2O7/PL6C matrix. The application of a gas diffusion electrode (GDE) modified with 2.5% Co2V2O7 resulted in a 30% increase in H2O2 production compared to the unmodified GDE. The unmodified GDE promoted methyl-paraben (MeP) removal of ∼80% after 90 min treatment, whereas the modified GDE promoted ∼90% of MeP removal in 30 min. The results obtained point to the potential of Co2V2O7 in improving the efficiency of GDE when applied for the treatment of organic pollutants.

Optimization of Acetaminophen and Methylparaben Removal within Subsurface Batch Constructed Wetland Systems

Optimization of Acetaminophen and Methylparaben Removal within Subsurface Batch Constructed Wetland Systems

Application of Fenton, photo-Fenton and electro-Fenton processes for the methylparaben degradation: A comparative study

Endocrine disruptors are often reported in the literature as recalcitrant pollutants in aquatic ecosystems. For this reason, the present study focused on advanced oxidation processes, including Fenton, photo-Fenton, electro-Fenton (EF), and electrochemical oxidation (EO) as an alternative to the degradation of Methylparaben (MeP) from aqueous media. The degradation of MeP by Fenton based processes was completed in 20 min under optimal conditions (16 mg L−1 Fe2+ and 62 mg L−1 H2O2), while for the Photo-Fenton process by a reactor with a 4 W UV lamp, 4 mg L−1 Fe2+ and 52 mg L−1 H2O2, the complete degradation was attained within 16 min. Interestingly, outstanding results were achieved in the Electro-Fenton process carried out in a reactor equipped with a Ti/Ru0,3Ti0,7O2 as a cathode and a platinum anode, which, under optimized conditions (i.e. 4 mg L−1 Fe2+, j = 25 mA cm−2 and 0.05 mol L−1 Na2SO4) only 10 min was required to completely remove the contaminant from both synthetic and tap water. The MeP removal followed pseudo-first-order reaction kinetics in the following order: Electrochemical oxidation (EO) < Fenton < photo-Fenton < electro-Fenton (EF). Finally, after a comparison with the available literature concerning the oxidation of MeP, the EF system here proposed is presented as among the best in removal rate and mineralization as compared with other AOPs, performing better even in real water matrices.

Using niobium/BDD anode-based multi-cell flow reactor for the electrochemical oxidation of methyl paraben in the presence of surfactants

This study reports the electrochemical oxidation of methyl paraben (MeP) in synthetic wastes in the presence of surfactants using boron-doped diamond (BDD) anode and the interfering effect of the surfactants in MeP removal. The selected surfactants (cationic, anionic, and neutral) were used at critical micellar concentrations (CMC) and below with measurements performed to evaluate the removal rates of MeP and total organic carbon (TOC). The effects of current density (15, 30, and 45 mA cm−2), surfactant concentration, and initial pH on the efficiency of the electrochemical oxidation process were analyzed. At low concentrations, the interfering effect of the anionic surfactant (sodium dodecyl sulfate - SDS) was greater than that of the cationic surfactant (hexadecyltrimethylammonium bromide - CTAB). The complete mineralization of MeP + SDS was achieved at 45 mA cm−2 in 2 h; this was attributed to the generation of persulfate radicals at current densities higher than 15 mA cm−2. Genapol C-100 (Genapol) exerted less interference during the mineralization of MeP + Genapol compared to the systems containing other surfactants at CMC. MeP removal was favored by the use of a basic medium. The increase in surfactant concentration decreased the efficiency of MeP and TOC removal due to the formation of micelles and the intensity of MeP-surfactant interactions, apart from the increase in organic load in the system. CTAB interacted more with the ionic form of MeP in the basic medium compared to the other surfactants. All these factors influenced the mineralization of organic compounds in the systems.

Alternanthera spp. based-phytoremediation for the removal of acetaminophen and methylparaben at mesocosm-scale constructed wetlands

Recently, the spread of pharmaceuticals and personal care products (PPCPs) in the aquatic environment has steadily increased. In this study, phytoremediation technology, using an ornamental plant (Alternanthera spp.), was investigated to improve the removal of acetaminophen (AC) and methylparaben (MP) from a synthetically prepared wastewater. Three exposure lines (AC-line, MP-line and control-line) were performed with a total of 26 subsurface-horizontal constructed wetlands (SSH-CWs) that operated in batch feeding mode. The influence of plants in addition to the initial spiking concentration (20, 60 and 100 mg/L) of AC and MP on the removal efficiency was evaluated throughout the 35-days experiments. The highest removal efficiencies for AC and MP were 88.6% and 66.4%, respectively, achieved in the planted CWs; whereas only 29.7% and 21.9% were achieved in the control CWs for AC and MP, respectively. The results confirmed the role of Alternanthera spp. for accelerating the removal of AC and MP from synthetically contaminated wastewater in CWs.

Adsorption and catalytic degradation of preservative parabens by graphene-family nanomaterials

Parabens pose increasing threats to human health due to endocrine disruption activity. Adsorption and degradation of parabens by three types of graphene-family nanomaterials (GFNs) were therefore investigated. For a given paraben, the maximum adsorption capacities (Q0) followed the order of reduced graphene oxide (RGO) > multilayered graphene (MG) > graphene oxide (GO); for a given GFN, Q0 followed the order of butylparaben (BuP) > propylparaben (PrP) > ethylparaben (EtP) > methylparaben (MeP), dominated by hydrophobic interaction. MeP removal by all the three GFNs was highly enhanced (0.55–4.37 times) with the assistance of H2O2 due to additional catalytic degradation process, and MG showed the highest removal enhancement. ∙OH was confirmed as the dominant radicals responsible for parabens degradation. For MG and RGO, the metal impurities (Fe, Cu, Mn, and Co) initiated Fenton-like reaction with H2O2 to generate ∙OH. GO contained oxygen-centered free radicals, which were responsible for ∙OH formation via transferring electron to H2O2. Four degradation byproducts of MeP were identified, including oxalic, propanedioic, fumaric, and 2,5-dihydroxybenzoic acids. Combined with density function theory calculations, the degradation sites and pathways were identified and confirmed. These findings provide useful information on mechanistic understanding towards the adsorption and degradation of parabens by GFNs.

Long-term performance evaluation of granular activated carbon fluidization and biogas sparging in anaerobic fluidized bed membrane bioreactor: Membrane fouling and micropollutant removal

In this study, fluidization of granular activated carbon (GAC) by the recirculation of a bulk suspension through an anaerobic fluidized bed membrane bioreactor (AFMBR) and biogas sparging from the bottom of an anaerobic membrane bioreactor (G-AnMBR) for treating low-strength wastewater were compared to investigate organic removal and fouling rate. The chemical oxygen demand (COD) removal efficiency obtained by both the AFMBR and G-AnMBR exceeded 90 %, and the proportion of methane in the biogas produced was 60 % at the same hydraulic retention time (HRT). In the AFMBR, the transmembrane pressure (TMP) gradually increased, but a rapid TMP jump was not observed during operational period. In the G-AnMBR, the TMP increased rapidly as the biogas flowrate was 2 and 3 L/min (LPM) at 8 h of HRT while the TMP below 0.1 bar was maintained over 90 d at 4 LPM. Our results also indicated that organic micropollutants, such as Bisphenol A (BPA), Sulfamethoxazole (SMX), and Methylparaben (MeP), were removed by AFMBR almost completely. However, the G-AnMBR showed relatively low SMX and MeP removal efficiencies of 47.6 % and 74.9 %, respectively. The estimated energy required to operate the G-AnMBR was 1.37 kW h/m3, while it was only 0.06 kW h/m3 for AFMBR.

Mn(II)-Mn(III)-Mn(IV) redox cycling inhibits the removal of methylparaben and acetaminophen mediated by horseradish peroxidase: New insights into the mechanism

Catalyzed oxidative coupling reactions mediated by enzyme have been proposed as an effective remediation strategy to remove micropollutants, however, little is known about how the Mn(II) redox cycling affects the horseradish peroxidase (HRP)-mediated reactions in wastewater treatment. Here, we explored the removal of two pharmaceuticals and personal care products (PPCPs), methylparaben (MeP) and acetaminophen (AAP), in HRP-mediated reaction system with dissolved Mn (II). It was found that the conversion rate of AAP was about 284 times higher than that of MeP, and Mn (II) significantly inhibited HRP-catalyzed MeP removal but had little influence on that of AAP. X-ray photoelectron spectroscopy (XPS) and theoretical calculations demonstrated that HRP converted Mn(II) into Mn(III), and then generated MnO2 colloid, which inhibited the removal of the substrates. Moreover, the results of theoretical calculations also showed that the binding energy between HRP and Mn was 27.68 kcal/mol, which was higher than that of MeP (25.24 kcal/mol) and lower than that of AAP (30.19 kcal/mol). Therefore, when MeP and Mn (II) coexisted in the reaction system, HRP preferentially reacted with Mn(II), which explained the different impacts of Mn (II) on the removal of MeP and AAP. Additionally, Mn (II) significantly altered the product distribution by decreasing the amount of polymerization products. Overall, our work here revealed the roles of Mn (II) in the removal of MeP and AAP mediated by HRP, having strong implications for an accurate assessment of the influence of Mn(II) redox cycling on the removal of PPCPs in wastewater treatment.

Using Pressure-Driven Membrane Processes to Remove Emerging Pollutants from Aqueous Solutions

Currently, there is great concern about global water pollution. Wastewater generally contains substances called emerging pollutants, and if the removal of these pollutants is not given sufficient attention, the pollutants can enter into the water cycle and reach the water supply for domestic use, causing adverse effects on the well-being of people. In order to avoid this menace, a multitude of techniques to reduce the high concentration levels of these substances dissolved in water are being researched and developed. One of the most-used techniques for this goal is the physical-chemical separation of contaminants in water through membrane technology. In this study, different membranes were tested with the objective of investigating the removal of three emerging pollutants: caffeine, metformin, and methyl-paraben. Initially, a nanofiltration (NF) membrane was selected, and the influence of pressure was evaluated in the rejection coefficients and permeate fluxes. Next, a screening of three new membranes to remove methyl paraben was completed. The influence of the operating variables, working pressure, and methyl paraben-feed concentration was checked. Finally, the solution-diffusion model was applied to predict the behavior of the different membranes in the removal of methyl paraben. A good correlation between experimental and calculated values of permeate flux and methyl paraben concentration was obtained.

Enhanced removal of methylparaben mediated by cobalt/carbon nanotubes (Co/CNTs) activated peroxymonosulfate in chloride-containing water: Reaction kinetics, mechanisms and pathways

Chloride ion (Cl−) widely presents in natural water and wastewater, which can significantly affect the performance of sulfate radical-based advanced oxidation processes (SR-AOPs). However, few studies are available now on the generation of chlorinated by-products in the peroxymonosulfate (PMS) based systems. Here a novel catalyst (cobalt/carbon nanotubes, Co/CNTs) was synthesized and used as a PMS activator to remove methylparaben (MeP) with and without Cl−. The morphology and chemical composition of the fresh and used Co/CNTs were characterized by TEM, SEM, XRD, BET, and XPS. Results revealed that Co/CNTs exhibited significant catalytic activity toward MeP removal, and the removal efficiency increased with the augment of reaction temperature and concentrations of Co/CNTs and PMS. In the absence of Cl−, 83.2% of 10 μM MeP was degraded within 60 min by using 2 mg/L Co/CNTs and 100 μM PMS at 25 °C with pH 7.0. However, complete removal of MeP was achieved within 20 min in the presence of 100 mM Cl−, which enhanced the apparent rate constant by a factor of 4.3. Consequently, TOC removal was enhanced from 8.1% to 19.2% within 60 min. Through the quenching experiments, both SO4− and OH were found responsible for MeP degradation without Cl−, while Cl2− was the main reactive oxygen species (ROS) with 100 mM Cl−. Based on the intermediates identified via TOF-LC-MS, four potential reaction pathways were proposed, including hydrogen abstraction coupling reaction, hydroxylation, OH attack, and Cl2− attack. The intermediates also exhibited decreased toxicity compared to the parent compound based on the ecotoxicity evaluation. In addition, Co/CNTs + PMS system achieved over 60% MeP removal from real wastewater with elevated PMS concentration, indicating the process applicability. These findings provide valuable information of SR-AOPs to facilitate organic contaminants removal in Cl−-containing water.