Pollutants In Industrial Effluents Research Articles

Synergistic reduction of nitrophenols by Au-CDs nanoconjugates with NaBH4

Developing sustainable and innovative approaches for the efficient reduction of nitrophenols is crucial for environmental remediation, for managing health concerns posed by their widespread presence as hazardous pollutants in industrial effluents and contaminated water. We report the use of 12.9 ± 1 nm (TEM data) sized gold carbon dot nanoconjugates (Au@CDs) for catalytic conversion of o, m, p-nitrophenols to aminophenols by sodium borohydride. A simple approach was followed to synthesize ultra-small and highly stable Au@CDs, using citric acid and PEG as reducing and stabilizing agents. X-ray diffraction analysis verified the formation of nano-crystalline nanoconjugates. These nanoconjugates showed a remarkable catalytic activity in the range of 0.22–0.33 s−1 (varying with nanoconjugate concentration) which was much higher compared to conventional chemical methods of reduction. All the catalytic reaction experiments were performed at room temperature (27 ± 2 °C). Furthermore, an increase in rate constant was observed with increasing concentration of nanoconjugates. The catalytic activity of Au@CDs nanoconjugates was observed to be in order of m-nitrophenol > o-nitrophenol > p-nitrophenol with apparent rate constant (k aap) values of 0.068, 0.043 and 0.031, respectively. Comparative analysis with GNPs, CDs and Au@CDs nanoconjugates stated that the nanoconjugates had superior catalytic activity. The research can have significant implications in the development of new strategies for environmental remediation and biomedical applications.

Sonocatalytic degradation of nitrobenzene with metal oxide clay nanocomposites

AbstractBACKGROUNDThe presence of a wide range of persistent toxic organic pollutants in industrial effluents poses a serious threat to human and environmental health, emphasising the necessity for developing cost‐effective methods for treating toxic effluents. This study focuses on the synthesis, characterization and evaluation of metal oxide [iron (Fe), copper (Cu) and zinc (Zn)]‐doped clay composite for the sonocatalytic degradation of nitrobenzene (NB) in the presence of ultrasound.RESULTS AND CONCLUSIONSAmong the metal oxides studied, Cu and Fe oxide‐modified clay performed better in the degradation of NB (~99% in the presence of air) compared to a ZnO/clay composite. Process optimization studies were carried with CuO/clay composite at different pHs (2.5–11.5), feed concentrations (50–200 mg L−1) and catalyst loadings (0.25–1.0 g L−1). Neutral pH conditions and higher catalyst loadings of 1 g L−1 were found to be optimal for the efficient degradation of 50 ppm NB. Among the scavengers tested, ethylenediamine tetra acetic acid exhibited strong scavenging effects, resulting in reduced NB degradation compared to isopropyl alcohol and tin tetrachloride, regardless of the scavenger concentration (0.5 and 40 mmol L−1). The catalyst was found to be sufficiently stable for up to four cycles under identical conditions. Additionally, these materials were found to be effective in the degradation of other pollutants [Terephthalic acid, Rhodamine‐B, Ciprofloxacin]. These findings contribute to the development of cost‐effective strategies for the treatment of industrial effluents, reducing the risks posed to both the environment and human health. © 2023 Society of Chemical Industry (SCI).

Synthesis of Binary Metal Doped CuO Nanoarchitecture for Congo red dye Removal: Synergistic Effects of Adsorption and Mineralization Techniques

Herein, a microwave-assisted fabrication technique has been practiced for the generation of pristine CuO and Cd/Zn co-doped CuO (Cu0.94Cd0.03Zn0.03O) nanopowders with the identical weight ratio of cadmium and zinc metals. The structure, chemical nature, shape, and optical response of CuO and Cu0.94Cd0.03Zn0.03O were assessed by PXRD, FESEM, FTIR, and UV–vis analytical techniques. PXRD results affirmed that CuO and Cu0.94Cd0.03Zn0.03O have developed in a single monoclinic phase; other extra phases are absent. The crystallite sizes of CuO and Cu0.94Cd0.03Zn0.03O were identified as 18.5 nm and 14.39 nm. The FESEM image of the Cu0.94Cd0.03Zn0.03O sample demonstrated a nanosheet-like morphology that was developed after the co-doping of Zn and Cd metal ions. FTIR graphs established the occurrence of Cu–O main bonds in both fabricated nanopowders. The UV–vis examination demonstrated that Cd and Zn co-doping has substantially reduced the energy gap of pristine CuO from 2.0 eV to 1.54 eV. This massive reduction in CuO bandgap assists it in catching extra photons to stimulate valence-band electrons and hence boosts the activity of the catalyst under sunlight irradiations. Moreover, including Cd and Zn has also effectively hindered the e−/h+ recombination in CuO throughout the photocatalysis process. The photocatalytic activities of pristine CuO and Cu0.94Cd0.03Zn0.03O nanosheets were probed against Congo-red (CR) pollutants under sunlight irradiations. The mineralization efficiency was detected as maximum (∼87.88%) for Cu0.94Cd0.03Zn0.03O nanosheets in contrast to pristine CuO nanostructures. Cu0.94Cd0.03Zn0.03O nanosheets, due to their astonishing properties, could be an economical alternative in creating intelligent strategies for mineralizing organic pollutants in industrial effluents.

English

This study was conducted to investigate the effects of spent engine oil and industrial effluent on the soil and Dioscorea bulbifera plant. Spent engine oil (SEO) was added to the buckets filled with 15 kg of loamy soil at different volumes of 0 , 75 , 225, and 375mL. Another bucket was filled with 15 kg of industrial effluent (IE). The results showed that SEO in soil has highly significant (p ≤ 0.05) effects on some of the soil's physicochemical properties. Industrial effluent (IE) had the highest nitrogen content (0.89%) while the lowest was in 75 mL15kg-1 (0.72%). pH was higher in control (4.29) and the lowest was at 375 mL15kg-1 (4.89). The chlorophyll content range was 274.06 mg g-1 (IE) – 349.60 mg g-1 (control). Also, bulbils from IE had the least fresh and dry weight (20.21 g and 14.73 g, respectively). The bioaccumulation factor (BAF) of all heavy metals examined was less than 1, except for copper. Heavy metal uptake order by the bulbil is Cu > Fe > Zn > Pb. Considering the detrimental effects of SEO and IE pollution on soil and plants, it has become necessary for the government to have a policy that will prevent indiscriminate disposal of waste.

Fabrication of Z-scheme Bi7O9I3/g-C3N4 heterojunction modified by carbon quantum dots for synchronous photocatalytic removal of Cr (Ⅵ) and organic pollutants

Chromium(VI) (Cr(VI)), a highly toxic metal ion, generally co-exists with organic pollutants in industrial effluents. The clean and effective technology for water purification is an imperative issue but still a challenging task. A series of Bi7O9I3/g-C3N4 (BOI/CN) composites modified by lignin-derived carbon quantum dots (CQDs) were fabricated by hydrothermal method and applied for synchronous photocatalytic removal of Cr (Ⅵ) and levofloxacin (LEV). With the modification of CQDs in BOI/CN heterojunction, the 0.5-CQD/BOI/CN photocatalyst (0.5% content of CQDs) exhibited stronger light-harvesting capacity, more efficient charge separation, and faster electron transfer. Compared to those of BOI (51.2%), CN (36.8%), and BOI/CN (74.4%), the photoreduction efficiency of Cr(VI) reached up to 100% by 0.5-CQD/BOI/CN under 60 min of light irradiation, together with 94.8% degradation efficiency of LEV. The degradation of LEV was dominantly controlled by active species (•OH and •O2−) identified by electron paramagnetic resonance analysis and free radical trapping experiments. The intermediates of LEV were determined by LC-MS and the possible degradation pathway was speculated in combination with density functional theory calculation, involving defluorination, decarboxylation, quinolone rings opening, and piperazine moieties oxidation reactions. This work provides an advanced strategy for the fabrication of high-efficiency CQDs-based Z-scheme photocatalysts for environmental remediation.

Performance Studies of TiO<sub>2 </sub>Catalyst for Phenol Degradation

Water is a valuable source that directly impact human life. The expansions of globalization as well industrialization led to water pollution, thus became worsen over the time. The issue of degradation of organic and inorganic pollutants become very serious from ecological point of view, especially organic pollutants in industrial effluents due to difficult to be remove by means of conventional technologies. Phenol compound in wastewater effluents can threatens the human and public health, water supplies, and has negative impacts on the ecosystems. In addition, the TiO2 semiconductor metal oxide provides a great interest among researchers to overcome this problem via photocatalytic reaction under advanced oxidation processes (AOPs). The AOPs mainly used the hydroxyl radicals to attack and destroy a wide range of harmful dyes into non-toxic products, CO2 and water at ambient temperature. Therefore, in this study, the synthesized TiO2 catalyst gave the remarkable degradation of phenol up to 96.3%, meanwhile the commercial TiO2 only show 80.3%, in respectively under similar optimum conditions of 10 mg/L at pH 5 with dosage of 1.25 g/L within 90 mins time reaction under light irradiation.

Fruit waste-derived cellulose and graphene-based aerogels: Plausible adsorption pathways for fast and efficient removal of organic dyes

A wide range of organic pollutants in industrial effluents, agricultural runoff, and domestic discharges are exacerbating water scarcity, leading to water-borne ailments, and adversely affecting the marine ecosystem and biodiversity. The efficient, sustainable, and cost-effective materials need to be addressed urgently for the removal of organic pollutants. Herein, ultra-light (0.018 g.cm−3) and highly porous (96.4%) composite aerogel is prepared by gelatinization of graphene oxide with fruit waste-derived cellulose. The macroscopic porosity generated by interconnecting cellulosic skeleton and graphene oxide sheets via hydrogen bonding network provided ample avenues for transport and diffusion of organic dyes-enriched wastewater throughout the cellulose-graphene oxide composite aerogel (CGA). Consequently, organic dyes are efficiently adsorbed by easily accessible surface sites distributed throughout the CGA. The size, charge, and chemical structure of organic dyes along with textural features and accessible surface active sites of CGA governed the adsorption process. The spectroscopic analyses based on FTIR, Raman, and XPS measurements suggest electrostatic, n-π, π-π, cation-π interactions, dipole–dipole hydrogen, and Yoshida hydrogen linkages as major interactive pathways for the adsorption of organic dyes by the CGA. Moreover, the composite aerogel furnished an excellent recyclability for the adsorptive removal of organic pollutants from wastewater. The present work promises the potential of 2D nanostructured layered materials and fruit-waste-derived composite aerogels for sustainable utilization in wastewater treatment, which can be an excellent step towards water security.

Removal of methylene blue from textile waste water using kaolin and zeolite-x synthesized from Ethiopian kaolin.

The wastewater generated from textile factories is linked to one of the main water pollution problems; therefore, it is important to reduce the pollutants in industrial effluents before their discharge into environment. The present study was to investigate the appropriateness zeolite-x and kaolin as effective adsorbents for removal of methylene blue from the textile wastewater. Batch adsorption experiments were carried out to assess parameters that influence the adsorption process. The prepared zeolite-x and kaolin were characterized by Fourier Transform Infrared and X-ray diffraction techniques. The results of this study showed that the particle size is 40.77 nm and 0.45 nm kaolin and zeolite-x respectively. The performance of zeolite-x adsorbent is best at the optimum pH 4 with removal efficiency of 97.77% and kaolin adsorbent at pH 6 with removal efficiency of 86.86%. The optimum contact time was obtained at 60 and 80 minutes for zeolite–x and kaolin respectively. While optimum adsorbent dosage was obtained at 0.4 and 0.6 grams with removal efficiency of 97.12% and 87.75% for the zeolite-x and kaolin adsorption experiment respectively. The confirmed square sum errors values are 1.0×10−4 and 1.0×10−3 for zeolite-x and kaolin, respectively. The Adsorption isotherms results have well fitted to Freundlich isotherm than Langmuir isotherm. The adsorption kinetics results were best fitted the pseudo second order model. The result shows that the zeolite-x has high removal efficiency than kaolin at the same operating conditions. Application of this method can be economically, environmentally, and socially feasible to address wastewater problems. Further research has to be carried out on the removal capacity of this adsorbent for organic dyes not only from the textile industry but also from leather industries and soap industries.

The First Application of Moroccan Perlite as Industrial Dyes Removal

A local perlite mineral (P1) was used to remove the industrial dyes Remazole Brilliant 19 (RB19) and Drimarene Yellow (YD) from an aqueous solution. Prior to any investigation, P1 was characterized using powder X-ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy, X-ray fluorescence, Brunauer-Emmett-Teller analysis, and electrophoretic mobility in order to establish the adsorption behavior-properties relationship. We used a sequential methodology of factorial design of experiments (DOE) and response surface methodology (RSM) to evaluate experimental variables that influence the adsorption process. Under optimal conditions, removals of RB19 and YD were achieved at respectively 95% and 88%. The validity of the process was justified by the values of three statistical indicators: Fisher’s high value (F = 58.79 for RB19, F = 34.82 for YD), the probability P (P ≤ 0.001 for DY and RB19) and the coefficient of determination R2 (0.9674 for YD and 0.9821 for RB19). The mass transfer of RB19 and YD at the solution/adsorbent interface was described using a pseudo-second-order rate law. The adsorption process for RB19 was endothermic, while it is exothermic for YD. The phyto-toxicity was also investigated to evaluate the toxicity level of YD and RB19 before and after sorption on P1 material. Overall P1 is very attractive as an efficient, low-cost and eco-friendly sorbent for the remediation of hazardous organic pollutants in industrial effluents.

Ultrasound‐assisted synthesis of FeTiO3/GO nanocomposite for photocatalytic degradation of phenol under visible light irradiation

Phenolic compounds are dangerous pollutants in industrial effluents that have caused many human and environmental problems. These compounds are resistant to decomposition conventional biological systems. Photocatalytic treatment is amongst the most efficient technique for phenol removal from aqueous media. In this study, FeTiO3/GO nanocomposite was synthesized through the ultrasound‐assisted method. Structural, morphological, and optical properties of the synthesized nanocomposite were characterized by TEM, XRD, EDS, XPS, BET, TGA, FTIR, and UV–visible techniques. Optimum conditions for phenol photocatalytic degradation were obtained in 3% of GO content, 0.75 g/L nanocomposite dosage, and pH = 8. The degradation efficiency decreased by increasing phenol concentrations and complete mineralization was observed after 240 min of irradiation in optimum conditions. The effect of scavengers indicated that superoxide and hydroxyl radicals had the main role in the photodegradation process. The hindrance effect of inorganic ions was obtained asHCO3- >Cl- > SO42− >NO3-. Our experimental results put forward the FeTiO3/GO nanocomposite as a highly stable catalyst that can successfully remove phenolic compounds from aqueous solutions. Only a 10.8% decrease was observed in phenol degradation efficiency after five cycles, showing high recyclability of the FeTiO3/GO nanocomposite.

Enhancing photodegradation of 2,4,6 trichlorophenol and organic pollutants in industrial effluents using nanocomposite of TiO2 doped with reduced graphene oxide

The present study investigated the applicability of synthesized TiO2@rGO photocatalyst for degradation of organic pollutants from industrial wastewater and photodegradation of 2,4,6 trichlorophenol (2,4,6 TCP) under UV irradiation. The results showed a high reduction in COD and TOC values of industrial effluents reaching 85% and 82%, respectively. Effects of several factors on the photodegradation process such as pH of the solution, TCP initial concentration, irradiation time and catalyst dose were studied. The results proved a high relationship between pH of the solution and the adsorption capacity. The maximum degradation ratio reached up to 90% at pH 6 at the initial concentration of TCP of 50 mg/l when exposed to UV irradiation for 180 min and 0.4 g/L catalyst dose. Kinetic studies indicated that the adsorption process obeyed pseudo-second order model with qe values ranging between 22.0 and 22.7 mg/L and R2 > 0.99. Isotherm model studies showed a good fit with the Langmuir model better than Freundlich model.

Biopolymer-Grafted, Magnetically Tuned Halloysite Nanotubes as Efficient and Recyclable Spongelike Adsorbents for Anionic Azo Dye Removal.

The quest for sustainable development and green chemistry had led to the design and synthesis of advanced adsorbent materials for efficient removal of pollutants in industrial effluents. Magnetic halloysite nanotubes with chitosan nanocomposite sponges were prepared by combining solution-mixing and freeze-drying. Magnetic@chitosan/halloysite (Fe3O4–HNT/CS) and spongelike chitosan/halloysite (HNT/CS) were used as adsorbents for the removal of Congo red dye in aqueous solution in a batch process. The as-prepared composites were characterized using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, vibrating-sample magnetometry, thermal gravimetry–differential scanning calorimetry, and Fourier transform infrared spectroscopy. Data from kinetic study were analyzed with pseudo-first-order and pseudo-second-order models, whereas the mechanism was analyzed using Bangham’s, Elovich’s, intraparticle, and double-exponential diffusion models. The equilibrium data were evaluated using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models. The adsorption kinetics of dye removal followed the pseudo-first-order model with average rate constants of 0.260 and 0.196 min–1 for Fe3O4–HNT/CS and HNT/CS, respectively. The Langmuir adsorption isotherm best fitted the equilibrium data with R2 > 0.9 with maximum adsorption capacities of 41.54 and 54.49 mg g–1 obtained for HNT/CS and Fe3O4–HNT/CS, respectively. Negative values of ΔG° obtained from thermodynamic studies revealed that the adsorption process was spontaneous. The values of ΔH° and ΔS° obtained for Congo red dye removal were 69.46 and 39.54 kJ mol–1 and 240.5 and 145.1 J mol–1 K–1 for HNT/CS and Fe3O4–HNT/CS, respectively. The results indicated that CS–HNT is an excellent adsorbent; however, its magnetic modification further improved its recyclability and enhanced the performance for the removal of Congo red dye from aqueous solution.

English

Phenolic compounds are common pollutants in industrial effluents and pose a significant risk to the environment. The microbial capacity to degrade these molecules makes the prospection of bacteria with this ability very strategic for bioremediation processes in contaminated areas. This study was carried out to isolate bacteria with phenol degrading capacity from Brazilian mangrove soil. Microorganisms were evaluated for tolerance and the ability to use this substance as a single source of carbon. Two bacterial isolates were obtained: MF-1 and MF-2. The microorganisms were identified, respectively, as Bacillus cereus and Bacillus circulans by sequencing the 16S rRNA gene. The isolates exhibited tolerance to phenol at concentrations up to 600 mg.L-1 when grown in Bushnell-Haas Agar (BHA) and 1,500 mg.L-1 in nutrient agar (NA). As for the use of phenol as a single carbon source, the microorganisms were grown in concentrations of 100, 200 and 300 mg.L-1 of the compound. The isolate MF-1 presented a percentage consumption of 22.43, 11.52 and 3.33%, respectively, for each tested concentration. Although there was a decrease in phenol consumption in response to the increased concentration of this substance, bacterial growth was not affected. The best results were obtained for the isolate MF-2, in which consumption of phenol was, respectively, 21.54, 20.54 and 28.85% for these concentrations. Likewise, the increase in phenol concentration caused no reduction in the growth of this isolate.   Key words: Bioremediation, xenobiotic, phenol degrading bacteria, mangrove.

Oxidative Destruction of Organic Pollutants on the Polypropylene Fiber Modified by Nanodispersed Iron

This study aims to solve the problem of deep destruction of organic pollutants in industrial effluents by creating new composite materials with prescribed functional properties. This paper researches the possibility of using composites based on a polypropylene fiber under conditions of photocatalytic degradation of organic pollutants in aqueous and aqueous-organic media. Dye that are water soluble (eosin, brilliant green, rhodamine C) and fat-soluble (blue, yellow and red) have been chosen as organic contaminants. Composites based on the polypropylene fiber have been obtained by introducing nanodispersed iron onto the surface of the initial polymer, using ion implantation and super high frequency irradiation methods. The obtained composites are characterized, and their photocatalytic activity is studied with respect to the pollutants under study in the conditions of the Fenton-like system and visible radiation. The results show that the obtained composite materials are effective catalysts for oxidative photodestruction of organic dyes in aqueous and aqueous-organic media, and their decolorization degree reaches 80–100%.

Efficiency modeling of serial stabilization ponds in treatment of phenolic wastewater by response surface methodology

Phenol is one of the dangerous organic pollutants in industrial effluents, and it has high toxicity and numerous environmental problems. Thus, there is a growing need for more studies on its removal. The goal of this research is to provide a statistical modeling, analysis, and optimization of the simultaneous impact of temperature and phenol concentration on the efficiency of stabilization ponds in treatment of wastewater containing phenol. The experiments were performed using two stabilization ponds at laboratory scales. The experiments were designed by using response surface methodology and Design-Expert software. According to the presented model, optimum removal rate of phenol is achieve when temperature and phenol concentration are 14.20° C and 109.58 mg/l, respectively. The results showed that the removal rate dropped with decreased temperature and increased concentrations of phenol. At 20 °C, by increasing the concentration of phenol from 40 to 130 mg/l, the removal rate dropped from 73 to 45%. Based on this research results, it can be concluded that the stabilization pond had a proper performance in removing phenol, and stabilization ponds can be an alternative for complex and expensive systems.

Immobilization of horseradish peroxidase on electrospun poly(vinyl alcohol)–polyacrylamide blend nanofiber membrane and its use in the conversion of phenol

Electrospun nanofibers, with their porous structures, high surface-to-volume ratio, and good mechanical properties, are used as a support material for enzyme immobilization. In this study, the poly(vinyl alcohol) and polyacrylamide bicomponent (PVA–PAAm) nanofibers were fabricated via the electrospinning method. Synthesized PAAm was characterized with size exclusion chromatography (SEC). Nanofibers were characterized by fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscope (SEM). DSC and TGA analyses showed that the nanofibers were more durable than PVA and PAAm polymers. SEM images demonstrated that all nanofibers possessed uniform and smooth structures (average diameter about 300 nm). FTIR results have shown that PAAm successfully participates in nanofiber structure. The produced nanofibers were used as support material for covalent immobilization of horseradish peroxidase (HRP). The optimum temperature for free HRP was 45 °C, whereas it was 50 °C for the immobilized enzyme. The immobilized HRP showed better storage and thermal stability than free HRP. The kinetic parameters (K m and V max) were found to be 2.42 mM and 0.027 U for the immobilized HRP and 1.86 mM and 0.079 U for the free HRP, respectively. The immobilized enzyme could be used effectively for 25 cycles with 54% retention of the activity. The immobilized HRP was also used for the conversion of phenol. Phenol removal was found to be about 29.68% at 180 min in real wastewater. The novel PVA–PAAm nanofibrous material was successfully used as a support material for covalent immobilization of HRP. Immobilized enzymes such as oxido-reductases onto the PVA–PAAm bicomponent nanofiber could be recommended in the treatment of organic pollutants in industrial effluents.

Surface adsorption and self-assembly of Cu(II) ions on TEMPO-oxidized cellulose nanofibers in aqueous media

TEMPO-mediated oxidized cellulose nanofibers (TOCNFs) have shown potential in the bioremediation of metal ions from contaminated water due to their interaction with positively charged metal ions via electrostatic interactions involving surface carboxyl groups. Copper is one of the most common pollutants in industrial effluents and is thus the target metal in the current study. The specific surface adsorption of Cu(II) was similar for TOCNFs with different degrees of functionalization and directly impacted the zeta potential. SEM imaging of the TOCNF after Cu(II) adsorption revealed interesting nanostructured clusters that were attributable to Cu(II) ions first being adsorbed by carboxylate groups on the TOCNF and subsequently being reduced and self-assembled to Cu(0) nanoparticles (NPs) or copper oxide NPs by microprecipitation. TOCNF turned superhydrophilic and resulted in faster water filtration after copper adsorption due to the stronger polarity of the copper ions or the self-assembled Cu(0) NPs creating voids or highly water-permeable channels at the interface between the interconnected TEMPO-oxidized nanofibers. Thus, the adsorption of Cu(II) ions and self-assembly into the Cu NPs on TOCNF favors a faster water purification process and provides a viable route to reuse/recycle TOCNFs studded with Cu nanoparticles as biocidal materials.

Separation of chromium from water samples using eggshell powder as a low-cost sorbent: kinetic and thermodynamic studies

AbstractChromium is one of the hazardous pollutants in industrial effluents. The aim of this research is to investigate feasibility of using waste eggshells for the removal of Cr(VI) ions from its aqueous solutions. Characterization of crushed and sieved eggshell have been carried out using scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray fluorescence, etc. analysis. The effect of pH, Cr(VI) ions concentration, amount of eggshell, contact time, temperature, etc. parameters have been investigated on the adsorption and it has been found that the maximum removal (about 93%) of Cr(VI) onto eggshells can be achieved at 25°C and pH 5 in 90 min. Freundlich and Langmuir adsorption isotherm models e have been verified using experimental data. Results also include calculation of thermodynamic parameters like, change in enthalpy (ΔH0), change in entropy (ΔS0), and change in free energy (ΔG0) of the ongoing adsorption process. Chromium sorption kinetics is also found to ...

Advanced oxidation (UV-ozone) and cyclodextrin sorption: Effects of individual and combined action on the chemical abatement of organic pollutants in industrial effluents

Among organic pollutants, four families have been listed as priority substances by the European Agency, namely polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), chlorophenols (CPs) and alkylphenols (APs). In this study, sorption onto a non-conventional cyclodextrin-based material alone as well as in combination with advanced oxidation using a UV-ozone process as pre-treatment was applied for the removal of PAHs, VOCs, CPs and APs from industrial effluents. After the various treatments proposed, we present the abatements obtained in the levels of chemical pollution monitored by a complete chemical analysis, and total organic carbon (TOC) and chemical oxygen demand (COD) measurements. High levels of pollutant removal were attained with the combined use of oxidation and sorption. The treatment led to the almost total elimination of organics such as chloroform, 1,2-dichlorobenzene, 2,4,6-trichlorophenol, nonylphenol and phenanthrene. The treatment also lowered TOC and COD by more than 84% and 93%, respectively. This combined lab-scale process using a non-conventional material could constitute an advantageous technology for removing organic pollutants when scaled up to treat polycontaminated industrial effluent.

Catalytic wet-air oxidation processes: A review

Environmental catalysis usually refers to end-of-the-pipe treatment processes that reduce the emissions of hazardous pollutants. Abatement of pollutants in aqueous streams by means of heterogeneous catalysts is an example of such process. This paper reviews the developments in the field of catalytic wet-air oxidation (CWAO). Catalysts are reviewed first, followed by mechanistic speculations and kinetics that have been proposed for the CWAO process. The process is discussed more in detail only in those cases where it is already commercialised or at least foreseen to be in the near future. Particular attention was given to the heterogeneously catalyzed wet-air oxidation of real industrial wastewaters (such as Kraft bleach plant effluents) in batch and continuous-flow oxidation reactors. Finally, the considerable potential of the CWAO process to ultimately destroy organic pollutants in industrial effluents and detoxify them by using novel titania-supported Ru catalysts is presented.