Effect Of Pollutant Concentration Research Articles

Deciphering the Pivotal Reaction Conditions for Hydrogen Production from Tar Catalytic Cracking by Perovskite

The catalytic cracking of pyrolysis gasification tar into H2 has garnered significant attention due to its exceptional conversion efficiency. In this study, the effects of pollutant concentration, residence time, weight hourly space velocity (WHSV), and reaction temperature on the hydrogen performance of LaFe0.5Ni0.5O3 perovskite were comprehensively investigated. Results revealed that moderate pollutant concentration (0.3 g/L), low-medium residence time (250 SCCM), and low WHSV (0.24 gtoluene/(gcat·h)) facilitated efficient interaction between LaFe0.5Ni0.5O3 and toluene, thus achieving high hydrogen production. An increase in reaction temperature had minimal effect on the hourly hydrogen production above 700 °C but caused a significant increase in methane production. Additionally, the effects of oxygen evolution reactions, methane reactions, and methane catalytic cracking reactions of perovskite induced by different reaction conditions on tar cracking products were discussed in detail. Compared to previous reports, the biggest advantages of this system were that the hydrogen production per gram of tar was as high as 1.002 L/g, and the highest hydrogen content in gas-phase products reached 93.5%, which can maintain for approximately 6 h. Finally, LaFe0.5Ni0.5O3 showed good thermal stability, long-term stability, and catalyst reactivation potential.

Ozonolysis of ketoprofen in polluted water: Reaction pathways, kinetics, removal efficiency, and health effects

Ketoprofen (KET), as a non-steroidal anti-inflammatory drug frequently detected in aqueous environments, is a threat to human health due to its accumulation and low biodegradability, which requires the transformation and degradation of KET in aqueous environments. In this paper, the reaction process of ozone-initiated KET degradation in water was investigated using density functional theory (DFT) method at the M06-2X/6-311++g(3df,2p)//M06-2X/6-31+g(d,p) level. The detailed reaction path of KET ozonation is proposed. The thermodynamic results show that ozone-initiated KET degradation is feasible. Under ultraviolet irradiation, the reaction of ozone with water can also produce OH radicals (HO·) that can react with KET. The degradation reaction of KET caused by HO· was further studied. The kinetic calculation illustrates that the reaction rate (1.99 × 10−1 (mol/L)−1 sec−1) of KET ozonation is relatively slow, but the reaction rate of HO· reaction is relatively high, which can further improve the degradation efficiency. On this basis, the effects of pollutant concentration, ozone concentration, natural organic matter, and pH value on degradation efficiency under UV/O3 process were analyzed. The ozonolysis reaction of KET is not sensitive to pH and is basically unaffected. Finally, the toxicity prediction of oxidation compounds produced by degradation reaction indicates that most of the degradation products are harmless, and a few products containing benzene rings are still toxic and have to be concerned. This study serves as a theoretical basis for analyzing the migration and transformation process of anti-inflammatory compounds in the water environment.

Ag/rGO/Bi2WO6 nanocomposite as a highly efficient and stable photocatalyst for Rhodamine B degradation under visible light irradiation

An efficient Ag/rGO/Bi2WO6 nanocomposite was synthesized by the precipitation-photoreduction method. The resulting Ag/rGO/Bi2WO6 showed excellent photocatalytic activity for the photodegradation of Rhodamine B (RhB), with 15%Ag/rGO/Bi2WO6 photodegrading 96.97% of RhB in 180 min, which was 1.28, 1.09 and 1.05 times higher than that of Bi2WO6, Ag/rGO, and rGO/Bi2WO6, respectively. The effect of noble metal Ag's surface plasmon resonance and Schottky barrier, as well as the superior electron transfer ability of rGO, dramatically improved photo-generated electron-hole pair separation and transfer efficiency. In addition, the effects of pollutant concentration, pH, and catalyst dosage on Ag/rGO/Bi2WO6 photocatalytic performance also were explored. Furthermore, the free-radical trapping tests revealed that the primary active radicals in the catalytic system are hole (h+), superoxide radical (•O2−), and hydroxy radical (•OH). Additionally, after four recycling, the photocatalytic performance of the Ag/rGO/Bi2WO6 composite did not show a significant decline. As a result of this research, the Ag/rGO/Bi2WO6 catalyst, as developed, has a bright potential for environmental purifying.

Visible light-driven photoactive L-Methionine (CNS tripledoped)-TiO2/ZnO nanocomposite aiming for highly efficient photodegradation of xenobiotic compounds in wastewater

Inspired by the most promising green technology for xenobiotics degradation, this work proposes novel visible-light-responsive L-Methionine (CNS tripledoped)-TiO2/ZnO photocatalysts successfully synthesized by sol-gel technique with various loadings of L-Methionine and different mass ratios of TiO2/ZnO. Subsequently, their application for photodegradation of direct red 16 (DR16) and biologically treated palm oil mill effluent (POME) were investigated. The prepared nanocomposites were thoroughly characterized to assess their morphological, optical, and structural properties. The effects of pollutant concentration, photocatalyst loading, irradiation time, and initial pH on the photodegradation process of DR16 and biologically treated POME were investigated using response surface methodology (RSM). The obtained RSM results showed that DR16 was completely removed at pH of 4, 15 mg/L of DR16, and 1 g/L of photocatalyst after 60 min. The complete degradation of biologically treated POME was obtained at original pH, 300 mg/L of COD concentration, 2 g/L of photocatalyst, and irradiation time of 3 h.

A Simple g-C3N4/TNTs Heterojunction for Improving the Photoelectrocatalytic Degradation of Methyl Orange

In this work, highly ordered titanium dioxide nanotube arrays (TNTs) were first prepared by anodic oxidation method. Then, g-C3N4/TNTs heterojunctions were prepared by ultrasonically loading graphitic carbon nitride (g-C3N4) onto the TNTs. The morphology and crystal structure of TNTs and g-C3N4/TNTs were characterized by SEM/TEM and XRD. The photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TNTs and g-C3N4/TNTs was studied in a PEC degradation system. The photocatalytic (PC), electrocatalytic (EC), and PEC degradation properties were compared, and the effect of pollutant concentration on the degradation performance of the catalysts was analyzed. According to the experimental results, the degradation rate of MO with TNTs only reaches 65.1% after 120 min, while the degradation rate of MO with g-C3N4/TNTs reaches 84.6% in the same time. Due to the synergistic effect of light and electricity, the PEC degradation efficiency of the two catalysts is greater than the sum of PC and EC degradation, proving that g-C3N4/TNTs heterojunctions provide excellent PEC performance for the degradation of MO.

Removal of an emerging pharmaceutical pollutant, sulfasalazine, by adsorption onto pomegranate peels

The removal of an emerging pharmaceutical pollutant, sulfasalazine, which frequently detected in pharmaceutical industry wastewater as well as in drinking water, has been investigated by adsorption on a biosorbent, prepared from pomegranate peels in order to valorize food processing waste. After characterizing and determining the surface functions, morphology and textural properties of the biosorbent pomegranate peels, the effect of pollutant concentration, pH and adsorbent amount on the adsorption activity were evaluated by varying one parameter at a time. Results showed a quasi-total removal of sulfasalazine for a pH higher than 4.8, an initial pollutant concentration of 50 mg L−1 and an adsorbent mass of 0.5 g. The isotherm, kinetic and thermodynamic parameters for sulfasalazine adsorption on the biosorbent have been estimated. Results revealed that the adsorption of sulfasalazine on pomegranate peels is a homogenous monolayer, spontaneous and endothermic process following a pseudo-second-order kinetic.

The effect of air pollution on drivers' safety performance.

Numerous studies have determined the adverse effects of air pollution on the health, welfare, and comfort of humans. More recently, the effects of air pollution on cognitive performance of humans are also focused. However, as a group in direct exposure to air pollution, drivers are rarely studied. The present study aims to evaluate the effect of air pollution on the performance of drivers. Their performance is evaluated by observing the number of recorded accidents. The effect of pollutant concentration (primarily PM2.5) on the number of accidents is investigated in a case study in Tehran. The temperature inversion phenomenon is used as an instrumental variable in a two-stage least squares method. The results indicate that temperature inversion had a significant positive correlation with the concentration of pollutants. Considering temperature inversion as an instrumental variable for these pollutants, it is observed that 1 μg/m3 increase in concentration of PM2.5, increased the number of accidents approximately by 4% in 1 day, for the range of parameters studied. No significant relationship was observed regarding the effect of NO2 and CO on accidents during the study period.

Application of Density Functional Theory computation (DFT) and Process Capability Study for performance evaluation of Orthophosphate removal process using Polyaniline@Hematite-titaniferous sand composite (PANI@HTS) as a substrate

A new approach is adopted in this study to eliminate orthophosphates in the aqueous medium. It is about synthesizing a composite from a conductive polymer (Polyaniline) and a sandy material (Hematite-titaniferous sand). The synthesized composite (PANI@HTS) and its components were characterized with (XRD) X-ray diffraction, (XRF) X-ray fluorescence, (SEM) scanning electron microscopy coupled with (EDS) energy dispersive X-ray spectroscopy, (FTIR) Fourier-transform infrared spectroscopy and laser diffraction particle size analysis. The phenomenon of adsorption of orthophosphates on PANI@HTS has found to be dependent on several factors, such as adsorbent dose, pH, contact time and pollutant concentration. From the study of adsorption kinetics and the effect of pollutant concentration, the Langmuir model and the pseudo second order model were the most suited for explaining adsorption phenomena with a highest correlation (R2 > 0.98). The adsorbed amount that was found in this study reaches 16.15 mg/g. The adsorption mechanism of orthophosphate ions onto PANI@HTS composite was computationally investigated using Density Functional Theory (DFT). The adsorbate-adsorbent interfacial interactions are assumed to be physisorption in nature due to the low values of binding energy and electronic charge transfer. This DFT simulation result is in good adequacy with the experiment. The capability study of the present process has shown that our method is capable, satisfactory and can be applied on a large scale.

Deep eutectic solvent as an efficient modifier of low-cost adsorbent for the removal of pharmaceuticals and dye

Waste from biomass was used to prepare a low–cost biochar–clay hybrid adsorbent. The hybrid adsorbent was synthesised by combining Kaolin with biomass (Vitex doniana), thereafter, modified with Deep Eutectic Solvent (DES). The materials were characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FTIR), Thermal gravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET), also, pHpzc of the materials were studied. The resultant adsorbents were used for both column and batch adsorption of organic pollutants; dye (Acid Blue 74; AB74) and pharmaceuticals (ciprofloxacin; CIP and acetaminophen; ACTE). Column adsorption capacity, effect of pollutant concentration and effect of flow rate were studied, also, the column was modelled using Thomas, Yoon-Nelson and Adams-Bohart model. Furthermore, batch adsorption experiments were performed, effect of change in pH, time, dose and concentration were studied. Batch adsorption data were fitted with isotherm and kinetic models. The experiment showed tremendous increase in adsorption capacity when the hybrid adsorbent (HYD) was modified with DES (HYD–DES). Acid Blue 74 on HYD–DES has the highest column sorption capacity followed by ciprofloxacin and acetaminophen. Adsorption was favoured at pH range of 2–10 for both AB74 and ACTE as there is no significant changes in the % removal performance, while adsorption was best at pH 6 and above for CIP. AB74 and CIP are best described by Langmuir isotherm, whereas ACTE adsorption was best explained by Freundlich isotherm equilibrium. The DES modified HYD has shown it can be effectively utilised as possible adsorbent for adsorbing organic dyes and pharmaceuticals.

Heterogeneous Sono-Fenton treatment of decabromodiphenyl ether (BDE-209): Debromination mechanism and transformation pathways

Polybrominated diphenyl ethers, used as flame retardants are a cause of concern over past several years, due to their toxicity, bioaccumulation and widespread distribution. In this work, the combination of ultrasound and advanced Fenton process was investigated for the degradation of Decabromodiphenyl ether (BDE-209). The effect of pollutant concentration, solution pH, ultrasonic power density and loading of Fenton’s reagent on the extent of BDE-209 degradation were studied. The results indicated an enhancement in the degradation of BDE-209 during Sono-Fenton treatment, leading to a complete degradation within 80 min of treatment, whereas only 40% and 25% degradation were achieved during ultrasound and Fenton treatment alone. To understand the degradation mechanism, analytical techniques including High performance liquid chromatography and Gas chromatography mass spectroscopy were employed to monitor the concentrations of parent compound along with degradation products. The degradation mechanism was proposed based on the identified degradation products. Total organic carbon (TOC) analysis demonstrated 60% TOC removal within 80 min of treatment. The obtained results suggest that the initiation of BDE-209 degradation during Sono-Fenton treatment followed thermal decomposition at bubble-vapor interface along with reductive debromination at iron surface, accompanied by oxidative degradation of lower brominated congeners at liquid bulk. This work illustrated an effective method for the removal of BDE-209 and hence providing an efficient wastewater treatment solution for recalcitrant pollutants.

Effect of Pollutant Concentration During Isolation on the CH4 Biodegradation Kinetics, Population Structure and PHB Accumulation

Effect of Pollutant Concentration During Isolation on the CH₄ Biodegradation Kinetics, Population Structure and PHB Accumulation

Effect of pollutant concentrations on growth characteristics of macrophytes in a constructed wetland treating municipal combined sewage

Abstract Constructed wetlands (CWs) have been used for contaminated water treatment for more than three decades. However, the ecological effects of the pollutant loading on CWs are not well known. In this study, five wetland plants (Phragmites karka (PK), Typha orientalis Presl (TO), Cyperus malaccensis Lam (CM), Schoenoplectus mucronatus (SM), Hygrophila pogonocalyx Hayata (HP)) were chosen and three study sites (42 × 42 cm) were used in a CW in Taiwan. The bioaccumulation of vegetation and effects on wetland ecosystem were tested with different pollutant concentrations of municipal combined sewage. The mean concentrations of BOD5, NH4-N, and total phosphorus (TP) at the three study sites were 12.1 ≈ 44.3 mg l−1, 3.6 ≈ 19.8 mg l−1, and 0.4 ≈ 1.9 mg l−1, respectively. The results show that higher nutrient concentrations led to higher bioaccumulations of wetland plants, and the amount of biomass are significantly different in each species. The highest growth rate is observed in CM, in 5314 g-biomass (dry weight) m−2. The drying ratio (wet weight/dry weight) increases with the growth of all five species. The conclusion is that the input of nutrients within the polluted water will increase the production of wetland plants, but may possibly decrease the biodiversity due to higher competition around different species at the same time.

Surfactant removal from water solutions by means of ultrafiltration and ion-exchange

The aim of the study was to compare the removal efficiency of anionic surfactant (belonging to alkylbenzenesulfonate family) from water solutions by means of ultrafiltration and ion-exchange. During the first stage of the experiments, the influence of surfactant type and its concentration, membrane cut-off and polymer material on ultrafiltration performance was evaluated. The next stage of the study was focused on effectiveness of ion-exchange using MIEX resin as a method of surfactant removal from water solutions. The effect of pollutant concentration, resin dose, mixing time, pH of the solution and mineral salt presence was assessed. It was noticed that the ultrafiltration separation of surfactant was significantly influenced by membrane material. The best separation characteristics were achieved by polysulfone and polyethersulfone membranes. The PES5 and PS5 ones allowed lower the surfactant concentration to be achieved ranging from 71 to 91% and from 55 to 81% for 5 kDa and 10 kDa. High surfactant retention was obtained at lower concentrations. With the increase in surfactant concentration the retention values decreased with a slight increase in CMC value. From the experimental investigation, the magnetic ion-exchange resin was found to be very effective in anionic surfactant removal in a wide range of concentrations. As well as the ion-exchange process was shown to be insensitive to the pH value of the solution and the mineral salt presence.

Sorption properties toward substituted phenolic derivatives in water using macroporous polyamines containing ?-cyclodextrin

Macroporous polyamines containing β-cyclodextrin (β-CD) are used for the recovery of various organic pollutants from aqueous solutions. Several insoluble polyamines with various degrees of β-CD were prepared. Studies concerning the sorption kinetics, the effect of pollutant concentration, pH of the solutions, and β-CD content are presented here. The results of sorption experiments show that these sorbents exhibit high sorption capacities toward substituted phenolic derivatives. The mechanism of sorption is both physical adsorption in the resin polymer network through acid–base interactions, ion exchange, and hydrogen bonding due to the amino groups and the formation of an inclusion complex due to the β-CD molecules through host–guest interactions, and hydrophobic interactions such as guest–guest interactions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2903–2910, 1999

Sorption properties toward substituted phenolic derivatives in water using macroporous polyamines containing β‐cyclodextrin

Macroporous polyamines containing β-cyclodextrin (β-CD) are used for the recovery of various organic pollutants from aqueous solutions. Several insoluble polyamines with various degrees of β-CD were prepared. Studies concerning the sorption kinetics, the effect of pollutant concentration, pH of the solutions, and β-CD content are presented here. The results of sorption experiments show that these sorbents exhibit high sorption capacities toward substituted phenolic derivatives. The mechanism of sorption is both physical adsorption in the resin polymer network through acid–base interactions, ion exchange, and hydrogen bonding due to the amino groups and the formation of an inclusion complex due to the β-CD molecules through host–guest interactions, and hydrophobic interactions such as guest–guest interactions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2903–2910, 1999

Uranium migration through intact sandstone: effect of pollutant concentration and the reversibility of uptake : R. Sims, T. A. Lawless, J. L. Alexander, D. G. Bennett & D. Read, Journal of Contaminant Hydrology, 21(1–4), 1996, pp 215–228

Uranium migration through intact sandstone: effect of pollutant concentration and the reversibility of uptake : R. Sims, T. A. Lawless, J. L. Alexander, D. G. Bennett & D. Read, Journal of Contaminant Hydrology, 21(1–4), 1996, pp 215–228

Uranium migration through intact sandstone: effect of pollutant concentration and the reversibility of uptake

A series of core flood experiments has been performed to investigate the migration behaviour of uranium under rigidly controlled conditions. Intact sandstone cores, pre-equilibrated with synthetic groundwater, were flooded with uranium solutions at varying concentrations and the transport process monitored as a function of pH, tracer concentration and the concentration of a competing ion, cadmium. In each case a substantial amount of uranium was retained by the core, implying a strong interaction with the rock matrix. The adsorption process was found to be highly concentration dependent; however, such that the finite retention capacity of an intact core can be exhausted within a relatively short time. The reversibility of uptake was studied by attempting to displace adsorbed uranium by injected cadmium and flushing with brine. Most of the uranium was readily recoverable but a small percentage is released very slowly on flushing, suggesting conversion to a more stable form. Prior to performing each experiment a simulation was carried out using a one-dimensional coupled chemical transport code, encompassing a thermodynamic description of the electrical double layer. The model was successful in predicting a priori the dominant trends in the uranium migration behaviour which may aid in model developments for more complex geochemical regimes than those studied here.