Mineralization Of P-nitrophenol Research Articles

Ultrasonic synthesis of Graphite/C, N co-doped TiO2 nanocomposite as an efficient and durable photocatalyst for the degradation and mineralization of p-nitrophenol

P-nitrophenol (PNP) as an industrial waste effluent is present in many industries, including the dye and textile industries and tanneries, and is the cause of severe human and environmental health risks. In the present study, a facile, effective, and innovative sonochemical procedure was developed at low frequency (20 kHz) and room temperature for the synthesis of graphite (G)/C, N co-doped TiO2 nanocomposite. Herein, tetra n-butyl orthotitanate as the titanium precursor, graphite as the C, and NH4Cl as the N sources were applied in the synthesis of the nano-photocatalyst. The effect of the molar ratio of N/TiO2 was studied in the synthesis of G/C, N co-doped TiO2 nanocomposite. Various techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM), High-resolution microscopy (HRTEM), X-ray Photoelectron Spectroscopy (XPS), photoluminescence (PL), Brunauer–Emmett–Teller (BET), Elemental and Mapping analyses (EDS) and UV/Vis diffuse reflectance (UV/vis DRS) were used to characterize the nanocomposite. The results also showed that ultrasound decreased the particle size and improved the size distribution. DRS results showed a narrower band-gap and a red shift of light absorption edge for G/C, N co-doped TiO2 nanocomposite compared to TiO2. The data obtained from XPS established the presence of C, N, Ti, and O elements in the nanocomposite. In addition, the efficiency of the photo-catalytic performance of the nanocomposite was assessed using the pollutant PNP. The fabricated nanocomposite presented photo-catalytic activity much more than TiO2 in PNP degradation with an efficiency of 100 % within 70 min under the illumination of 400 W Xe light. The extraordinary activity of nanocomposite concerning TiO2 was mostly attributed to its high crystallinity, strong visible light absorption, and the impressive separation of photo-induced charge carriers. The radicals in the charge of destruction process were checked via the scavenging tests. The results confirmed that °O2− radical had a basic role in the process of photo-catalytic and an acceptable mechanism was proposed for the photo-catalytic degradation.

Encapsulating Fe-Co bimetal inside carbon aerogel to boost electron transfer for efficient heterogeneous electro-peroxone oxidation of organic pollutants

We fabricated a novel Fe-Co bimetal encapsulated inside carbon aerogel sphere (Fe2Co@CS) to improve the electro-peroxone (EP) process. The degradation and mineralization of p-nitrophenol (p-NP) were 100% (15 min) with rate constant of 0.314 min−1 and 83.8% (60 min) in Fe2Co@CS/EP, respectively. Fe2Co@CS was composed of defective graphite carbon and Fe2Co alloy. The presence of metal–oxygen-carbon (M-O-C, MFe/Co) bonds promoted interface electron transfer from carbon layer towards Fe2Co alloy, which was advantageous to the reduction of ≡Fe3+/≡Co3+. Moreover, the Fe-Co synergistic effect also accelerated the interfacial catalytic reaction for activating O3 and H2O2. The quenching experiment and EPR test indicated that ·OH, ·O2- and 1O2 were main reactive oxygen species (ROSs). DFT calculations showed that O3 had lower adsorption energy on Fe2Co@CS than H2O2, manifesting that catalytic ozonation played the key role in ROSs generation. In addition, ozone utilization efficiency in Fe2Co@CS/EP (ΔTOC/ΔO3 = 1.23–0.68) revealed 66-36% increase relative to those of EP (0.74–0.5). Fe2Co@CS was an efficient catalyst over a wide pH range (3–11) with permissible iron and cobalt releases. The Fe2Co@CS/EP process exhibited high-performance for degrading different pollutants under high salinity condition with coexistence of Cl−, NO3− and SO42−. For treating real coal wastewater, the TOC removal was 52.7% at 4 h with low EEC (0.038 kWh (g TOC)−1). This study provided an efficient method for the development of EP in wastewater treatment.

Sequentially modified carbon felt for enhanced p-nitrophenol biodegradation through direct interspecific electron transfer

The widely applied aromatic nitration in modern industry leads to toxic p-nitrophenol (PNP) in environment. Exploring its efficient degradation routes is of great interests. In this study, a novel four-step sequential modification procedure was developed to increase the specific surface area, functional group, hydrophilicity, and conductivity of carbon felt (CF). The implementation of the modified CF promoted reductive PNP biodegradation, attaining 95.2 ± 0.8% of removal efficiency with less accumulation of highly toxic organic intermediates (e.g., p-aminophenol), compared to carrier-free and CF-packed biosystems. The constructed anaerobic-aerobic process with modified CF in 219-d continuous operation achieved further removal of carbon and nitrogen containing intermediates and partial mineralization of PNP. The modified CF promoted the secretion of extracellular polymeric substances (EPS) and cytochrome c (Cyt c), which were essential components to facilitate direct interspecies electron transfer (DIET). Synergistic relationship was deduced that glucose was converted into volatile fatty acids by fermenters (e.g., Longilinea and Syntrophobacter), which donated electrons to the PNP degraders (e.g., Bacteroidetes_vadinHA17) through DIET channels (CF, Cyt c, EPS) to complete PNP removal. This study proposes a novel strategy using engineered conductive material to enhance the DIET process for efficient and sustainable PNP bioremediation.

Effective mineralization of p-nitrophenol in water by heterogeneous catalytic ozonation using Ce-loaded sepiolite catalyst

Clay-based composite materials have been widely used for environmental remediation due to their excellent physicochemical properties, however, there are few studies on clay-based composite materials as ozone catalyst carriers. In this study, Ce-loaded sepiolite (Ce/SEP) catalyst was synthesized using an impregnation-calcination method. Ce/SEP catalysts had a higher efficiency for heterogeneous catalytic ozonation than sepiolite alone. Among different mass ratios of Ce element to sepiolite (5 % Ce/SEP, 7 % Ce/SEP, 10 % Ce/SEP, and 15 % Ce/SEP), 10 % Ce/SEP showed the best catalytic performance with the mineralization efficiency of p-nitrophenol (PNP) as 71 % that was 1.15, 1.08, and 1.18 times higher than that of 5 % Ce/SEP, 7 % Ce/SEP, and 15 % Ce/SEP, and increased by 30 % compared to that of the ozonation alone. Larger surface area and abundance of strong acid sites of Ce/SEP favored adsorption of ozone molecules on the catalyst surface. High content of oxygen vacancies in the catalyst promoted Ce3+/Ce4+ cycling and subsequently a superior catalytic activity of the Ce/SEP catalyst. In addition, free radical quenching experiments as well as electron spin resonance analysis indicated that hydroxyl radical (∙OH) was the main contributor to the mineralization of PNP in this system. This study provides a novel strategy for the heterogeneous catalytic ozonation of refractory organic pollutants in water.

Effective mineralization of p-nitrophenol by catalytic ozonation using Ce-substituted La1‒xCexFeO3 catalyst

In this study, cerium-doped lanthanum ferrite perovskite oxides (La1‒xCexFeO3) with different A-site were synthesized using a sol-gel method and they were used as ozonation catalyst for p-nitrophenol (PNP) mineralization for the first time. Catalytic activity in terms of total organic carbon (TOC) removal followed the order of La0.8Ce0.2FeO3 > La0.4Ce0.6FeO3 > La0.6Ce0.4FeO3 > La0.2Ce0.8FeO3 > LaFeO3 with 77, 66, 61, 60 and 56% respectively. The synthesized catalysts were characterized by diffraction of X-ray (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) and scanning electronic microscopy (SEM). Moreover, electron spin resonance (ESR) and radicals quenching experiments showed that the active oxygen species in the ozone decomposition process are mainly hydroxyl radical (·OH), and also include superoxide radical (O2−) and singlet oxygen (1O2). Furthermore, the superior activity of La0.8Ce0.2FeO3 could be attributed to the higher surface area, the richer lattice oxygen, richer surface –OH groups and the facilitated redox Ce3+/Ce4+ and Fe2+/Fe3+ cycling. In addition, this study provides an insight to use metal-doped perovskite catalysts for catalytic ozonation.

Novel Fe0-C/S(IV) system: Toward the interaction between Fe0-C internal electrolysis and sulfite for p-nitrophenol degradation

In this study, an innovative redox system concerning Fe0-C internal electrolysis combined with sulfite (S(IV)) was first developed for p-nitrophenol (PNP) removal. The effects of different influencing factors including the Fe0/C mass ratio, sulfite concentration, initial pH value and aeration rate were comprehensively investigated in batch experiments. Satisfactorily, the maximum removal and mineralization of PNP reached 92.5% and 59.9%, respectively, in the Fe0-C/S(IV) system. Fe0-C composites with nanosized zero-valent iron anchored on activated carbon had great potential to release Fe2+ and initiate the activation of S(IV). During the reactions, transformation from Fe3+ to Fe2+ was realized, which was attributed to complexation. Significantly, the surface complexation occurred in the diffusion boundary because of the active iron species (Fe(II)–OH) generated on Fe0-C composites, having a remarkable activation effect on S(IV). Furthermore, the reactivity of Fe0-C composites was maintained through the associated effects of the complexation, acid etching and oxidation erosion caused by S(IV). In the end, quenching and ESR experiments illustrated that HO and SO4− were the dominant free radicals, combined with the subordinate participation of SO3− and SO5−. Reduction and oxidation collaborated efficiently to degrade PNP, and Fe0-C internal electrolysis and S(IV) mutually promoted each other in the process, which fully motivated strong the potential of this Fe0-C/S(IV) system to deal with toxic and refractory wastewater.

Unraveling Kinetic Effects during Photoelectrochemical Mineralization of Phenols. Rutile:Anatase TiO2 Nanotube Photoanodes under Thin-Layer Conditions

The kinetics of the photoelectrochemical mineralization of p-nitrophenol (PNP) and p-methoxyphenol (PMP) on rutile:anatase TiO2 nanotube electrodes (% rutile: 0, 16, and 20) has been studied. Oxida...

Co3O4/Bi4O5I2/Bi5O7I C-Scheme Heterojunction for Degradation of Organic Pollutants by Light-Emitting Diode Irradiation.

Remediation of organic pollutant matrixes from wastewater by photodegradation using different heterojunctions is extensively studied to improve performance for potential application. Brilliant black (BB) and p-nitrophenol (PNP) have been detected in the environment and implicated as directly or indirectly carcinogenic to human health. This work analyzes their elimination from aqueous solutions under visible-light irradiation with composites of cobalt(II, III) oxide and bismuth oxyiodides (Co3O4/Bi4O5I2/Bi5O7I). The synthesized nanomaterial properties were investigated using various techniques such as BET, SEM/EDS, TEM, XRD, FTIR, PL, and UV–vis. All the nanocomposites absorbed in the visible range of the solar spectrum with band gaps between 1.68 and 2.79 eV, and the specific surface area of the CB2 composite increased by 35.8% from that of Bi4O5I2/Bi5O7I. There was an observed massive reduction in the rate of electron and hole recombination, and the band gaps of the composites decreased. The mineralization of PNP and BB was followed by determination of the total organic carbon with reductions of 93.6 and 83.7%, respectively. The main active species were the hydroxyl radicals, while the superoxide anion radical and generated holes were minor as confirmed by radical trapping experiments. The optimum pHs for degradation of PNP and BB were 9.6 and 5.3, respectively. The enhanced performance of the catalyst was due to C-scheme heterojunction formation that reduced the electron and hole recombination rate and was attributed to strong adsorption of the pollutants on the photocatalyst active surface. The nanocomposite is apposite for solar energy-driven remediation of organic pollutants from environmental aqueous samples.

Chemical state and coordination structure of La cations doped in KTaO3 photocatalysts

We here dope KTaO3 with La through a solid-state route, resulting in enhanced photocatalytic activity for the mineralization of p-nitrophenol under UV light. We suggest simultaneous substitution of K and Ta by La, leading to lattice expansion and surface nanosteps. With increasing the La concentration, the conduction band edge is raised, while the valence band remains unchanged. As a result, the band gap increases. The raised conduction band edge is proposed to be the key behind the enhanced photocatalytic activity since it results in an increased reduction power of photoproduced electrons. The raised conduction band edge is also an indication of the substitution of Ta, which mainly makes up the conduction band, by La. Furthermore, X-ray photoelectron spectroscopy and X-ray absorption near edge structure confirm the oxidation state of La residing on the surface and in the bulk to be +3, as anticipated. Extended X-ray absorption fine structure then confirms that increasing the La concentration slightly increases the length and the coordination number of La-O bond in the here prepared La-doped KTaO3. The increased bond length is due to the expanded lattice, while the increased coordination number is due to the increased numbers, and hence the contributions, of La-O pairs.

Photo-decontamination of p-nitrophenol using reusable lanthanum doped ZnO electrospun nanofiber catalyst

P-nitrophenol is a common persistent pollutant present in industrial waste water. Photocatalytic degradation of organic pollutants is an efficient method of detoxification that has been well established. This study investigates the novel method of photocatalytic degradation using Lanthanum doped zinc oxide nano rods synthesized by hydrothermal technique and impregnated on PAN nanofiber (La doped ZnO NF). The functionalized La doped ZnO nanofiber was characterized by XRD, SEM, TEM and STA. The residual concentration and mineralization of p-nitrophenol were assessed using UV–Vis spectrophotometer and Total organic carbon analyzer. The catalytic properties remained unchanged even after multiple cyclesof degradation. Repeat cycles of remediation showed consistent efficiency rate of 92% proving its cost-effectiveness and viability. The photocatalytic performance of La doped ZnO NF was investigated on p-nitrophenol in optimized experimental conditions. The process may be an economically viable process for upscaling photocatalytic degradation processes.

Nano CuO immobilized fly ash zeolite Fenton-like catalyst for oxidative degradation of p-nitrophenol and p-nitroaniline

Catalytic wet peroxide oxidative degradation of p-nitrophenol (PNP) and p-nitroaniline (PNA) in aqueous solution was studied using coal fly ash converted and nano CuO fringes incorporated zeolite X material (CuO/FAZ). CuO/FAZ was synthesized by ion exchange with Cu2+, and subsequent calcination of zeolite. The effect of various parameters such as CuO loading, H2O2 concentration, catalyst dosage, initial concentration of PNP or PNA and pH was investigated. Under the optimal condition (catalyst dose 500mg/L, 20ppm PNP and PNA, pH=6.5, 2mL H2O2, room temperature) the% degradation of PNP and PNA was about 96 and 84 for 180min reaction time respectively. The reaction intermediates were analyzed by HPLC-(-ESI)-TOF-MS spectroscopy whose result indicated the complete mineralization of PNP and PNA. Concludingly, nano CuO immobilization into FAZ and the synergic effect between them greatly improved the catalytic activity of CuO/FAZ. Hence CuO/FAZ emerged as a novel, stable, reusable heterogeneous Fenton-like catalyst. Through wet catalytic degradation of PNP or PNA, this work not only provides environmental remediation solution to such toxic pollutants, but also to the solid pollutant coal fly ash through its conversion into an efficient zeolite catalyst.

Degradation of nitro-aromatic explosives using recyclable magnetic photocatalyst: Catalyst synthesis and process optimization

In this research, degradation of P-Nitrophenol (PNP) as a model nitro-aromatic compound was carried out by photocatalytic process using magnetic Titania nano particles (MTNPs). The recyclable MTNPs were synthesized with average diameter of 22nm and a narrow size distribution. The process was modeled and optimized by a second order reduced polynomial model. Based on the model prediction, the process can be degraded PNP up to 90% under the optimum conditions of the initial pH=4, [PNP]=15mgL−1, [MTNPs]=85mgL−1, and T=25°C. PNP mineralization was obtained 69%, at the optimum condition after 120min of the process. The process kinetic was well fitted by pseudo first order kinetic model and electrical energy consumption of the process was obtained about 177.8kWh/m3. Furthermore, the effect of sodium sulfite, sodium sulfate and sodium nitrite on the photocatalytic degradation process was assessed. The results showed that sulfite or sulfate ions decrease and nitrite ions increase the process efficiency. Also, a sample of redwater as a nitro-aromatic effluent was treated.

Influence of Temperature on the Removal of Extremely High Concentration p‐Nitrophenol Simulated Wastewater by Fe/Cu/H2O Systems

In this study, the effect of the operating temperature on the removal of high p‐nitrophenol (PNP) concentrations by Fe/Cu/H2O systems has been investigated thoroughly. The results suggest that only a higher operating temperature (>40°C) could significantly improve the removal efficiency of high PNP concentrations (e.g. 10 000 mg/L) by Fe/Cu/H2O systems. Meanwhile, a lower PNP concentration (e.g. 500 mg/L) could be completely removed by Fe/Cu/H2O systems only at 40°C. Furthermore, the interaction between the operating temperature (10–85°C) and other key operating parameters including theoretical Cu mass loading (0–0.89 g Cu/g Fe), Fe/Cu dosage (5–35 g), stirring speed (0–400 rpm), electrolyte (0–50 mmol/L NaCl or Na2SO4), and initial pH (3.–12) was investigated, respectively. In particular, the elevating temperature could decrease theoretical Cu mass loading, Fe/Cu dosage, stirring speed and electrolyte, and abroad the range of initial pH, which could reduce the operating cost of Fe/Cu/H2O systems if the waste‐heating vapor could be used to elevate the operating temperature. According to the results of UV‐Vis spectra, for total organic carbon and chemical oxygen demand, it is clear that the elevating temperature could facilitate mineralization of PNP in an aqueous solution by Fe/Cu/H2O systems. As a result, the operating temperature was a main factor for the removal of pollutants by Fe/Cu/H2O systems.

Optimization of gas–liquid hybrid pulsed discharge plasma for p-nitrophenol contaminated dredged sediment remediation

p-Nitrophenol (PNP) removal in dredged sediment during pulsed discharge plasma process was studied in terms of adjustable trim capacitance, electrode distance and gas-flow rate. PNP degradation efficiency reached up to 88.5% under the conditions of adjustable trim capacitance of 2.0 nF, electrode distance of 16 mm, and air flow rate of 0.8 L min−1. To a certain extent, increasing the adjustable trim capacitance and decreasing the electrode distance leaded to high PNP degradation efficiency. An appropriate air flow rate was determined for gaining relatively high PNP removal efficacy. PNP mineralization was analyzed by UV–Vis spectrum, COD, and TOC evolution.

Investigation of the synergistic effects for p-nitrophenol mineralization by a combined process of ozonation and electrolysis using a boron-doped diamond anode

Electrolysis and ozonation are two commonly used technologies for treating wastewaters contaminated with nitrophenol pollutants. However, they are often handicapped by their slow kinetics and low yields of total organic carbon (TOC) mineralization. To improve TOC mineralization efficiency, we combined electrolysis using a boron-doped diamond (BDD) anode with ozonation (electrolysis-O3) to treat a p-nitrophenol (PNP) aqueous solution. Up to 91% TOC was removed after 60min of the electrolysis-O3 process. In comparison, only 20 and 44% TOC was respectively removed by individual electrolysis and ozonation treatment conducted under similar reaction conditions. The result indicates that when electrolysis and ozonation are applied simultaneously, they have a significant synergy for PNP mineralization. This synergy can be mainly attributed to (i) the rapid degradation of PNP to carboxylic acids (e.g., oxalic acid and acetic acid) by O3, which would otherwise take a much longer time by electrolysis alone, and (ii) the effective mineralization of the ozone-refractory carboxylic acids to CO2 by OH generated from multiple sources in the electrolysis-O3 system. The result suggests that combining electrolysis with ozonation can provide a simple and effective way to mutually compensate the limitations of the two processes for degradation of phenolic pollutants.

Catalytic ozonation of p-nitrophenol over mesoporous Mn–Co–Fe oxide

Mesoporous composite metal oxides were prepared by an oxidation–precipitation method. The characterization studies indicated that the structure and surface property of the products could be controlled through simple manipulation of precursor composition. The activity of the synthesized catalysts for ozonation of p-nitrophenol (PNP) in aqueous solution was investigated. It was found that the negatively charged surface enhanced the adsorption and decomposition of ozone, but inhibited the adsorption of organic intermediates. This heterogeneous catalytic ozonation process should mainly follow a mechanism of surface reactions involving adsorbed ozone and organic molecules. Mn–Co–Fe exhibited the highest catalytic activity and stability for the mineralization of PNP due to its proper adsorption capacities for ozone and organic intermediates, which facilitated the surface reactions.

Evaluation and optimization of multi-channel pulsed discharge plasma system for soil remediation

Pulsed discharge plasma is a rapid and high-efficient option for organic pollutants contaminated soil remediation. In order to optimize the coupling of pulsed power supply and plasma reactor, and enhance pollutant removal in soil by pulsed discharge plasma, power circuit parameters and reactor configuration such as adjustable trim capacitance, discharge needle number, and discharge voltage were optimized with respect to energy input, power source efficiency, pollutant degradation, process efficiency, and energy yield. p-Nitrophenol (PNP) was chosen as the model pollutant in soil. The experimental results showed that 90.7% of PNP were degraded under the conditions of adjustable trim capacitance 200 pF, discharge needle number 19, and discharge voltage 18.0 kV, with power source efficiency of 62.5%. The increase of adjustable trim capacitance was beneficial for PNP degradation and process efficiency, but not for power source efficiency and energy yield. Higher PNP degradation efficiency was obtained as more discharge needle numbers were employed, as well as for the power source efficiency and energy yield. Increasing discharge voltage benefited PNP degradation, but went against energy yield. The power source efficiency increased firstly with discharge voltage, and then decreased with further increasing discharge voltage. Furthermore, PNP mineralization was also analyzed.

Depth dependence of p-nitrophenol removal in soil by pulsed discharge plasma

A series of soil column experiments were performed to investigate p-nitrophenol (PNP) degradation and active species diffusion behaviors in soil layers during pulsed discharge processes. The effects of organic matter, metal oxides, soil moisture, discharge voltage, treatment time, and pollutant concentration on PNP degradation and active species transport were evaluated. PNP degradation efficiency was inversely proportional to organic matter content, due to its adsorption for PNP and blocking for active species transport. For layer 0–2mm, 99.2% of PNP was removed after 45min of discharge treatment in column packed with quartz sand, followed in descending order, by sand (85.0%), by sandy soil (77.9%), and by clay soil (61.9%). Metal oxides affected PNP degradation through catalyzing ozone decomposition. Moist soil, higher discharge voltage, and lower PNP initial concentration benefitted active species diffusion and thus promoted PNP degradation. PNP degradation processes in soil layers followed first-order kinetic model, and the reaction rate constant decreased from 0.0458min−1 in soil layer 0–2mm to 0.0078min−1 in soil layer 10–12mm. PNP mineralization and degradation intermediates were also identified in soil layers. The distribution of intermediates in soil layers confirmed the different diffusion behaviors of active species.

Electro-Fenton degradation of p-nitrophenol using the anodized graphite felts

A simple and efficient electrochemical oxidation method was used to modify the graphite felts. A remarkable change on the surface chemistry was observed by the X-ray photoelectron spectrum analysis. The modified electrodes were found having much higher electrocatalytic activity toward oxygen reduction reaction than the pristine one, and thus, the in situ production of H2O2 and the enhanced decontamination efficiency in Electro-Fenton (EF) system. The accumulation of H2O2 at the optimal modified electrode was as about 2.7 times as the pristine one. After optimizing the operational parameters such as Fe3+ concentration, potentials, pH and O2 flow rate, the mineralization of p-nitrophenol could be above 78%. It can be expected to perform the EF system under these optimal conditions to improve treatment efficiency.

Photocatalytic degradation of p-nitrophenol by zinc oxide particles

The degradation of p-nitrophenol (PNP) by ZnO particles has been studied. With increasing PNP loading the degradation rate decreased. The mineralization of PNP was rather slow compared with the degradation. With a decrease in particle diameter or an increase in surface area, the degradation rate significantly increased. The degradation capability with solar irradiation was found to be superior to UV light irradiation. It was found that 30 mg L(-1) of PNP was completely degraded by solar light with the accumulated UV light of around 23 kJ L(-1) at ZnO dosage of 5 g L(-1). The degradation PNP by ZnO with UV light or solar light was faster than that by TiO(2).