Removal Of Organic Pollutants In Water Research Articles

Elucidating the role of the nanostructure in protein aerogels for removal of organic water pollutants

Access to efficient and affordable materials for water purification is of fundamental importance for the sustainable development of our society. Materials based on protein nanofibrils (PNFs) from agricultural waste- or...

Natural pozzolana as standalone photocatalyst for water treatment

This study focuses on natural pozzolana (volcanic ash) as standalone photocatalyst for removal of organic water pollutants under solar irradiation. Natural pozzolana has been modified and investigated using various techniques (XRD, EDS, FTIR, TGA, and BET surface area). The investigated pozzolana material has worked as metal oxide heterojunctions with SiO2 (35.45 %), Al2O3 (12.56 %), Fe2O3 (14.15 %) and CaO (7.89 %) in a majority, besides other oxides (MgO (5.75 %), TiO2 (3.25 %), Na2O (2.15 %), K2O (1.23 %), and MnO (0.34 %)). The XRD results showed that pozzolana materials contains different crystalline forms such as Albite, Quartz, Biotite, Hematite and Magnesio hornblende. The performance of the prepared pozzolan material has been evaluated for photocatalytic degradation of BPB dye as model water pollutant and the photocatalytic activity was related to the characterization results. It was shown that the sieved pozzolana material (Ps) has the highest photocatalytic degradation rate (0.0175 min−1) compared to raw (P0) and calcined (Pc) samples. The photocatalytic activity of Ps was also higher than that of TiO2 anatase (0.0121 min−1) used under the same experimental conditions, which was attributed to the diversity of pozzolana compositions from various oxides, with a cascade transference of charge carriers leading to effective charge separation and transfer, hence enhancing the photocatalytic activity. Based on this, natural pozzolan could be used as cost effective and green material for sustainable photocatalytic applications.

A non-doped microporous titanosilicate for bimodal adsorption-photocatalysis based removal of organic water pollutants

Access to clean drinking water is limited for millions around the world and lead to dire health and economic ramifications, particularly in developing nations. This study explores a recyclable, low-cost, non-doped, microporous titanosilicate for effective removal of organic water pollutants. Rhodamine B was utilized as a modal pollutant to explore and optimize the activity of the titanosilicate, which evidently occurred via an adsorption and subsequent photocatalytic degradation based bimodal mechanism. The novel titanosilicate has high surface area (SBET of 468 m2/g), is microporous (∼1.3 nm pore diameter), achieved via a surfactant templating technique. Its’ physicochemical properties were characterised using FTIR, Raman, BET, SEM, PXRD and XPS. The photocatalytic activity of the material was studied under a solar simulator via time dependent UV–vis absorption measurements. The material showed 97% removal of Rhodamine B (5 mg/L) within 3 h, and outperformed nanosized titanium dioxide (anatase:rutile 4:1), the most conventionally used photocatalyst in tertiary water treatment. Interestingly, the titanosilicate displayed a dual mechanism of pollutant removal: an initial rapid removal of 59% due to adsorption during a 30 min equilibrating step in the dark, followed by near complete removal within 3 h. Additionally, a >90% efficiency of Rhodamine B removal by the titanosilicate catalyst was achieved consistently throughout 4 cycles, demonstrating its ability for regeneration and reusability. Such activity has not been previously reported in non-doped or non-composite titanosilicates, and opens up pathways to efficient, low-cost water treatment materials, consisting only of environmentally benign raw materials and synthetic procedures.

Visible-light active metal nanoparticles@carbon nitride for enhanced removal of water organic pollutants

Graphitic carbon nitride (gCN) modified with metal nanoparticles (MNPs) has gained great interest as an effective photocatalyst for the photocatalytic removal of organic pollutants from water. Herein, a series of x% Au@gCN and x% Ag@gCN nanohybrids were fabricated via a feasible in-situ reduction/deposition method using non-toxic reducing agents. The prepared MNPs@gCN materials were characterized using several standard characterization and analytical techniques. Their photocatalytic activity toward the degradation of different organic pollutants was studied. The modification of the bulk gCN with MNPs using varying ratios of Au and Ag NPs in the final nanohybrids could improve the visible-light harvesting properties and suppress the photogenerated charges recombination. The 2% Au@gCN and 10% Ag@gCN photocatalysts exhibited a photocatalytic degradation of 98% and 97% of methylene blue (MB) within 20 min of visible light irradiation. The 2% Au@gCN achieved the highest photocatalytic activity with complete degradation of methyl orange (MO) under visible light irradiation for 100 min. Whereas the 10% Ag@gCN showed the highest photodegradation for ciprofloxacin (CIP) upon light exposure. The present work paves a practicable, low-cost, and scalable green approach to fabricate plasmonic gCN-based photocatalysts for superior removal of organic water pollutants under visible light irradiation.

Bio fabrication of 2D MgO/Ag nanocomposite for effective environmental utilization in antibacterial, anti-oxidant and catalytic applications

Top-notch applications related to environment protection is supported by the biologically derived Ag/MgO nanocomposite with green chemistry principles. Ag/MgO nanocomposite fabrication and its validation on their properties were deliberately studied in the current research. Structural and morphological examinations predict the nanocomposite crystalline size to be 32 nm with 2D flakes like morphology. The SPR bands associated with Ag/MgO nanocomposite at 440 nm and 260 nm inferred their strong conjugation in the prepared nanocomposite. Further their contribution to environmental applications like anti-microbial analysis against the bacterial strains were assessed with zone of inhibition assays, anti-oxidant capability is evaluated. Shorter degradation time for catalytic removal of organic water pollutants like Methylene Blue, O-nitrophenol, Methyl Orange and Methyl Violet were addressed with higher efficiencies of 86%, 96%, 95%, 88% within 8 min, 8 min, 6 min and 10 min, respectively. Reusability and stability studies conferred the Ag/MgO bio nanocomposite is highly stable, easily recoverable, recyclable, also nontoxic for the environment. Conclusively green assisted fabrication of Ag/MgO nanocomposite standalone on par with chemically developed nanocomposites in terms of their properties and applications.

A Non-Doped Microporous Titanosilicate for Bimodal Adsorption-Photocatalysis Based Removal of Organic Water Pollutants

A Non-Doped Microporous Titanosilicate for Bimodal Adsorption-Photocatalysis Based Removal of Organic Water Pollutants

Biosynthesis of the ZnO/SnO2 nanoparticles and characterization of their photocatalytic potential for removal of organic water pollutants

Plants are rich sources of antioxidant compounds including phenols and flavonoids. These antioxidants are crucial elements in diet and protect the body against oxidative stress. In this study, antioxidant activity of the phenolic compounds and flavonoids of mistletoe (Viscum album), as a substituent for synthetic antioxidants, was quantitatively investigated. The plant alcoholic (ethanol) extract was used for biosynthesis of the ZnO/SnO2 composite nanoparticles that were employed for photodegradation of three organic pollutants (Congo red (CR), Biphenyl A (BPA), and tetracycline (TC)) under solar light. The photodegradation tests were performed considering the effect of pH, photocatalyst dosage, temperature, and initial concentration of the pollutants. The obtained data were analyzed by a Pseudo-first-order kinetic model. The most optimum conditions for photodegradation of the organic pollutants were found to be: 5 mg/l initial pollutant concentration, 0.5 g/l photocatalyst dosage, and acidic pH. The reusability test implied that the nanoparticles remain stable and can perform well even after 4 cycles of reuse. Conclusively, Viscum album extract offers promising antioxidant properties and allows for biosynthesis of the composite nanoparticles that can optimally photodegrade organic pollutants of wastewater under solar light.

Synthesis of ZnO nanospheres for water treatment through adsorption and photocatalytic degradation: Modelling and process optimization

Here, ZnO nanospheres preparation via simple hydrothermal method has been reported. The physicochemical properties of ZnO nanospheres have been analyzed extensively by using PXRD, SEM, TEM, and DRS techniques. The prepared ZnO nanospheres were utilized as an efficient adsorbent for Bismarck brown (BBR) dye, in batch mode to evaluate the adsorption capacity. The effect of ZnO dosage, concentration of BBR, contact time, pH of solution, and temperature has been studied in detail. Isotherm and kinetic studies have suggested that the BBR adsorption followed Langmuir isotherm giving 10.309 mg/g monolayer capacity and pseudo-second order kinetics with rate constant 0.041 g/mg/min. The free energy values, −4.831, −5.888, and −5.918 kJ/mol at 27, 35, and 45 °C, respectively, confirmed spontaneity the physical nature of BBR sorption onto ZnO nanospheres. The band gap of the prepared ZnO nanospheres was evaluated as 3.22 eV by using Kubelka-Munk equation from DRS technique which established semiconducting nature. The water treatment through the photocatalytic degradation was also performed with and without ZnO nanospheres. The kinetic plot for the photocatalytic degradation of dye indicated the fitting of data to the pseudo-first order kinetic model. Therefore, the synthesized ZnO nanospheres can be photoactive as well as effective adsorbent for the removal of organic water pollutants.

Tea-phytochemicals functionalized Ag modified ZnO nanocomposites for visible light driven photocatalytic removal of organic water pollutants

Biogenic synthesis of semiconductor nanoparticles (NPs) as well as metal-semiconductor nanocomposites (NCs) has become a subject of comprehensive interest and research due to its cost-effective and eco-friendly synthesis approach. In this regard, the current work focuses on the biosynthesis of Zinc oxide (ZnO) NPs and Silver-Zinc oxide (Ag-ZnO) NCs using the leaves extract of tea plant (Camellia sinensis). The as-synthesized samples were characterized by various optical, structural and elemental characterization techniques. The successful capping of tea-phytochemicals were confirmed from the bonding information through Fourier Transform Infrared Spectroscopic analysis, while the formation of ZnO NPs and Ag-ZnO NCs were established using x-ray Diffraction, Energy Dispersive x-ray and x-ray photoelectron spectroscopic techniques. Optical absorbance of ZnO NPs revealed the formation of smaller particle size (∼5.2 nm) as compared to bulk ZnO, while the absorbance of Ag-ZnO NCs depicted the presence of metallic Ag in the sample through surface plasmon resonance. The potential of as-synthesized samples were then tested through the photocatalytic and catalytic degradation of organic water pollutants, such as Methylene blue, Paracetamol drug and para-Nitro phenol. The results indicated that Ag deposition on ZnO nanostructure was beneficial in terms of both catalytic as well as photocatalytic degradation under dark condition and visible light irradiation, respectively. A commercially available light source was used for photodegradation process instead of solar irradiation. In addition, an attempt has also been made to explain the plausible pathway of Ag-ZnO NCs formation by the functionalization of tea-phytochemicals. To the best of Authors’ understanding, this is the first attempt so-far reporting a cost-effective biosynthesis process of Ag-ZnO NCs using tea-extracts and its photocatalytic activity under visible light for the degradation of common organic pollutants.

TiO2-based photocatalytic degradation of 2-chlorophenol adsorbed on hydrophobic clay.

The combination of adsorption and heterogeneous photocatalysis has been investigated as a promising technology for the removal of organic water pollutants. A laboratory study of the removal and decomposition of 2-chlorophenol (2-CP) as a toxic organic pollutant was carried out under various conditions with an organophilized clay mineral (hexadecylpyridinium chloride-modified montmorillonite; HDPM) as adsorbent and Degussa P25 TiO2 as photocatalyst. Three different oxidation processes leading to the degradation of 2-CP were compared: direct photolysis, heterogeneous photocatalysis in a TiO2 suspension, and the decomposition of substrate adsorbed on HDPM in the presence of TiO2. Both the degradation of 2-CP and the formation of intermediates were analyzed by HPLC, the total organic carbon content and the total organic and inorganic chloride contents were measured to monitor the mineralization process, and X-ray diffraction and thermoanalytical measurements were made to characterize the hydrophobic clay adsorbent. The heterogeneous photocatalytic degradation of dissolved (2-CP/UV/TiO2) and desorbed 2-CP (2-CP/HDPM/UV/TiO2) appeared to be equally efficient, whereas direct photolysis of 2-CP was far less efficient in the oxidative destruction. HDPM proved to be a suitable adsorbent, capable of adsorbing toxic organics from water. It was demonstrated that the adsorbent (at relatively high concentration) did not decrease the rate of mineralization of 2-CP. The results confirmed that the adsorbent retains its structure and composition during the mineralization process, and thus it can be reused without regeneration. The combination of adsorption and heterogeneous photocatalysis studied may be an efficient and economical means of accumulating, removing, and oxidizing organic water contaminants, and its application is in accordance with the growing environmental demands.

Influence of ultrasound on adsorption processes

One of the most popular means for removal of organic water pollutants found in small concentrations is by adsorption. An important step in adsorption processes is the regeneration of the adsorbent as it does not only affect the adsorption–desorption cycle but also the expenses of the following process steps. State of the art regeneration of adsorbent resins is done by chemical methods. These require the use of organic solvents or inorganic chemicals and involve a difficult secondary separation step. Therefore, industry seeks for alternative methods to regenerate exhausted adsorbents. One of the discussed regeneration methods is desorption by ultrasound. Ultrasound does not only promote desorption but also enhances the mass transfer of sorption processes. We discuss the arising problems and basic effects when applying ultrasound during sorption processes in order to show the potentials of this desorption process. The focus is laid in particular on the influence of ultrasound frequency and intensity.

Use of high energy radiation in decomposition and removal of organic water pollutants

The present review deals with the radiation chemistry of dilute aqueous solutions of organic substances emphasizing the possibility of use of high energy radiation in wastewater treatment. Effects of radiation on biodegradability, toxicity to water organisms and changes in molecules of solutes showing resistance to biochemical degradation and toxicity to water organisms are discussed.