P-nitrophenol Removal Efficiency Research Articles

CuFe2O4 as heterogeneous catalyst in degradation of p-nitrophenol with photoelectron-Fenton-like process

In this research, the heterogeneous photoelectron-Fenton-like process using copper ferrite (CuFe2O4) as catalyst was employed to remove p-nitrophenol (PNP). The CuFe2O4 catalyst was prepared by a co-precipitation process and characterised with X-ray fluorescence analysis, X-ray diffraction analysis and BET surface area. The results confirmed that CuFe2O4 was prepared successfully. Under the optimum conditions, namely 0.05 mol L−1 Na2SO4, the electrical potential of −0.6 V, pH 3.0 and 0.067 g L−1 CuFe2O4, 92.8% of 0.1 mM L−1, the PNP removal efficiency could reach 92.8% for 0.1 mM L−1 PNP after 180-min treatment. This technology can be applied for the treatment of organic compounds which are not readily biodegradable.

Removal and Adsorption of p‐Nitrophenol from Aqueous Solutions Using Carbon Nanotubes and Their Composites

In an attempt to explore the possibility of using carbon nanotubes (CNTs) as efficient adsorbents for removal of pollutants from the contaminated water, the adsorption of p‐nitrophenol (PNP) on raw multiwalled carbon nanotubes (r.MWNTs) with different outer diameters, various functionalized multiwalled carbon nanotubes (f‐MWNTs), raw single‐walled carbon nanotubes (r.SWNTs) and oxidized single‐walled carbon nanotubes (ox‐SWNTs) has been investigated. The ox‐SWNTs showed better adsorption ability for PNP with different concentrations, while lower uptake capacity was found for all of the r.MWNTs and f‐MWNTs. The removal efficiency of PNP by ox‐SWNTs was around 98%, indicating that ox‐SWNTs possess a great potential application prospect for removing PNP from aqueous solutions.

BIOREMEDIATION CONTAINING WASTEWATER BY OF P-NITROPHENOL AEROBIC GRANULES

Aerobic granulation is a novel biotechnique for the treatment of coloured wastewater containing toxic xenobiotics in sequencing batch reactor (SBR). The aerobic granules were investigated as a potential biomaterial for biodegradation of p-nitrophenol. The removal efficiency of p-nitrophenol was 93 % after 65 days of operation at 8 hr hydraulic retention time (HRT). The aerobic granules were cultivated at a p-nitrophenol loading rate of 0.9 kg m-3 day-1, with sodium acetate as co-substrate to accelerate the growth of p-nitrophenol degrading biomass. SBR was inoculated with activated sludge that was initially conditioned as a batch culture for a period of 30 days by supplying p-nitrophenol. Optimal pH of 9 was maintained throughout the experimental setup. This study clearly demonstrates that aerobic granules are efficient to degrade up to 300 mgL-1 of p-nitrophenol to tolerate the toxicity in high-strength wastewater.

Removal of p-nitrophenol (PNP) in aqueous solution by the micron-scale iron–copper (Fe/Cu) bimetallic particles

In this study, in order to further investigate the degradation capacity and mechanism of Fe/Cu bimetallic system, the prepared Fe/Cu bimetallic particles with different theoretical copper mass loadings (0.05, 0.11, 0.24, 0.41, 0.62, 0.89, 1.26 and 1.81gCu/gFe) were characterized by SEM, EDS, XRD and laser particle size analyzer. Also, the effect of theoretical Cu mass loading and five key operating parameters on the PNP removal efficiency was investigated thoroughly. Furthermore, the mineralization process of PNP was studied by using COD, TOC, UV–vis spectra, FTIR spectra and GC/MS. The results show that a large number of fine Cu particles were produced from the excessive theoretical Cu mass loading, and they facilitated the catalytic reactivity of the Fe/Cu bimetallic particles at Cu loading <0.89gCu/gFe. Additionally, the heterogeneous Cu layer is also favor for the catalytic reactivity of the Fe/Cu bimetallic particles, while the uniform and dense Cu layer can decrease its reactivity severely. The degradation rates of PNP by the Fe/Cu particles with different theoretical Cu mass loadings are all in accordance with the pseudo-first-order kinetics model, and the optimal operating parameters were obtained by the batch experiments. In addition, both the indirect reduction by atomic hydrogen and the direct reduction on the catalytic activity sites play a leading role on the pollutants removal. Finally, the degradation pathway of PNP was proposed according to the detected intermediates by GC/MS. Collectively, these results suggest that the Fe/Cu bimetallic system should be proposed as a cost-effective pretreatment process for the toxic and refractory PNP wastewater.

Removal of high concentration p-nitrophenol in aqueous solution by zero valent iron with ultrasonic irradiation (US–ZVI)

In this study, the US–ZVI system was used to produce the strong reductants including H and nascent Fe2+ ions to eliminate the toxicity of the high concentration p-nitrophenol (PNP) wastewater. The effect of the reactor structure, initial pH, ZVI dosage, ultrasonic power and initial PNP concentration on the removal efficiency of PNP from water was investigated intensively. The results show that a higher removal rate can be obtained by using a conical structure reactor, and the lower initial pH can aid the acceleration of PNP removal rate by using US–ZVI system. Furthermore, the removal efficiencies of PNP increased obviously with the increase of initial ZVI concentration from 0 to 15gL−1. Also, the treatment capacity of ZVI was enhanced remarkably by the ultrasonic irradiation, and the US–ZVI system can maintain high treatment efficiency for the high concentration PNP wastewater (500–10,000mgL−1). Meanwhile, the high removal efficiency of PNP was mainly resulted from the synergistic reaction of ZVI and US. At last, the main degradation product (i.e., p-aminophenol) was detected by gas chromatography–mass spectrum (GC–MS). Thus, the reaction pathway of PNP in the US–ZVI system is proposed as a reducing process by the H and nascent Fe2+ ions.

P‐nitrophenol toxicity to and its removal by three select soil isolates of microalgae: The role of antioxidants

The nontarget effects, in terms of biochemical changes induced by p-nitrophenol (PNP) in three soil microalgae, Chlorella sp., Chlorococcum sp., and Heterochlamydomonas sp., and the PNP removal efficiency of these isolates, were determined. On exposure to 20 mg L(-1) PNP, Chlorella sp. showed greater activity of peroxidase, superoxide dismutase, and glutathione reductase as well as high contents of proline and carotenoids. While Heterochlamydomonas sp. exhibited higher levels of catalase and protein, Chlorococcum sp. produced greater amounts of malondialdehyde, a measure of lipid peroxidation, in the presence of PNP. Chlorella sp. tolerated PNP by producing large quantities of antioxidants coupled with less lipid peroxidation, while Chlorococcum sp. was susceptible, as evidenced by low antioxidant production and high lipid peroxidation. During 7-d exposure, Chlorella sp., Heterochlamydomonas sp., and Chlorococcum sp. were able to remove 39, 18, and 4% of 20 mg L(-1) PNP, respectively. The present results indicate that proline, carotenoids and malondialdehyde are the potential biomarkers for assessing PNP toxicity toward microalgae, and their response could be considered for differentiating tolerant and susceptible strains. Moreover, there is a clear correlation between PNP removal and antioxidant synthesis in microalgae on exposure to the pollutant.

Treatment of p‐nitrophenol in an adsorbent‐supplemented sequencing batch reactor

The objective of this research was to evaluate the treatment of p‐nitrophenol (PNP) as a sole organic carbon source using a sequencing batch reactor (SBR) with the addition of adsorbent. Two types of adsorbents, namely powdered activated carbon (PAC) and pyrolysed rice husk (PRH) were used in this study. Two identical SBRs, each with a working volume of 10 L, were operated with fill, react, settle, draw and idle periods in the ratio of 2:8:1:0.75:0.25 for a cycle time of 12 h. The results showed that, without the addition of adsorbent, increasing the influent PNP concentration to 200 mg/L resulted in the deterioration of chemical oxygen demand (COD) removal efficiency and PNP removal efficiency in the SBRs. Improvement in the performance of the SBR was observed with the addition of PAC. When the dosage of 1.0 g PAC/cycle was applied, COD removal of 95% and almost complete removal of PNP were achieved at the influent PNP concentration of 300 mg/L. The kinetic study showed that the rates of COD and PNP removal can be described by the first‐order kinetics. The enhancement of performance in the PAC‐supplemented SBR was postulated to be due to the initial adsorption of PNP by the freshly added and the bioregenerated PAC, thus reducing the inhibition on the microorganisms. The PRH was found to be ineffective because of its relatively low adsorption capacity for PNP, compared with that of PAC.

Statistical medium optimization and biodegradative capacity of Ralstonia eutropha toward p-nitrophenol

The effect of p-nitrophenol (PNP) concentration with or without glucose and yeast extract on the growth and biodegradative capacity of Ralstonia eutropha was examined. The chemical constituents of the culture medium were modeled using a response surface methodology. The experiments were performed according to the central composite design arrangement considering PNP, glucose and yeast extract as the selected variables whose influences on the degradation was evaluated (shaking in reciprocal mode, temperature of 30 degrees C, pH 7 and test time of about 9 h). Quadratic polynomial regression equations were used to quantitatively explain variations between and within the models (responses: the biodegradation capacity and the biomass formation). The coefficient of determination was high (R(adjusted)(2) = 0.9783), indicating the constructed polynomial model for PNP biodegradative capacity explains the variation between the regressors fairly well. A PNP removal efficiency of 74.5% occurred within 9 h (15 mg/L as the initial concentration of PNP with use of yeast extract at 0.5 g/L).

Preparation and sorption studies of β‐cyclodextrin/epichlorohydrin copolymers

Abstractβ‐Cyclodextrin (β‐CD) copolymer materials were synthesized by reacting different mole ratios (1 : 15, 1 : 25 and 1 : 35) of β‐CD with epichlorohydrin (EP). The products were characterized using N2 porosimetry, Fourier Transform Infrared spectroscopy, 13C CP‐MAS NMR spectroscopy, thermogravimetry analysis, elemental (C and H) analysis, and scanning electron microscopy. The sorption properties in aqueous solution were studied using p‐nitrophenol (PNP) with UV–Vis spectrophotometry. Sorption isotherms were obtained at pH 4.6 and three temperatures (22, 35, and 45°C) and at pH 10.3 at 22°C. The isotherms were analyzed using the BET isotherm model and the sorption parameters provided estimates of the surface area, sorption capacity, and isosteric heats of sorption for each polymeric material. The estimated surface areas are as follows: 58.2, 52.1, and 90.1 m2/g at pH 4.6. At pH 10.3, the estimated surface areas are 44.2, 40.5, and 58.5 m2/g, respectively. The removal efficiency of PNP by the polymeric materials ranged between 4.5 and 58% for the conditions investigated whereas the isosteric heats ranged between −24.5 and −13.6 kJ/mol. Removal efficiencies were concluded to strongly depend on the sorption conditions such as pH, temperature, and the relative amounts of sorbent and dye in aqueous solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Characterization of insolubilized humic acid and its sorption behaviors

Insolubilized humic acid (IHA) was prepared in the laboratory by heating approach. Through the comparison between the endothermic peaks, optimal heating temperature was determined to be 330°C. The modified IHA then was characterized by TG-DTA, SEM, FTIR, element analysis, and nitrogen adsorption–desorption isotherms. The removal efficiency of p-nitrophenol from the aqueous solution by adsorption onto solid IHA surfaces was shown to be a function of pH, reaction temperature, and p-nitrophenol concentration. Adsorption equilibrium data satisfactorily fitted the Langmuir adsorption isotherm. Under a certain concentration range, the removal rate of p-nitrophenol at pH 3.5 could reach 24, 29, and 35 mg/g at a temperature of 25, 35, and 45±0.1°C. The results suggest that IHA could play a role as a potential efficient absorbent to remove organic contaminants, e.g., utilized to purify water contaminated by organic compounds.

Performance of anaerobic baffled reactor (ABR) treating synthetic wastewater containing p-nitrophenol

In this study, the effect of increasing p-nitrophenol (PNP) concentrations on the performance of anaerobic baffled reactor (ABR) (chemical oxygen demand (COD), removals, volatile fatty acid (VFA), p-aminophenol (PAP) and methane gas productions) was investigated through 240 days. The PNP concentrations were raised to 700 from 10 mg/L corresponding to PNP loading rates of 0.97 and 67.9 g/m 3 day. The PNP and COD removal efficiencies were 99 and 90% at PNP loading rates as high as 33.9 g/m 3 day, respectively, through the acclimation of anaerobic granular sludge. After this loading rate, the removal efficiencies decreased to 79%. The COD removal efficiencies were high in compartment 1 ( E = 78–93%) while a small amount of COD removal was achieved in compartments 2 and 3. The PNP removal efficiencies were approximately 90% in all PNP loading rates except for loading rate of 0.97 g/m 3 day. The maximum PNP removal efficiency was measured as 99% at a loading rate of 8.32 g/m 3 day. The optimum PNP loading rate for maximum COD, PNP removals and methane yield was 8.32 g/m 3 day. The total, methane gas productions and methane percentages were approximately 2160–2400 mL/day and 950–1250 mL/day and 44–52% for the PNP loading rates varying between 4.36 and 33.9 g/m 3 day, respectively. For PNP loading rates varying between 33.9 and 67.9 g/m 3 day, the total, methane gas productions and methane percentages were approximately 2160 and 960 mL/day and 44%, respectively. The highest total volatile fatty acid (TVFA) concentrations were found in the first compartment with fluctuated values varied between 50 and 200 mg/L indicating the acidogenesis. p-Aminophenol was found as the main intermediate through anaerobic degradation of PNP which later was broken down to phenol and ammonia.