Removal of emerging contaminants daidzein and coumestrol from water by nanozeolite beta modified with tetrasubstituted ammonium cation

Post-fabrication structural changes and enhanced photodegradation activity of semiconductors@zeolite composites towards noxious contaminants

This review article provides the recent progress in semiconductor-based zeolite photoactive materials for the application of noxious contaminants removal. The rapidly expanding industrialization and globalization cause serious threats to the environment or water bodies. The semiconductor@zeolite photocatalysts were implemented for water quality management/sustainment. The exclusive properties of zeolite material have been elaborated with their role in the photocatalysis process. The photoactive material's properties like single-atom catalysts (SACs), distribution of metal in the zeolite crystal were elaborated along with their role in catalytic reactions. Differently prepared semiconductor@zeolite composites such as TiO₂@zeolite, binary and ternary composites, Fe/Ag/bismuth-modified/ZnO/ZnS/NiO/g-C₃N₄/core-shell/quantum dots modified zeolite composites, were systematically summarized. The research progress in morphologies, structural effect, degradation mechanism were recapitulated and tabulated form of % degradation with their optimal parameters such as catalyst dose, pollutant concentrations, pH, light source intensities were also provided. The significance of zeolite frameworks, the structural properties of semiconductor@zeolite photoactive materials to enhance the degradation efficiencies was explored. Analysis of the intermediate products of Norfloxacin, TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), TCDF (2,3,7,8-tetrachlorodibenzofuran), diclofenac contaminants were systematically represented and structurally identified by GC-MS/HPLC-MS techniques.

A review on effective removal of emerging contaminants from aquatic systems: Current trends and scope for further research

Wastewater is water that has already been contaminated by domestic, industrial and commercial activity that needs to be treated before it could be discharged into some other water bodies to avoid even more groundwater contamination supplies. It consists of various contaminants like heavy metals, organic pollutants, inorganic pollutants and Emerging contaminants. Research has been doing on all types of contaminates more than a decade, but this emerging contaminants is the contaminants which arises mostly from pharmaceuticals, personal care products, hormones and fertilizer industries. The majority of emerging contaminants did not have standardized guidelines, but may have adverse effects on human and marine organisms, even at smaller concentrations. Typically, extremely low doses of emerging contaminants are found in the marine environment and cause a potential risk to the aquatic animals living there. When contaminants emerge in the marine world, they are potentially toxic and pose many risks to the health of both man and livestock. The aim of this article is to review the Emerging contaminate sources, detection methods and treatment methods. The purpose of this study is to consider the adsorption as a beneficial treatment of emerging contaminants also advanced and cost effective emerging contaminates treatment methods.

Rapid uptake of atrazine from aqueous phase by thermally activated MCM-41

This study was designed to prepare an adsorbent without any complex modification process for the removal of atrazine (AZN) from aqueous phase. Thus, Mobil composition of matter No. 41 (MCM-41) was synthesized and modified by physical activation at high temperature (650 °C). The synthesized adsorbent was tested by XRD, SEM, EDX, FT-IR and BET to confirm the successful synthesis as well as effectiveness for the adsorption of AZN. The average particle size of prepared material was found to be about 500 nm, while the BET calculations showed that adsorbent was porous with a specific surface area of 25.9 m²/g. Later, it was used in batch removal studies of AZN for which, it showed a high adsorption capacity of 89.99 (mg/g). The pH of 6, temperature of 313 K was found to be the optimized conditions for the maximum removal of AZN. Of the four kinetic models studied, the pseudo-first-order yielded a superior fit in comparison with the other three models. The results indicated that the five linearized adsorption equilibrium isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Harkins-Jura models) closely correlate the AZN adsorption removal process with Pearson correlation coefficient (R²) values of 0.9955, 0.8551, 0.8736, 0.8913 and 0.7253, respectively. The energy functions obtained by thermodynamic analysis suggested that the AZN sorption follows a non-spontaneous and endothermic path.

Nanostructured chitosan/molecular sieve-4A an emergent material for the synergistic adsorption of radioactive major pollutants cesium and strontium

A fresh adsorbent nanostructured chitosan/molecular sieve 4A hybrid (NSC@MS-4A) was fabricated for the rapid adsorption of strontium (Sr²⁺) and cesium (Cs⁺) ions from aqueous solutions. The as-obtained NSC@MS-4A were thoroughly characterized by XRD, FE-SEM, EDS, BET, XPS and FT-IR. The physio-chemical properties and structural aspects revealed that NSC@MS-4A acquires fine surface area (72 m²/g), porous structure as well as compatible functional groups (-P-O-P and -C-O-C) for the admission of Cs⁺ and Sr²⁺ ions. The batch adsorption studies concluded that prepared adsorbent displayed a maximum adsorption of 92-94 % within 40 min. Fast adsorption of Cs⁺ and Sr²⁺ was achieved at neutral pH (6-7), ambient temperature (25-30 °C) and slow agitation speed (50-60 rpm) which could propose vast benefits such as little power utilization and uncomplicated operation. Among six types of adsorption isotherms, Freundlich isotherm showed the best fit with R²>0.997. Pseudo-second order made a better agreement as compare to other kinetic models. The thermodynamic coefficients suggested the passage of Cs⁺ and Sr²⁺ ions through the liquid solid boundary is exothermic and spontaneous. The NSC@MS-4A displayed excellent regenerability properties over five repetitive adsorption/desorption cycles, which specified that as-obtained NSC@MS-4A is a sustainable as well as efficient adsorbent for practical decontamination of radioactive liquid waste.

Complete removal of endocrine disrupting compound and toxic dye by visible light active porous g-C3N4/H-ZSM-5 nanocomposite

Photocatalytic degradation of toxic pollutants is an efficient technique to completely remove the toxic pollutants from water bodies. In the present investigation, photocatalytic degradation of pollutants was studied over porous g-C₃N₄/H-ZSM-5 nanocomposite under visible light irradiation. The composite g-C₃N₄/H-ZSM-5 was synthesized by mixing an aqueous solution of H-ZSM-5 zeolite (increases surface area and provides active sites for degradation) with melamine (precursor of g-C₃N₄) for 10-12 h followed by calcinations at 550 °C. The photocatalyst was characterized by XRD, BET, HRTEM, FESEM, EDS and elemental mapping analysis. These techniques confirmed that, g-C₃N₄/H-ZSM-5 composite have layered and porous structure with uniform distribution of g-C₃N₄ on H-ZSM-5 surface. The BET N₂ adsorption-desorption analysis verified that the catalyst has high surface area (∼175 m²/g) having mesopores and micropores. The prepared catalyst was then used for the photodegradation of a model dye, Methylene Blue (MB) and an endocrine disrupting compound, Fipronil (FIP). Effects of various parameters such as pH, catalyst dose and scavengers were also studied. The % photocatalytic degradation of MB and FIP were around ∼92% and ∼84% with a high rate constants of 0.00997 and 0.00875 min^-1, respectively. From the scavenger study, OH (hydroxyl radical) and radical was found to be the major reactive species for MB and FIP degradation. From these studies it is revealed that, the catalyst is visible active, easy to prepare and an efficient photocatalyst for toxic pollutant degradation.

An ultra-fast non-conventional waste management protocol to recycle of industrial fly ash into zeolite X

An ultra-fast non-conventional waste management protocol was being designed and applied to recycle and reuse industrial coal fly ash (CFA) waste to generate highly pure nanozeolite X. Both microwave heating-assisted hydrothermal treatment method and ultrasonic waves-assisted hydrothermal method have been successfully used for the fast valorization of power plant CFA waste, and the results were compared with conversional valorization method for CFA conversion to zeolite. While conventional methods like hydrothermal treatment using sodium hydroxide took up to 4 days in valorization of the solid CFA waste into a useful zeolitic X material; the non-conventional methods using microwave irradiation of frequency 2.45 GHz and ultrasound irradiation of frequency 20 kHz took 90 min and 20 min respectively to fast-valorize the solid waste into highly pure zeolite material with high cation-exchanged capacity. The unconventional techniques, therefore, can be used in the large-scale valorization of solid waste recycling and reuse to yield highly pure zeolite.

Valorization of coal fly ash into nanozeolite by sonication-assisted hydrothermal method

The study aimed at the recycle and reuse coal fly ash (CFA) via a fast green method. Increasing dependence of coal in power sector results in increased production of CFA, the disposal of which is a major environmental issue. Sonication assisted hydrothermal (UAH) treatment has been employed to convert this CFA into versatile nanozeolite X (NZX) from CFA. The effect of CFA/NaOH, fusion temperature, fusion time and ultrasonication time were investigated. Initial precursor CFA and the synthesized NZX were characterized by XRF, XRD, FESEM, TEM, and FTIR analysis. UAH treatment produced NZX in shorter crystallization time than conventional hydrothermal (CH) method. The particle size of UAH-NZX were obtained from FESEM, BET, TEM analysis as 22-27 nm, 24.36 nm, and 2-5 nm respectively. Average crystal size of UAH-NZX was 21.58 nm as calculated using Scherrer's equation. The optimized condition for the UAH synthesis of NZX was found as CFA/NaOH ratio of 1.25, fusion temperature of 550 °C, fusion time of 1.5 h, and ultrasound time of 20 min. The characteristics of UAH-NZX zeolite was compared with CH-NZX and commercial zeolite X (CZX). The pure NZX was formed by UAH technique with 20 min ultrasound, followed by 6 h hydrothermal treatment at room temperature whereas CH technique took 96 h of hydrothermal digestion at 120 °C. The optimized CEC value of NZX, conventional hydrothermal zeolite X (CH-ZX), and CZX are 428 mmol/100 g, 242 mmol/100 g, and 293 mmol/100 g respectively. The UAH method produced NZX at shorter time with less consumption of energy than CH method with nanozeolite with higher CEC and surface area (797.53 m²/g) than both CH-NZX and CZX. The nanoscale zeolite X can be used efficiently as ion exchanger as well as adsorber.

Adsorption of nicotine in aqueous solution by a defective graphene oxide

Extensive concerns have been focused on the emerging contaminants including nicotine in the aquatic system recently. Graphene oxide (GO) and modified graphene oxides (GO-COOH and defective GO-COOH) are used as effective adsorbents to remove nicotine from aqueous solution. The adsorption isotherms and kinetics of the adsorbents all fit well with Langmuir model and pseudo-second-order model, respectively. The thermodynamic studies show that the adsorption is an exothermic and spontaneous process. The influence of pH and ionic solution strength on the adsorbents is also investigated. The maximum adsorption capacity can be observed at pH value of ca. 8. The adsorption capacities of nicotine are decreased upon the increase of sodium ion concentration. Among all the adsorbents, the defective GO-COOH adsorbents possess the maximum adsorption capacity of nicotine of 196.5 mg g^-1 obtained from Langmuir isotherm. In regeneration experiments, the defective GO-COOH adsorbents can maintain 95.1% of adsorption capacity after five times of cyclic adsorption-desorption processes. The adsorbents are identified by Fourier transform infrared, ¹³C solid-state magic-angle spinning nuclear magnetic resonance, X-ray photoelectron and Raman spectroscopies to determine the adsorption mechanisms and structure on the adsorbents. It can be deduced that the surpassing performance of defective GO-COOH may be ascribed to the unique adsorption mechanism of defects, the enhanced π-π interaction and cation-π bonding. The highly-efficient and stable features enable the defective GO-COOH a promising adsorbent to eliminate nicotine from water.

Rapid ultrasound assisted hydrothermal synthesis of highly pure nanozeolite X from fly ash for efficient treatment of industrial effluent

Nanoporous green materials like nanozeolite has been in focus for their superb efficiency to treat industrial wastewater. The study reports ultrasound assisted hydrothermal method as a very fast method to convert industrial fly ash from different sources of eastern India to nanozeolite X for efficient removal of toxic dyes and metals from industrial effluent. The pure nanosized zeolite X was synthesized rapidly at 20 min of ultrasound treatment after alkali fusion. The efficiency of nanozeolite X was determined in terms of the adsorption capacity towards various divalent ions such as Zn²⁺, Cu²⁺, Cd²⁺, Pb²⁺, Ni²⁺, Ca²⁺, and Mg²⁺ as well as various dyes such as methylene blue, crystal violet, indigo carmine, and Congo red. In comparison to commercially available microporous Zeolite X (a maximum of 120.43 mg g^-1 for Pb²⁺ and 134.62 mg g^-1 by for methylene blue), all synthesized nanozeolite X shows high adsorption capacity for metals (a maximum of 196.24 mg g^-1 for Pb²⁺) as well as dyes (193.45 mg g^-1 for methylene blue). Highly pure nanozeolite X has shown immense potential for treatment of real time industrial wastewater.