Synthesis, characterization, and regeneration of an inorganic-organic nanocomposite (ZnO@biomass) and its application in the capture of cationic dye

Adsorptive Elimination of a Cationic Dye and a Hg (II)-Containing Antiseptic from Simulated Wastewater Using a Metal Organic Framework

Several types of pollutants have acute adverse effects on living bodies, and the effective removal of these pollutants remains a challenge. Safranin O (a biological dye) and merbromin (a topical mercury-containing antiseptic) are considered organic pollutants, and there are only a few reports on their removal. Synthesized and well-characterized (through PXRD, FTIR, FESEM, and EDS analysis) MOF-5 was used for the first time in the removal of safranin O and merbromin from simulated wastewater and real wastewater. In both cases, MOF-5 effectively removed contaminants. We found that in simulated wastewater, the highest efficiency of removal of safranin O was 53.27% (for 15 mg/L) at pH 10, and for merbromin, it was 41.49% (for 25 mg/L) at pH 6. In the case of real wastewater containing natural ions (Na+, K+, F-, Cl-, SO42-, PO43-, Mg2+, and Ca2+) and other molecules, the removal efficiencies of these two dyes decreased (34.00% and 26.28% for safranin O and merbromin, respectively) because of the presence of other ions and molecules. A plausible mechanism for the removal of these pollutants using MOF-5 was proposed.

Facile One-Step Pyrolysis of ZnO/Biochar Nanocomposite for Highly Efficient Removal of Methylene Blue Dye from Aqueous Solution

In this work, we developed a facile one-step pyrolysis method for preparing porous ZnO/biochar nanocomposites (ZBCs) with a large surface area to enhance the removal efficiency of dye from aqueous solution. Peanut shells were pyrolyzed under oxygen-limited conditions with a molten salt ZnCl2, which played the roles of the activating agent and precursor for the formation of nanoparticles. The effects of the mass ratio between the molten salt ZnCl2 and peanut shells as well as pyrolysis temperature on the formation of ZBCs were investigated. Characterization results revealed that the as-synthesized ZBCs exhibited a highly porous structure with a specific surface area of 832.12 m2/g, suggesting a good adsorbent for efficient removal of methylene blue (MB). The maximum adsorption capacity of ZBCs on MB was 826.44 mg/g, which surpassed recently reported adsorbents. The formation mechanism of ZnO nanoparticles on the biochar surface was due to ZnCl2 vaporization and reaction with water molecules extracted from the lignocellulosic structures. This study provides a basis for developing a simple and large-scale synthesis method for wastewater with a high adsorption capacity.

Green Biosynthesis of Zinc Oxide Nanoparticles Using Pluchea indica Leaf Extract: Antimicrobial and Photocatalytic Activities

Nanotechnology is playing a critical role in several essential technologies with nanoscale structures (nanoparticles) in areas of the environment and biomedicine. In this work, the leaf extract of Pluchea indica was utilized to biosynthesize zinc oxide nanoparticles (ZnONPs) for the first time and evaluated for antimicrobial and photocatalytic activities. Different experimental methods were used to characterize the biosynthesized ZnONPs. The biosynthesized ZnONPs showed maximum Ultraviolet-visible spectroscopy (UV-vis) absorbance at a wavelength of 360 nm. The X-Ray diffraction (XRD) pattern of the ZnONPs exhibits seven strong reflection peaks, and the average particle size was 21.9 nm. Fourier-transform infrared spectroscopy (FT-IR) spectrum analysis reveals the presence of functional groups that help in biofabrication. The existence of Zn and O was confirmed by the Energy-dispersive X-ray (EDX) spectrum and the morphology by SEM images. Antimicrobial studies showed that the biosynthesized ZnONPs have antimicrobial efficacy against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus subtilis, Staphylococcus aureus, Candida albicans and Cryptococcus neoformans where inhibition zones at concentration 1000 µg/mL were 21.83 ± 0.76, 13.0 ± 1.1, 14.9 ± 0.85, 24.26 ± 1.1, 17.0 ± 1.0, 20.67 ± 0.57 and 19.0 ± 1.0 mm respectively. Under both dark and sunlight irradiation, the photocatalytic activity of ZnONPs was evaluated towards the degradation of the thiazine dye (methylene blue-MB). Approximately 95% of the MB dye was broken down at pH 8 after 150 min of sunlight exposure. The aforementioned results, therefore, suggest that ZnONPs synthesized by implementing environmentally friendly techniques can be employed for a variety of environmental and biomedical applications.

A comprehensive review on the metal-based green valorized nanocomposite for the remediation of emerging colored organic waste

In today's era, "green" synthesis is an emerging research trend. It has gained widespread attention owing to its dynamic behavior, reliability, simplicity, sustainability, and environment friendly approach for fabricating various nanomaterials. Green fabrication of metal/metal oxides nanomaterials, hybrid materials, and other metal-based nanocomposite can be utilized to remove toxic colored aqueous pollutants. Nanomaterials synthesized by using green approach is considered to be the significant tool to minimize unwanted or harmful by-products otherwise released from traditional synthesis methods. Various kinds of biosynthesized nanomaterials, such as animal waste and plant-based, have been successfully applied and well documented in the literature. However, their application part, especially for the cure of colored organic polluted water, has not been reported as a single review article. Therefore, the current work aims to assemble reports on using novel biosynthesized green metal-based nanomaterials to exclude harmful dyes from polluted water.

Process modelling and techno economic analysis for optimal design of integrated electrocoagulation-membrane system for dye removal in wastewater

Textile industry, one of the largest exporting industries in Malaysia, generates azo dyes wastewater which cannot be easily decomposed biologically due to its high stability and xenobiotic nature. Conventional electrocoagulation (EC) system requires high energy consumption, resulting in higher operating cost while membrane system suffers from fouling. To eliminate these drawbacks, an integrated electrocoagulation - membrane (ECM) system has been proposed as one of the emerging methods for treating dye wastewater. However, feasibility analysis of the proposed system is yet to be conducted. This study proposes a statistical technique to evaluate the techno-economic feasibility of the system via John's Macintosh Project (JMP) software. From JMP, an equation represents the whole model had been obtained for each of the system, EC standalone and ECM system. The models have been validated experimentally it is proven all the models can reach dye removal efficiency of 96%. Overall, the total cost for ECM system (1 V and 1.0 g of NaCl) was 40.44% cheaper than the conventional dye treatment method with total cost of 1.079 million MYR. EC standalone system at 1 V and 1.0 g however were found to be more economically feasible with 0.325 million MYR or 82.07% cheaper compared to conventional photocatalytic method. EC standalone system was also more economical than ECM system due to lower capital cost expended for installation of membrane tank and additional membrane purchase.

Biowaste- and nature-derived (nano)materials: Biosynthesis, stability and environmental applications

Due to the environmental pollution issues and the supply of drinking/clean water, removal of both inorganic and organic (particularly dyes, nitroarenes, and heavy metals) to non-dangerous products and useful compounds are very important transformations. The deployment of sustainable and eco-friendly nanomaterials with exceptional structural and unique features such as high efficiency and stability/recyclability, high surface/volume ratio, low-cost production routes has become a priority; nonetheless, numerous significant challenges/restrictions still remained unresolved. The immobilization of green synthesized metal nanoparticles (NPs) on the natural materials and biowaste generated templates have been analyzed widely as a greener approach due to their environmentally friendly preparation methods, earth-abundance, cost-effectiveness with low energy consumption, biocompatibility, as well as adjustability in various cases of biomolecules as bioreducing agents. Natural and biowaste materials are widely considered as important sources to fabricate greener and biosynthesized types of metal, metal oxide, and metal sulfide nanomaterials using plant extracts. Integrating green synthesized nanoparticles with various biotemplates offers new practical composites for mitigating environmental challenges. In this review, degradation of dyes, reduction of toxic nitrophenols, absorption of heavy metals, and other hazardous/toxic environmental pollutants from contaminated water bodies using biowaste- and nature-derived nanomaterials are highlighted.

Advances in decontamination of wastewater using biomass-basedcomposites: A critical review

Contaminant removal from wastewater using natural biosorbents has been widely studied as a suitable and environmentally benign alternative for conventional techniques. Currently, researchers are working on various biomass-based composites for wastewater remediation to improve the performance of natural biosorbents. This review takes into focus a wide range of biomass-based composites like hydrogel composites, metal oxide composites, magnetic composites, polymer composites, carbon nanotubes (CNTs) and graphene composites, metal organic framework composites (MOFs) and clay composites for the removal of various contaminants from wastewater. It is evident from the literature survey that the composite fabrication involves the modification of morphological and textural features of the biomass which results in significant enhancement of adsorption capacity. Apart from this, regeneration of the used biomass-based composite is also studied in depth in order to overcome the problem of solid waste generation. This review would prove to be beneficial for researchers who are currently focusing on the development of cost-effective, easily available, recyclable biomass-based composites with enhanced adsorption capacities for wastewater treatment.

One-pot synthesis of zinc oxide nanoparticles via chemical precipitation for bromophenol blue adsorption and the antifungal activity against filamentous fungi

In this research, zinc oxide nanoparticles (ZnONPs) were prepared via a facile one-pot chemical precipitation approach and applied in the adsorption of bromophenol blue (BRB) and as antifungal agents against the filamentous fungi and plant pathogens; Alternaria alternata CGJM3078, Alternaria alternata CGJM3006 and Fusarium verticilliodes CGJM3823. The ZnONPs were characterized by the UV-Vis, FTIR, XRD, TGA, BET, SEM, TEM, and EDX techniques, which showed efficient synthesis. The characteristics ZnO UV-Vis absorption band was observed at 375 nm, while the XRD showed an average ZnONPs crystalline size of 47.2 nm. The SEM and TEM images showed an irregular shaped and aggregated porous structure of 65.3 nm average-sized ZnONPs. The TGA showed 22.9% weight loss at 800 °C indicating the high thermal stability of ZnONPs, while BET analysis revealed a surface area, pore volume and pore diameter of 9.259 m2/g, 0.03745 cm3/g and 9.87 nm respectively. The Freundlich, pseudo-second-order, and intra-particle diffusion models showed R2 > 0.9494 and SSE < 0.7412, thus, exhibited the best fit to the isotherm and kinetics models. Thermodynamics revealed feasible, endothermic, random, and spontaneous adsorption of BRB onto the synthesized ZnONPs. The antifungal assay conducted depicts strong antifungal activities against all three tested fungi. Noticeably, ZnONPs (0.002-5 mg/mL) showed maximum activities with the largest zone of inhibition against A. alternata CGJM 3006 from 25.09 to 36.28 mm. This was followed by the strain F. verticilliodes CGJM 3823 (range from 23.77 to 34.77 mm) > A. alternata CGJM3078 (range from 22.73 to 30.63 mm) in comparison to Bleach 5% (positive control). Additionally a model was proposed based on the possible underlying mechanisms for the antifungal effect. This research demonstrated the potent use of ZnONPs for the adsorption of BRB and as effective antifungal agents.

Biogenic and chemically synthesized Solanum tuberosum peel-silver nanoparticle hybrid for the ultrasonic aided adsorption of bromophenol blue dye

This work was aimed at the synthesis of a hybrid (STpe-AgNP), obtained by impregnation of silver nanoparticles (AgNP) onto Solanum tuberosum peel (STpe), for the ultrasonic assisted adsorption of bromophenol blue (BB) dye. SEM, FTIR, XRD, EDX, TGA and BET techniques were used to characterize the adsorbents. The XRD, SEM and EDX confirmed successful impregnation of AgNPs onto STpe to form the hybrid. The AgNPs impregnated onto the hybrid were found to be water stable at various pH values of 2.0-9.0. Chi-square (χ2 < 0.024) and linear regression (R2 > 0.996) showed that the Freundlich model was best fitted among the isotherm models, corroborated by the oriented site model. Kinetic analysis conformed to the intraparticle diffusion and pseudo-first-order rate equations, while thermodynamics displayed a physical, spontaneous and endothermic adsorption process. The presence of competing Pb(II), Ni(II), Cd(II) and Zn(II) metal ions in solution interfered with the adsorption of BB onto the biosorbents. In terms of reusability, STpe and STpe-AgNP showed BB desorption of 91.3% and 88.5% respectively, using NaOH as eluent. Ultra-sonication significantly enhanced the adsorption of BB by both adsorbents, but the impregnation of AgNPs only slightly improved adsorption of the dye from the simulated wastewater. This study also illustrated that pristine STpe biomass waste is a cheap viable option for the decontamination of BB from water.