Removal Of P-nitrophenol Research Articles

Modification of polyacrylonitrile-based activated carbon fibers and their p-nitrophenol adsorption and degradation properties

Activated carbon fibers (ACFs) are widely used adsorbent materials for wastewater treatment. In this study, polyacrylonitrile-based ACFs (PAN–ACF) were modified with oxalic acid to promote their adsorption of p-nitrophenol (PNP) in wastewater. The obtained results revealed that the adsorption efficiency of the modified ACFs amounted to 98.05%. The photocatalytic degradation of PNP by ACFs loaded with nano-TiO2 and nano-ZnO photocatalysts was examined as well; under ultraviolet (UV) light irradiation, their PNP removal rates reached 99.85% and 98.31%, respectively. Moreover, the effects of pH, PNP concentration, and catalyst concentration on the PNP adsorption efficiency were systematically investigated. By conducting kinetic studies, it was found that the PNP adsorption on the PAN–ACF surface followed a pseudo-first-order model, while the PAN–ACF/TiO2 and PAN–ACF/ZnO obeyed a pseudo-second-order model, and all samples followed the Langmuir adsorption isotherm. Additionally, an integrated high-pressure microwave reactor was designed and fabricated, and the possibility of degrading PNP through the microwave-assisted catalytic oxidation by PAN–ACF/TiO2 was considered. The results of this work suggest that the novel modified PAN–ACF, PAN–ACF/TiO2 and PAN–ACF/ZnO adsorbents are promising materials for the removal of PNP-based pollutants from wastewater due to their facile application procedure, low fabrication costs, and good scale-up abilities.

Controllable Approach to Carbon‐Deficient and Oxygen‐Doped Graphitic Carbon Nitride: Robust Photocatalyst Against Recalcitrant Organic Pollutants and the Mechanism Insight

AbstractPolymeric g‐C3N4 is a promising visible‐light‐responsive photocatalyst; however, the fast recombination of charge carriers and moderate oxidation ability remarkably restrict its photocatalytic oxidation efficiency towards organic pollutants. To overcome these drawbacks, a self‐modification strategy of one‐step formaldehyde‐assisted thermal polycondensation of molten urea to prepare carbon‐deficient and oxygen‐doped g‐C3N4 (VC‐OCN) is developed, and the carbon vacancy concentration is well‐controlled by changing formaldehyde dosage. The VC‐OCN catalysts exhibit interesting carbon vacancy concentration‐dependent photocatalytic removal efficiency to p‐nitrophenol (PNP) and atrazine (ATN), in which VC‐OCN15 with appropriate carbon vacancy concentration displays significantly higher pollutant removal efficiency than bulk g‐C3N4. The apparent first‐order rate constant of VC‐OCN15 for PNP and ATN removal is 4.4 and 5.2 times higher than that of bulk g‐C3N4. A combination of the experimental results and theoretic calculations confirm that the synergetic effect of carbon vacancies and oxygen doping sites can not only delay the recombination of charge carriers but also facilitate adsorption of oxygen molecules on the carbon vacancies, which leads to the generation of plentiful active oxygen species including not only superoxide anion radicals but also indirectly formed hydroxyl radicals and singlet oxygen. These active oxygen species play a dominant role in the removal of target pollutants.

A novel strategy to achieve simultaneous efficient formate production and p-nitrophenol removal in a co-electrolysis system of CO2 and p-nitrophenol

A co-electrolysis system of CO2 and organic pollutants (CES) is promising for CO2 conversion and organic pollutant removal. However, it is still challenging to achieve the simultaneous efficient CO2 conversion and organic pollutant removal by tuning the electrode potential. Herein, we report a novel electrolysis mode for the CES. The anode potential was controlled by a potentiostat, while the cathode potential was controlled by changing the cathode surface area. By controlling the anode potential at 1.8 V and the cathode surface area at 0.1 cm2 (i.e., the anode/cathode surface area ratio was 10), both the anode and cathode potential values in the CES could be maintained to where CO2 reduction to formate and organic pollutant (p-nitrophenol in this study) removal were favored. The efficiencies for formate production and p-nitrophenol removal were almost the same as their optimal values in the individual electrochemical processes. Moreover, compared to the conventional electrolysis mode, our proposed electrolysis mode increased the current efficiency 1.25–1.41 times. Overall, this study clearly demonstrated that our proposed electrolysis mode is a feasible strategy to obtain simultaneous efficient formate production and organic pollutant removal in the CES, which can accelerate the use of the CES in industrial applications.

Reduction of p-nitrophenol in an airlift electrochemical reactor with iron electrodes

Kinetic experiments of removal of p-nitrophenol (p-NP) from aqueous solution were performed in an airlift electrochemical reactor at 19.3 ± 0.5 °C and 1 atm. It was demonstrated that a simple and low-cost electrochemical reacting system with iron electrodes is able to reduce efficiently p-NP to a more friendly environment product. The rate limiting step of p-NP reduction and production of p-aminophenol at apparent rate constants between 6.03 ± 0.22 × 10–5 and 9.85 ± 0.45 × 10–5 s−1 was the one-electron transfer reaction at the liquid-cathode interface. The reaction involved the substituent nitro group as electron withdrawer with p-NP adsorbed on the cathode in a quasi-equilibrium condition. The residual amount of soluble ferrous ion, the major product of electrolytic oxidation of zero valent iron at the anode, was lower than the allowable limit of 2.68 × 10–4 mol L−1. The kinetics of oxidation of Fe2+ to ferric ion and the hydrolysis of Fe3+ to iron hydroxides was properly described by a reaction rate that was proportional to the partial pressure of oxygen, first- and nth-order in Fe2+ and hydroxyl anion, respectively. The rate constant of the overall oxidation/hydrolysis reaction of Fe2+ was 6.31 ± 0.63 × 1014 L2 mol−2 atm−1 s−1 for pH from ∼5.2–6.6 (n = 2) and 3.75 ± 0.88 × 10–8 mol L−1 atm−1 s−1 for pH from ∼6.9–8.8 (n = −1).

Hydroxyl Radical-Involving p-Nitrophenol Oxidation during Its Reduction by Nanoscale Sulfidated Zerovalent Iron under Anaerobic Conditions.

Sulfidated zerovalent iron (S-ZVI) has been extensively used for reducing pollutants. In this study, the oxidation process in the reductive removal of p-nitrophenol (PNP) by S-ZVI was confirmed under anaerobic conditions. We revealed that a PNP oxidation process involving •OH resulted from the H2O2 activation by surface-bound Fe(II) in S-ZVI, in which H2O2 was generated via a surface-mediated reaction between water and FeS2. Only the PNP reduction process occurred for ZVI. Herein, efficient PNP degradation by S-ZVI resulted from two functions: reduction into p-aminophenol due to enhanced electron transfer and PNP oxidation into p-benzoquinone by •OH radicals from the interaction of surface-bound Fe(II) and in situ generated H2O2, the contributions of the oxidation and reduction processes to PNP degradation over S-ZVI were 10 and 90%, respectively. Sulfur in S-ZVI suppressed the pH increase in the reaction media and produced more surface-bound Fe(II) than ZVI for •OH generation via the heterogeneous Fenton reaction process. Since different degradation pathways could lead to different effects on the water environment, such as toxicity, our findings suggest that the oxidizing process induced by S-ZVI during groundwater decontamination should be considered.

Uptake of p-Nitrophenol (PNP) from model aqueous solutions using raw and quaternised Afromomum melegueta peels

Anthropogenic activities contribute large amounts of pollutants to the environment which threaten animal and human health. There is increased realization of the effect of these toxins on surface and ground water, consequently, their elimination is vital in rendering secure water for drinking as well as culpable release of effluents to our habitats. Phenolic compounds cause serious health effects to both humans and animals; a p-Nitrophenol concentration of 1 ppb changes the taste and odour of water as well as meat and fish quality. In humans, exposure to PNP causes eye and skin burns while its interaction with blood leads to confusion, cyanosis and unconsciousness. It is imperative therefore to find ways for removing PNP from water. Among the available techniques for removing PNP from water, adsorption is more convenient and offers more advantages because of its design, simplicity, and operating flexibility. The present study involved application of peels of raw Afromomum melegueta (RAM) and quaternised Afromomum melegueta (QAM) to remove PNP from water through adsorption. The raw adsorbents were modified with a quaternary ammonium salt to improve their uptake efficiency. The impact of experimental parameters; contact time, pH, sorbent dose, temperature and concentration were investigated. Attenuated FTIR technique was employed to characterize the adsorbent materials. It was established that the quaternary ammonium compound was anchored chemically within the cellulose structure of Afromomum melegueta peels. The behavior of adsorption of PNP was investigated using Langmuir and Freundlich isotherm models. The physical sorption load was 8.70 and 106.38 mg/g for RAM and QAM peels respectively from Langmuir adsorption equation. Uptake of PNP is high at the first 30 mins of contact and at sorbent dosage of 0.01 g and 0.03 g for RAM and QAM respectively. Quantity of PNP removed increases as the initial concentration rises however, adsorption decreases after a concentration exceeding 30 mg/L. The ideal pH and temperature for PNP removal is at pH 3 and 25 ˚C respectively. In conclusion, the findings suggest that Afromomum melegueta peels can be friendly to the environment, cheap biosorbents and efficient which can be applied for the uptake of PNP from drinking water

P-Nitrophenol degradation by activated persulfate

The degradation of p-nitrophenol (PNP), which is listed as a priority pollutant by the Environmental Protection Agency (EPA), was investigated in this work by the activated persulfate oxidation. Different forms of persulfate activation (namely thermal, by medium basification and with an iron salt catalyst) were evaluated, apart from founding the best operating conditions for maximizing process performance (assessed in terms of PNP removal and mineralization — evaluated by the overall total organic carbon (TOC) reduction). For the thermal and alkaline activation of persulfate, the temperature was varied in the range of 30 to 90 ºC and the pH between 3.0 to 9.0, respectively, being found that best performances exist for a reaction temperature of 70 ºC while pH above 7.0 is not necessary. In short reaction times (≤10 min) the oxidation of PNP, mineralization and consumption of persulfate were successfully fitted to a second-order kinetic model and the apparent activation energies determined. The effect of persulfate concentration was determined in the range of 0.8 g/L to 9.6 g/L, being noticed that an increase in its concentration above 6.4 g/L led to worst process performances. An additional improvement was observed with the presence of iron in solution, indicating that the metal salt plays an important role in catalyzing the persulfate activation — again, an optimal iron dose was observed (80 mg/L). The combination of the three ways to activated the persulfate allowed obtaining the highest PNP (94%) and TOC (66%) removals, showing that the process is promising in the degradation of PNP and organics mineralization. Radical scavenging runs allowed concluding that both radicals, sulfate and hydroxyl, are forming during the oxidation process, however the role of SO4•− predominates. The identification and quantification of reaction intermediates was also assessed and the contribution of carboxylic acids (oxalic, maleic and pyruvic) in TOC measured was found to be higher than 95%. Finally, the effect of the matrix was evaluated, and for this purpose a domestic wastewater was spiked with 500 mg/L of PNP; it was found that the degradation of the pollutant was almost not affected by the water matrix.

Efficient removal of phenol and p-nitrophenol using nitrogen-doped reduced graphene oxide

Graphene-based materials with a conjugated π region possess unique advantages for treating wastewater contaminated with phenolic compounds. To investigate the interaction mechanisms and optimize the removal efficiency of phenol and p-nitrophenol, nitrogen-doped reduced graphene oxide (N-RGO) with an enlarged conjugated π region and increased hydrophobicity was prepared by annealing a composite of chitosan exfoliated and anchored in a graphene oxide matrix. Results showed that the equilibrium adsorption capacity of N-RGO for phenol and p-nitrophenol was 155.82 and 80.60 mg/g, respectively, at an initial concentration of 200 mg/L, pH of 6, and contact temperature of 30 °C. The optimized removal efficiency was attributed to robust π-π and hydrophobic interactions. Furthermore, regeneration experiments showed that N-RGO could retain a high removal efficiency (> 80 %) over five cycles of reuse. These findings suggest that N-RGO is a promising technique for the removal of phenolic compounds from wastewater using an efficient and recyclable adsorbent.

A Smart Adsorbent with Ability of Environmentally Friendly Regeneration for p-Nitrophenol Removal in Aqueous Solution

Every year, a large amount of waste water containing phenol derivatives is produced in industrial production, which causes serious pollution problem. In the present work, a dually photo- and thermo-responsive adsorbent was developed to remove p-nitrophenol in aqueous solution. N-isopropyl acrylamide was polymerized to build up the thermo-sensitive network of the adsorbent; and cyclodextrin/azobenzene supramolecular complex was grafted on the backbone to act as the photo-responsive adsorbing unit. Under low temperature and 365 nm irradiation, the adsorbent was found in swelling state. In this state, p-nitrophenol was easily caught and removed from aqueous solution by cyclodextrin cavities and azobenzene moieties grafted on the polymer chains. Most interesting, when irradiated at 430 nm, the inclusion of cyclodextrin cavities with azobenzene moieties let freedom of the p-nitrophenol molecules adsorbed previously; at this time if increasing the temperature up to 40 °C, the free p-nitrophenol molecules were forced out owing to the shrinkage of the poly(N-isopropylacrylamide) network. So, without any organic solvent, the adsorbent can be regenerated directly in water. It avoids the secondary pollution caused by traditional regenerating process of adsorbents with organic solvent, which is an important advantage for its practical application of the adsorbent.

Enhanced removal of p-nitrophenol by ꞵ-Ga2O3-TiO2 photocatalyst immobilized onto rice straw-based SiO2 via factorial optimization of the synergy between adsorption and photocatalysis

This work was undertaken to provide a new potent route for wastewater treatment by developing a hybrid photocatalyst from waste rice straw. On this basis, rice straw-based SiO2 was utilized as a platform to synthesize a ternary β-Ga2O3-TiO2-SiO2 nanocomposite with type-I heterojunction band alignment using the mechanochemical method. The categorical factorial design was employed to optimize the synergistic effect between adsorption and photocatalytic performance of the nanocomposite towards removing p-nitrophenol (PNP) from wastewater under various experimental conditions. The optimization results indicated the negligible impact of catalyst dose (Xc) and total dissolved solids (XTDS) on the photocatalysis with the increase of pre-adsorption time (Xads) from 60 to 180 min. In contrast, the adsorption/photocatalytic performance of ꞵ-Ga2O3-TiO2-SiO2 was found to be dependent on the solution pH (XpH, with a percentage contribution (PC) of 26.1 %) due to its effect on the photocatalyst surface charge and the dissociation process of PNP molecules. At optimum conditions (Xc = 4.0 g/L, XpH = 6.0, XTDS = 1000 mg/L, and Xads = 180 min), the β-Ga2O3-TiO2-SiO2 exhibited high efficiency to degrade 92.4 ± 3.8 % and 68.65 ± 4.3 % of PNP (25 mg/L) after 120 min UV and visible irradiation, with kinetic rates (k) of 0.62 and 0.53 mg/(g.min), respectively. This improved performance was due to the synergism between (i) the high adsorption of PNP (k = 0.017 mg/(g.min)) on SiO2 and (ii) the effective separation of photogenerated charges between ꞵ-Ga2O3 and TiO2. The high-performance stability (up to 3 cycles) of β-Ga2O3-TiO2-SiO2 was also demonstrated towards UV/visible-induced photodegradation of organic contaminants in real petrochemical wastewater.

Green synthesis of Cu nanoparticles supported on straw-graphene composite for catalytic reduction of p-nitrophenol

It is quite desired to develop an effective and cost-efficient non-noble metal catalyst for the reduction of nitrobenzene compounds. In this work, a novel and highly reactive Cu nanoparticles (CuNPs) embedded straw-graphene composite (Cu-SG) was synthesized via a facile and green one-pot hydrothermal route and then used for p-nitrophenol (PNP) reduction in the presence of NaBH4 from an aqueous medium. In comparison to the Cu-G (0.42 min−1), the Cu-SG with hierarchical pore structure and smaller CuNPs exhibited better catalytic property in PNP reduction, especially under the conditions of a mass ratio of straw-to-GO = 1 and Cu2+ ions dosage = 0.15 mmol (0.93 min−1). Interestingly, unlike Cl−, NO3− and SO42− ions, the coexisted HCO3− ions in solution could crucially accelerate the removal of PNP (1.62 min−1). This may be since HCO3− ions can both ionize and hydrolyze in water, enabling them to regulate and promote the adsorption of PNP to Cu-SG. Besides, the Cu-SG displayed good catalytic stability and can be reused for six consecutive cycles without obvious performance reduction. This study offers an insight into addressing both water pollution remediation and high-value utilization of agricultural solid waste.

Submerged membrane photocatalytic reactor for advanced treatment of p-nitrophenol wastewater through visible-light-driven photo-Fenton reactions

A submerged membrane photocatalytic reactor (SMPR) was constructed for the advanced treatment of p-nitrophenol (PNP) wastewater and rapid recycling of powdery catalyst, including a suspended photocatalytic system and a submerged microfiltration (MF) membrane system. To evaluate the performance of the SMPR, a visible-light responsive Fe(III)-ZnS/g-C3N4 photo-Fenton catalyst was successfully synthesized by the microwave hydrothermal method, and several techniques were used to characterize the resulting catalyst. The key operation factors on the wastewater treatment efficiency were successively optimized. When the influent PNP concentration was 10 mg·L−1, initial pH was 5, catalyst dosage was 1.0 g·L−1, H2O2 concentration was 170 mg·L−1, aeration rate was 0.50 m3·h−1, and operation time was 4 h, the PNP removal rate was 91.6% by the SMPR under simulated solar light irradiation. The rejection rate of the catalyst by the MF membrane was 100%, which realized the rapid separation and recycling of the suspended catalyst powders and avoided the catalyst loss and secondary pollution. The toxicity calculation results of PNP and its possible degradation products indicated that the toxicity of PNP wastewater decreased overall after the visible-light-driven photo-Fenton reactions. This study provided a combined photocatalysis-membrane filtration process that had a high treatment efficiency of refractory wastewater and solved the problem about the separation and recycling of the powdery catalyst synchronously.

Synthesis of Graphene Oxide–Supported β-Cyclodextrin Adsorbent for Removal of p-Nitrophenol

Graphene oxide–supported β-cyclodextrin was prepared with graphene oxide and β-cyclodextrin as raw materials and epichlorohydrin as crosslinking agent, respectively. It was characterized by the methods of Raman spectroscopy, FT-IR, and SEM. The graphene oxide–supported β-cyclodextrin showed excellent adsorption performance for p-nitrophenol, and the absorption equilibrium can be achieved within 2 h. The adsorptive capacity is 117.28 mg/g at adsorption temperature of 313 K and pH at 8.0. Adsorption isotherms showed that the adsorption capacity increases with the increases of temperature and adsorption process could be better fitted by Langmuir isotherm (R2 > 0.995). Thermodynamic functions (ΔG, ΔH, and ΔS) investigation showed that the adsorption is spontaneous, endothermic, and random. The adsorption kinetics of p-nitrophenol over graphene oxide–supported β-cyclodextrin is conformed to a pseudo-second-order process. This study has suggested that the graphene oxide–supported β-cyclodextrin could play an efficient and beneficial source of the adsorbent for the purpose of eliminating p-nitrophenol from aqueous solution.

Magnetic ZnO@Fe3O4 composite for self-generated H2O2 toward photo-Fenton-like oxidation of nitrophenol

The present work focuses on the synthesis of a magnetically separable and stable catalyst for self-supplying H2O2 in photo-Fenton degradation of p-nitrophenol. Different from the most popular Fe3O4@ZnO core-shell structure, ZnO microflower cores were partially wrapped with Fe3O4 nanoparticles via a layer-by-layer self-assembly process. Several characterisation techniques were employed to investigate the crystal structure, morphology, surface chemistry and optical properties of the produced composites. The band gaps of the ZnO and Fe3O4 were considerably decreased from 3.05 to 2.60 to 2.35 eV after the assembly. The optimum Fe3O4 deposition layer number was found to be 5 for achieving 100% p-nitrophenol removal in 60 min. The degradation was triggered with in-situ photocatalytic formation of hydrogen peroxide over Fe3O4@ZnO. The exposed Fe3O4 nanoparticles provided Fe2+ and Fe3+ Fenton-active species for stable operation. We explored possible mechanisms of the enhanced photocatalysis by quenching and radical trapping experiments. The magnetic separation was also performed to recover and reuse the spent catalyst.

Using ultrasonic treated sludge to accelerate pyridine and p-nitrophenol biodegradation

Aerobic biomass (acclimated activated sludge) was treated by ultrasound and used to accelerate biodegradations of pyridine and p-nitrophenol (PNP), which begin with mono-oxygenation reactions that need an internal electron donor. Ultrasound treatment disrupted the biomass and produced more soluble and (especially) colloidal organic material. Compared with untreated biomass, pyridine- and PNP-biodegradation rates increased when treated biomass provided electron donor. Pyridine- and PNP-biodegradation rates increased by 10% and 20%, respectively, over the control experiments when supernatants from treated biomass were added into the medium. For accelerating pyridine- and PNP removal rates, adding supernatants of treated biomass was equivalent to adding succinate of 0.35 mmol/L and 0.21 mmol/L, respectively. The rates were increased by 63% for both substrates when the entire treated biomass was added. Colloidal solids in the treated biomass contained most of biodegradable electron donor able to stimulate initial monooxygenations of pyridine and PNP. Adding treated biomass together with untreated biomass gave a synergistic impact on enhancing pyridine and PNP biodegradation, because the treated biomass supplied extra donor, while the untreated biomass maintained a high level of active biomass.

Activated carbon/MOFs composite: AC/NH2-MIL-101(Cr), synthesis and application in high performance adsorption of p-nitrophenol

P-nitrophenol (PNP), a hazardous phenolic material, should be eliminated from water in order to prevent damage to the marine ecosystem, animals as well as humans. Although adsorption seems to become the most widely used strategy, an effective and strong-capacity adsorbent to minimize PNP under the approved concentration is essential to discovering. In this study, a class of porous adsorbents composite was developed for the PNP removal from water. AC-NH2-MIL-101(Cr) has chosen to boost the removal of PNP from water owing to extremely porous and stable in water. The fabricated composite has 2049 m2.g−1 large surface area and 0.93 cm3.g−1 pore volume. The adsorption kinetics and isotherms were investigated. AC-NH2-MIL-101(Cr) was found to exhibit an adsorption capacity of ~ 18.3 mg g−1. The mechanism for this strong adsorption performance was suggested and related to affinity NO2 groups of PNP and the unsaturated chromium site of AC-NH2-MIL-101(Cr), the coulombic interaction via the hydrogen bond between the PNP and AC-NH2-MIL-101(Cr) and π-π stacking interaction. AC-NH2-MIL-101(Cr) composite also displayed exceptional stability and reusability after a successive PNP removal processes. This study provides new insight into developing and synthesizing extremely effective nanoporous material for organic contaminants disinfection from waste water based on MOFs.

Coupling adsorption and degradation in p-nitrophenol removal by biochars

Biochar is an attractive class of materials because of its various feedstock and wide application potential in agricultural and environmental remediation activities. Recent studies have suggested that biochar may both adsorb and degrade organic contaminants; however, the properties of biochar that control its apparent interactions with organic contaminants are still unknown. In this study, p-nitrophenol was chosen as a model organic pollutant. Its adsorption and degradation by biochar were investigated with a special focus on correlations with the biochar properties. The apparent removal of p-nitrophenol by biochars increased with the increase of pyrolysis temperature. After acetonitrile extraction of the biochars, p-nitrophenol adsorption increased while degradation decreased. Thus, there was no significant change in the apparent removal of p-nitrophenol across eight reaction cycles. An analysis of the physicochemical properties of biochar showed that p-nitrophenol adsorption was determined by the biochar surface area, while the degradation may be because of the varying compositions of biochars, including free radicals, functional groups determining its redox activities, and transition metals. The relative importance of these compositions varied with the pyrolysis temperature. More extensive study is warranted on the relationship between biochar properties and reactivity for targeted biochar production and application. The results of this study provide fundamental information on biochar preparation and its application in organic pollutant removal.

Hydrogel-rice husk biochar composite as an adsorbent for the removal of phenol and PNP from aqueous solutions

ABSTRACT Poly(acrylamide)-rice husk biochar [p(AAm)-RHB] hydrogel composites (HBC-RH) were used to eliminate phenols. The characterization of prepared composite was investigated by using SEM, TEM, TGA DSC, and FTIR. Based on our findings, the highest removal of phenol and p-nitrophenol (PNP) was found as 82.2% and 84.6% in 50 mg/L solution at pH = 7, respectively. The results revealed that the kinetic data were best fitted by pseudo-first-order for phenol and pseudo-second-order for PNP. To be concluded that the Temkin model perfectly described the removal of phenol and HBC-RH can be widely applied for various containments.

Magnetic cross-linked chitosan modified with ethylenediamine and β-cyclodextrin for removal of phenolic compounds

The Fe/CLCh-EDA/β-CD adsorbent was prepared using cross-linked chitosan (CLCh) containing magnetic iron oxide and modified with ethylenediamine (EDA) and β-cyclodextrin (β-CD). This adsorbent was characterized by infrared (IR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, Atomic Absorption Spectroscopy (EAA), Scanning Electron Microscopy (SEM), zeta potential and elemental analysis (CHN). The effect of adsorbent dosage, contact time, pH, kinetics, temperature and adsorption thermodynamics were evaluated by the removal of phenol (PHE), p-nitrophenol (PNP) and p-cresol (PCS). The Fe/CLCh-EDA/β-CD presented a maximum adsorption capacity for PHE of 243.08 mg g−1, PNP of 274.24 mg g−1 and PCS of 298.35 mg g−1 (120 min) at pH 6 and 25 °C. The Fe/CLCh-EDA/β-CD can be easily removed from the aqueous solution by magnetization due to its magnetic properties. Thermodynamic parameters indicate that adsorption is spontaneous and exothermic. This adsorbent showed satisfactory results when applied in the treatment of pulp and paper industry effluent that naturally contains phenol, p-nitrophenol and p-cresol and fortified river water samples.

Activated H2O2 on Ag/SiO2–SrWO4 surface for enhanced dark and visible-light removal of methylene blue and p-nitrophenol

Abstract Activated H2O2 on the surface of nanostructures for advanced oxidation process attracts the interest for energy consumption, time saving rather than Fenton reaction process. Here, we introduce Ag/SiO2 NPs immobilized on SrWO4 surface for enhanced catalytic and photocatalytic oxidation of methylene blue and reduction of p-nitrophenol by H2O2 surface activation. Both theoretical calculations (rwb97xd/LANL2DZ) and experimental (FT-IR and XRD) show that the catalytic enhancement was due to the surface interaction between Ag/SiO2 and SrWO4 that activate H2O2 surface molecules in absence of light. The photocatalytic enhancement was interpreted by the hot electrons ejected from Ag NPs to the SrWO4 rather than the p-n junction created by Ag/SiO2 and SrWO4 mechanism. Different spectroscopic techniques such as SEM, TEM, XRD were used for the catalysts characterizations. The optical measurements such as UV–Vis and photoluminescence were incorporated to further support the mechanism. The catalyst posses high catalytic activity over wide pH range (4–10).