Performance of cellulose acetate-ferric oxide nanocomposite supported metal catalysts toward the reduction of environmental pollutants

Exploring the potential of surface-modified alginate beads for catalytic removal of environmental pollutants and hydrogen gas generation

In this study, hydrogel beads were fabricated using alginate (Algt) polymer containing dispersed nickel phthalocyanine (NTC) nanomaterial. The viscous solution of Algt and NTC was poured dropwise into a divalent Ca2+ ions, resulting in the formation of hydrogel beads known as NTC@Algt-BDs. The surface of the NTC@Algt-BDs was further modified by coating them with different types of metal ions, yielding metal-coated M+/NTC@Algt-BDs. The adsorbed metal ions i.e., Cu+2, Ag+, Ni+2, Co+2, and Fe+3 were subsequently reduced to zero-valent metal nanoparticles (M0) by NaBH4. The prepared beads were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Initially, M0/NTC@Algt-BDs were examined for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). Among them, Cu0/NTC@Algt-BDs catalyst exhibited the highest reduction rate and therefore, investigated for reduction of different nitrophenols (NPs) and dyes, including 2-nitrophenol (2-NP), 2,6-dinitrophenol (2,6-DNP), methyl orange (MO), potassium ferrocyanide (PFC), congo red (CR), and acridine orange (ArO). The highest reduction rates of 2.019 and 1.394 min-1 were observed for MO and 2-NP, respectively. Furthermore, the fabricated catalysts were employed for the efficient production of H2 gas by NaBH4 methanolysis. Among which the Ag0/NTC@Algt-BDs catalyst showed excellent catalytic production of H2 gas, exhibiting the lowest activation energy (Ea) of 25.169 kJ/mol at ambient temperature. Furthermore, the impact of NaBH4 amount, and catalyst dosage on the reduction of 2-NP and H2 gas production was conducted whereas the effect of temperature on methanolysis of NaBH4 for evolution of H2 gas was studied. The amount of H2 gas was confirmed by GC-TCD system. Additionally, the recyclability of the catalyst was investigated, as it garnered significant research interest.

Silver oxide doped iron oxide/alginate nanocomposite coated cotton cloth for selective catalytic reduction of potassium ferricyanide

Silver oxide doped iron oxide (Ag2O-Fe2O3) nanocatalyst was prepared and coated on cotton cloth (CC) as well as wrapped in sodium alginate (Alg) hydrogel. Ag2O-Fe2O3 coated CC (Ag2O-Fe2O3/CC) and Ag2O-Fe2O3 wrapped Alg (Ag2O-Fe2O3/Alg) were utilized as catalysts in reduction reaction of 4-nitrophenol (4-NP), congo red (CR), methylene blue (MB) and potassium ferricyanide (K3[Fe(CN)6]). Ag2O-Fe2O3/CC and Ag2O-Fe2O3/Alg were found to be effective and selective catalyst for the reaction of K3[Fe(CN)6]. Further amount of catalyst, K3[Fe(CN)6] quantity, amount of NaBH4, stability of catalyst and recyclability were optimized for the reaction of K3[Fe(CN)6] reduction. Ag2O-Fe2O3/Alg and Ag2O-Fe2O3/CC were appeared to be the stable catalysts by maintaining high activity during recyclability tests showing highest reaction rate constants (kapp) of 0.3472 and 0.5629 min-1, correspondingly. However, Ag2O-Fe2O3/CC can be easily recovered as compared to Ag2O-Fe2O3/Alg by simply removing from the reaction which is the main advantage of Ag2O-Fe2O3/CC. Moreover, Ag2O-Fe2O3/Alg and Ag2O-Fe2O3/CC were also examined in real samples and found useful for K3[Fe(CN)6] reduction involving real samples. The Ag2O-Fe2O3/CC nanocatalyst is a cost and time saving material for economical reduction of K3[Fe(CN)6] and environmental safety.

Metal nanoparticles decorated mint-cellulose acetate composite as an efficient catalyst for the reduction of methyl orange

Water contamination caused by toxic compounds has emerged as one of the most severe challenges worldwide. Biomass-based nanocomposites offer a sustainable and renewable alternative to conventional materials. In this study, a nanocomposite of mint and cellulose acetate (Mint-CA) was prepared and employed as a supportive material for Cu nanoparticles (CuNPs) and Ag nanoparticles (AgNPs). The selectivity of CuNPs@mint-CA and AgNPs@mint-CA was assessed by comparing their performance in the reduction reaction of various dyes solutions. AgNPs@mint-CA exhibited superior catalytic performance, with a removal of 95.2 % for methyl orange (MO) compared to 68 % with CuNPs@mint-CA. The absorption spectra of MO exhibited a distinct peak at 464 nm. The reduction reaction of MO by AgNPs@mint-CA followed pseudo-first-order-kinetic with a rate constant of k = 0.0063 min-1 (R2 = 0.928). The highest removal of MO was achieved under the following conditions: a catalyst weight of 40 mg, an initial MO concentration of 0.07 mM, the addition of 0.5 mL of 0.1 M NaBH4, and a temperature of 25 °C. Furthermore, the AgNPs@mint-CA catalyst exhibited exceptional reducibility even after five use cycles, highlighting its potential for efficiently removing MO.

Catalytic activity of Cu2O nanoparticles supported on cellulose beads prepared by emulsion-gelation using cellulose/LiBr solution and vegetable oil

Nanocatalysts tend to aggregate and are difficult to recycle, limiting their practical applications. In this study, an environmentally friendly method was developed to produce cellulose beads for use as supporting materials for Cu-based nanocatalysts. Cellulose beads were synthesized from a water-in-oil emulsion using cellulose dissolved in an LiBr solution as the water phase and vegetable oil as the oil phase. Upon cooling, the gelation of the cellulose solution produced spherical cellulose beads, which were then oxidized to introduce surface carboxyl groups. These beads (diameter: 95-105 μm; specific surface area: 165-225 m2 g-1) have a three-dimensional network of nanofibers (width: 20-30 nm). Furthermore, the Cu2O nanoparticles were loaded onto oxidized cellulose beads before testing their catalytic activity in the reduction of 4-nitrophenol using NaBH4. The apparent reaction rate constant increased with increasing loading of Cu2O nanoparticles and the conversion efficiency was >90 %. The turnover frequency was 376.2 h-1 for the oxidized cellulose beads with the lowest Cu2O loading, indicating a higher catalytic activity compared to those of other Cu-based nanoparticle-loaded materials. In addition to their high catalytic activity, the cellulose beads are reusable and exhibit excellent stability.

Development of environmentally friendly catalyst Ag-ZnO@cellulose acetate derived from discarded cigarette butts for reduction of organic dyes and its antibacterial applications

The release of harmful organic dyes from different industries besides its degradation products is a major contributor to environmental contamination. The catalytic reduction of these organic pollutants using nanocomposites based on polymeric material presents potential advantages for the environment. In this study, novel nanocomposite based on cellulose acetate (CA)-derived from discharged cigarette butts and zinc oxide nanoparticles (ZnO NPs) was prepared utilizing a very simple and low-cost solution blending method and used as support for silver nanoparticles (Ag NPs). A simple reduction method was used to anchor different percentages of Ag NPs on the ZnO@CA nanocomposite surface via utilizing sodium borohydride as a reducing agent. The Ag-ZnO@CA nanocomposite was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The TEM analysis showed spherical Ag NPs, with an average diameter of ∼17.6 nm, were uniformly anchored on the ZnO@CA nanocomposite surface. The prepared nanocomposites were evaluated as catalysts for the reduction of organic dyes in water. It was found that 10 % Ag-ZnO@CA nanocomposite showed a remarkable reduction of Rhodamine B (RhB), Rhodamine 6G (Rh6G), Methylene Blue (MB), and Sunset Yellow (SY) dyes in short time. In the presence of this nanocomposite, the rate constant, kapp values for RhB, Rh6G, MB, and SY were 0.3498 min-1, 1.51 min-1, 0.2292 min-1, and 0.733 min-1, respectively. This nanocomposite was recovered and reused in five successive cycles, with a negligible loss of its activity. Furthermore, the nanocomposites demonstrated moderate antibacterial activity toward Staphylococcus aureus and Escherichia coli. Thus, this study directed attention on recycling of waste material to a valuable nanocomposite and its applications in environmental protection.

Chitosan hydrogel anchored phthalocyanine supported metal nanoparticles: Bifunctional catalysts for pollutants reduction and hydrogen production

Metal nanoparticles possess high catalytic activity in various organic transformation reactions. A catalyst must be recovered and re-used effectively and economically to lower the overall reaction cost. The recovery of a catalyst remains a challenge due to their extreme small size. In this research work, catalytic metal nanoparticles were synthesized on Zn-phthalocyanine (ZnPc) and chitosan hydrogel (CH) composite which acts as catalyst support. The ZnPc-CH support facilitate the easy recovery of the loaded metal nanoparticles. Metal nanoparticles (M⁰) based on Cu⁰, Ag⁰, Ni⁰, Co⁰ and Fe⁰ were decorated inside and on ZnPc-CH hydrogel surface. The developed M⁰@ZnPc-CH were utilized for the enhanced selective reduction of toxins and hydrogen production by methanolysis and hydrolysis of NaBH₄. Effective catalytic reduction and hydrogen generation was successfully achieved with Co⁰@ZnPc-CH and ZnPc-CH. Under optimized conditions, Co⁰@ZnPc-CH showed complete reduction of 4-nitrophenol (4-NP) in 8.0 min with the fast 4-NP reduction kinetics (K = 0.611 min^-1). Among the developed catalysts, ZnPc-CH showed fast H₂ generation with high H₂ generation rate (HGR = 4100 mLg^-1min^-1) under optimized conditions. Metal leaching from Co⁰@ZnPc-CH was negligible during recycling of the catalyst, suggesting that it could be implemented to 4-NP treatment from real water samples. Similarly, ZnPc-CH could produce same quantity of H₂ throughout 4 continuous cycles of durability testing without any deactivation and leaching and ZnPc-CH showed high stability, indicating the effectiveness of the catalyst to be applied for H₂ production on large scale.

Highly-efficient degradation of organic pollutants by oxalic acid modified sludge biochar: Mechanism and pathways

The application of sludge biochar (SC) materials as efficient catalysts for organic pollutants mineralization via advanced oxidation process meets the good strategy of "make waste profitable". The catalytic oxidations of methyl orange (MO) and pyrene by oxalic acid modified sludge biochar (SC-OA) with and without H₂O₂ were carried out. The analysis of Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), electronic paramagnetic resonance spectrometer (EPR) and free radical quenching experiment were performed and the definite relationships between persistent free radicals (PFRs) type and specific reactive oxygen species (ROS) were made clear. It is suggested for the first time that carbon-centered type PFRs in SC-OA without H₂O₂ could form O₂•^- and •OH from COOH groups, while oxygen-centered type PFRs induced H₂O₂ to produce •OH. The degradation intermediates of MO and pyrene were identified and the transformation pathways were proposed. SC-OA, possessing good sustainable utilization and clean catalytic property, is expected to be popularized and applied in the mineralization of organic pollutants, especially in the in-situ remediation of contaminated soil where is no continuous supply of H₂O₂.

SnLa2O5 wrapped carboxymethyl cellulose mixed calcium alginate nanocomposite beads for efficient reduction of pollutants

In this project, lanthanum oxide doped tin oxide (SnLa₂O₅) nanomaterial was prepared and characterized morphologically and physiochemically by different techniques. The catalytic performance of SnLa₂O₅ was assessed toward catalytic reduction of 4-nitrophenol (4-NP), methyl orange (MO), congo red (CR), methylene blue (MB) and potassium ferricyanide (K₃[Fe(CN)₆]). SnLa₂O₅ was found to be efficient for K₃[Fe(CN)₆] in the presence of NaBH₄, which reduced in only 8.0 min. SnLa₂O₅ was further wrapped in carboxymethyl cellulose mixed calcium alginate (CMC-Alg) hydrogel beads because the powder catalyst cannot be simply recovered from reaction media to recycle and use again. SnLa₂O₅ wrapped CMC-Alg (SnLa₂O₅/CMC-Alg) was assessed for detail analysis of K₃[Fe(CN)₆] reduction. The effect of NaBH₄, K₃[Fe(CN)₆] concentration and amount of catalyst was optimized using SnLa₂O₅/CMC-Alg. The amount of catalyst has positive impact on catalytic reduction of K₃[Fe(CN)₆]. The kinetic study revealed that K₃[Fe(CN)₆] reduction by SnLa₂O₅ and SnLa₂O₅/CMC-Alg was fast, which completed in 8.0 and 4.0 min with rate constant of 0.4283 min^-1 and 0.7461 min^-1, respectively. These findings indicated that the developed SnLa₂O₅/CMC-Alg is best and proficient nanocatalyst for K₃[Fe(CN)₆] reduction. The efficiency along with cost-effective and simple treatment route of the developed nanocatalyst have prospect to compete and replace the reputable commercial catalysts.

Recent advances in the hybridization of cellulose and semiconductors: Design, fabrication and emerging multidimensional applications: A review

Cellulose is a plentiful, biodegradable, renewable, and natural polymer in the world that can be widely utilized in the production of polymer nanocomposites. Cellulose is developed in nanomaterials owing to its remarkable inherent features of low density, non-toxicity, and affordability, as well as the amazing sample characteristics of strength and thermal stability. Recently, there has been a lot of interest in organic-inorganic composites because of their adaptable qualities. Cellulose and semiconductors have exciting properties, and new combinations of both materials may result in efficient functional hybrid composites with distinct properties. Lately, a huge study was reported on cellulose and semiconductor-based nanocomposites. In this review, we summarize the present research development in the preparation methods, structure, features, and possible applications of multifunctional cellulose and semiconductor-based nanocomposites. The cellulose/semiconductor based nanocomposites have massive potential applications in the areas of photodegradation of organic dyes, hydrogen production, metal removal, biomedical, and sensor applications. It is also assumed that this article will promote additional investigation and will establish innovative capabilities to enhance novel cellulose and semiconductor based nanocomposites with new and exciting applications.

A bioresource catalyst system of alginate-starch-activated carbon microsphere templated Cu nanoparticles: Potentials in nitroarenes hydrogenation and dyes discoloration

The evolution and development of solid-matrix are considered a backbone for supporting and stabilizing of metal nanoparticles (NPs) and are the soul of the catalytic system. In the current study, the alginate-starch microsphere (Alg-St) was cross-linked using CaCl₂ as a cross-linker. In addition, the Alg-St microsphere was blended with different percentages of activated carbon (AC). The microspheres adsorbed Cu⁺² was reduced to zero-valent copper NPs through NaBH₄ and used as a dip-catalyst. The supported Cu NPs cum NaBH₄ system was used as dip-catalyst for the hydrogenation of 4-nitrophenol (4NP), 2-nitroanilline (2NA), and degradation of methylene blue (MB) and Congo red (CR) dyes. Among the different kinetics models, the experimental data were well-fitted in the zero-order kinetic model. Moreover pH, and recyclability were studied for 4NP, where the best activity was achieved at pH 7.0 for 4NP. No leaching was observed after 3rd cycle in the catalyst.

Ag nanoparticles anchored on NiO octahedrons (Ag/NiO composite): An efficient catalyst for reduction of nitro substituted phenols and colouring dyes

The development of an efficient sustainable catalyst for effective removal of hazardous chemicals, viz. nitrophenols and organic dyes, from wastewater is a challenging task. Herein, facile synthesis of Ag/NiO composites by anchoring Ag nanoparticles (NPs) on NiO octahedrons with different amounts of Ag NPs (AN-5% (5% Ag), AN-10% (10% Ag) and AN-15% (15% Ag)) has been demonstrated. SEM (scanning electron microscopic) and TEM (transmission electron spectroscopic) images ensured the proper anchoring of spherical Ag NPs (particle size = 16.54 ± 1.88 nm) on octahedron particles of NiO, which was also ensured by XPS (X-ray photoelectron spectroscopy) analysis. Moreover, the resulting composites have an average surface area (49-52 m²g^‒1) and pore size (2.39-2.26 nm). All three synthesized Ag/NiO composites (100 μL) catalyzed the complete reduction of para-np (4-nitrophenol: 0.1587 mM) within 2-3 min in the presence of 0.04 M NaBH₄. Among them, AN-5% has been chosen because of the lowest anchored Ag (5%) to obtain the optimized catalyst's amount (50 μL) and concentration of para-np (0.1587 mM). AN-5% also exhibited excellent catalytic activity towards different nitro substituted phenols, viz. ortho-np (2-nitrophenol), meta-np (3-nitrophenol), para-np (4-nitrophenol) and tri-np (2,4,6-trinitrophenol). AN-5% displayed ∼100% catalytic efficiency for reducing meta-np in 2 min with the apparent first order rate constant (k_app) and normalized rate constant (K_nor) as 1.99 s^-1 and 398.14 s^-1 g^-1, respectively. Additionally, AN-5% (29.41 μg mL^-1) reduced >95% of the colouring dyes (10 ppm) such as CONG-R (congo red: 95% in 6 min), METH-O (methyl orange: 97.5% in 7 min), METH-B (methylene blue: 98.3% in 10 min) and RHOD-B (rhodamine B: 99.2% in 5 min). AN-5% not only demonstrated catalytic reduction towards individual pollutants, but also showed excellent activity for reduction of the mixtures of nitrophenols/dyes and for treatment of simulated industrial effluent samples (EFF1, EFF2) and a real industrial sample (textile dye-bath effluent). AN-5% can also be reused up to several cycles with almost same efficiency and followed the Langmuir-Hinshelwood apparent first order kinetics model.

Copper/Nickel-Decorated Olive Pit Biochar: One Pot Solid State Synthesis for Environmental Remediation

Developing micro- and nanomaterials for environmental pollution remediation is currently a pertinent topic. Among the plethora of strategies, designing supported nanocatalysts for the degradation of pollutants has achieved prominence. In this context, we are addressing one of the UN Sustainable Development Goals by valorizing agrowaste as a source of biochar, which serves as a support for bimetallic nanocatalysts. Herein, olive pit powder particles were impregnated with copper and nickel nitrates and pyrolyzed at 400 °C. The resulting material consists of bimetallic CuNi-decorated biochar. CuNi nanocatalysts were found to be as small as 10 nm and very well dispersed over biochar with zero valent copper and nickel and the formation of copper–nickel solid solutions. The biochar@CuNi (B@CuNi) exhibited typical soft ferromagnet hysteresis loops with zero remanence and zero coercivity. The biochar@CuNi was found to be an efficient catalyst of the reduction in methyl orange (MO) dye, taken as a model pollutant. In sum, the one-pot method devised in this work provides unique CuNi-decorated biochar and broadens the horizons of the emerging topic of biochar-supported nanocatalysts.

Synthesis of zero-valent Au nanoparticles on chitosan coated NiAl layered double hydroxide microspheres for the discoloration of dyes in aqueous medium

The catalyst activity of the nano Au was largely dependent on the particle size and the structure of the supported matrix to avoid particle agglomeration. Chitosan (CS) and CS coated layered double hydroxide of NiAl (LDH) microsphere were designed through a simple and an economic casting method. The CS and LDH microsphere were used for the impregnation and support of Au NPs and represented as Au/CS and Au/LDH and used for the sole and concurrent discoloration of methylene blue (MB) and rhodamine B (RB) dyes. The aim of the incorporation of NiAl-LDH to the CS host polymer is to increase the binding capacity of CS with Au NPs to make it more stable. The Au/LDH displaying stronger catalyst activity for both dyes discoloration, while found highly selective for MB dye. The high catalyst activity of Au/LDH is due to their small crystallite size which is 1.02 nm compared to 6.75 nm in Au/CS derived from Scherer's equation. The k_app value based on zero-order kinetics was higher with Au/LDH against MB and RB dyes which are 3.5 × 10^-1 and 1.4 × 10^-1 min^-1 respectively.

Simultaneous catalytic reduction of p-nitrophenol and hydrogen production on MIL-101(Fe)-based composites

MIL-101(Fe)-based composite materials and their application for the generation of H₂ by the catalytic reduction of nitro organics are reported in this study.

Carboxymethyl cellulose nanocomposite beads as super-efficient catalyst for the reduction of organic and inorganic pollutants

Carboxymethyl cellulose/copper oxide-nickel oxide (CMC/CuO-NiO) nanocomposite beads were prepared by facile, simple and environmentally friendly method. Initially, CuO-NiO was prepared and applied for the catalytic reduction of 4-nitrophenol (4-NP). The results showed that CuO-NiO demonstrate high catalytic activity toward the reduction of 4-NP to 4-aminophenol (4-AP) with a rate constant of 2.97 × 10^-2 s^-1. Further, CuO-NiO were well-dispersed in the polymeric matrix of carboxymethyl cellulose to prepare CMC/CuO-NiO beads. CMC/CuO-NiO nanocomposite beads were also applied to catalyze the reduction of potassium ferrocyanide (K₃Fe (CN)₆), 4-NP, Congo red (CR) and Eosin yellow (EY) in the presence of sodium borohydride. Experimental data indicated that CMC/CuO-NiO nanocomposite has higher catalytic activity and high rate constant compared to CuO-NiO. The rate constant found to be 6.88 × 10^-2, 6.27 × 10^-2, 1.89 × 10^-2 and 2.43 × 10^-2 for K₃Fe(CN)₆, 4-NP, CR and EY, respectively, using 5 mg CMC/CuO-NiO beads. FE-SEM, EDX, FTER, XRD and XPS were used to characterize the nanocomposites. CMC/CuO-NiO beads catalytically reduced up to 95-99% of K₃Fe(CN)₆, 4-NP, CR and EY within 40, 60, 120 and 120 s. CMC/CuO-NiO beads were found more selective for the reduction of 4-NP. The catalytic reduction performance of CMC/CuO-NiO beads was optimized by studying the influence of different parameters on the catalytic reduction of 4-NP. Hence, the effective and super catalytic performance toward the reduction of different organic and inorganic pollutants makes CMC/CuO-NiO beads a smart material and suitable for numerous scientific and industrial applications and may be used as an alternative to high-cost commercial catalysts.

A template of cellulose acetate polymer-ZnAl/C layered double hydroxide composite fabricated with Ni NPs: Applications in the hydrogenation of nitrophenols and dyes degradation

In this work, cellulose acetate polymer (CA) sheet and 2% ZnAl grafted on activated carbon grown in the form of layered double hydroxide (ZnAl/C-LDH) incorporated into CA polymer (CA-ZA2) 5 wt% (CA-ZA5) and 10 wt% of ZnAl/C-LDH (CA-ZA10) sheets were synthesized by simple casting method. All the stated sheets were fabricated with zero-valent Ni nanoparticles by adsorption of Ni⁺² ions followed by subsequent reduction with NaBH₄ and named as CA@Ni, CA-ZA2@Ni, CA-ZA5@Ni, and CA-ZA10@Ni NPs. The synthesized Ni NPs were investigated through FESEM, FTIR, XRD and EDS techniques. These supported and stabilized Ni NPs were largely used for the reduction of 4-nitrophenol (PNP), and 2-nitrophenol (ONP) in the presence of NaBH₄ which act as a reducing agent. Similarly, the catalytic efficiency was also assessed against the removal of dyes. The linear relationship and K_app were obtained from pseudo-first-order kinetics. The rate constant K_app of CA@Ni NPs for the reduction of PNP is 1.5 × 10^-1 and CA-ZA2@Ni (K_app = 2.6 × 10^-1), CA-ZA5@Ni (K_app = 3.2 × 10^-1), and CA-ZA10@Ni is 5.7 × 10^-1 min^-1. The highest rate constant for PNP reduction was observed with CA-ZA10@Ni NPs. The rate of CR removal with ZA10@Ni NPs is 2.05 × 10^-1 while the adjacent R² is 0.9013. Similarly, the rate constant and adjacent R² values were calculated for the degradation of other dyes and nitrophenols.

Pollution, Toxicity and Carcinogenicity of Organic Dyes and their Catalytic Bio-Remediation

Water pollution due to waste effluents of the textile industry is seriously causing various health problems in humans. Water pollution with pathogenic bacteria, especially Escherichia coli (E. coli) and other microbes is due to the mixing of fecal material with drinking water, industrial and domestic sewage, pasture and agricultural runoff. Among the chemical pollutants, organic dyes due to toxic nature, are one of the major contaminants of industrial wastewater. Adequate sanitation services and drinking quality water would eliminate 200 million cases of diarrhea, which results in 2.1 million less deaths caused by diarrheal disease due to E. coli each year. Nanotechnology is an excellent platform as compared to conventional treatment methods of water treatment and remediation from microorganisms and organic dyes. In the current study, toxicity and carcinogenicity of the organic dyes have been studied as well as the remediation/inactivation of dyes and microorganism has been discussed. Remediation by biological, physical and chemical methods has been reviewed critically. A physical process like adsorption is cost-effective, but can't degrade dyes. Biological methods were considered to be ecofriendly and cost-effective. Microbiological degradation of dyes is cost-effective, eco-friendly and alternative to the chemical reduction. Besides, certain enzymes especially horseradish peroxidase are used as versatile catalysts in a number of industrial processes. Moreover, this document has been prepared by gathering recent research works related to the dyes and microbial pollution elimination from water sources by using heterogeneous photocatalysts, metal nanoparticles catalysts, metal oxides and enzymes.

Stabilization of Various Zero-Valent Metal Nanoparticles on a Superabsorbent Polymer for the Removal of Dyes, Nitrophenol, and Pathogenic Bacteria

In this work, a superabsorbent polymer, sodium polyacrylate, also known as water ball (WB), loaded with Ni, Cu, and Ag zero-valent metal nanoparticles (MNPs) was applied for environmental remediation. WBs loaded with Ni, Cu, and Ag NPs were evaluated for their catalytic performance against the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and decolorization of methyl orange (MO), Congo red (CR), and methylene blue (MB) dyes. The apparent rate constants (K app) for the reduction of 4-NP to 4-AP in the presence of Ni, Cu, and Ag NPs were 2.1 × 10-1, 2.9 × 10-1, and 4.6 × 10-1 min-1, respectively, indicating the strongest activity of WB loaded with Ag NPs as compared to the other two catalysts. Similarly, WB loaded with Ag NPs showed the highest K app values compared to the other two catalysts. Among all of the bacteria studied, except Providencia stuartii and Streptococcus mutans, the zone of inhibition of Ag was higher as compared to that of the Ni and Cu NPs, however, slightly low from that of the reference standard tetracycline TE30. Furthermore, the synthesized catalysts were extensively characterized through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS) analyses.

Cellulose acetate-Ce/Zr@Cu0 catalyst for the degradation of organic pollutant

In the present work, Cu nanoparticles were stabilized on ceria/zirconia (Ce/Zr@Cu⁰), cellulose acetate (CA@Cu⁰), and a thin film of cellulose acetate embedded ceria/zirconia (CA-Ce/Zr) designated as CA-Ce/Zr@Cu⁰. In the presence of a reducing agent, all the catalysts revealed excellent catalytic efficiency in aqueous media for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) and degradation of cationic dyes methylene blue (MB) and rhodamine B (RB). Different order of equations were applied to determine the adjacent R² value and rate constant. Adjacent R² values for MB are 9.470, 9.422 and 9.050 and its kapp values per minutes are 1.7 × 10^-1, 8.3 × 10^-2, and 6. 7 × 10^-1 with Ce/Zr@Cu⁰, CA@Cu⁰, and CA-Ce/Zr@Cu⁰ derived from the pseudo 1st order kinetics, while in the absence of catalyst the R² and kapp for MB degradation in the presence of NaBH₄ is 0.8643 and 3.4 × 10^-3 respectively. Furthermore, regression models, ANOVA and correlation coefficients suggested that all the data are highly significant. The synthesized catalysts were applied for the simultaneous reduction/degradation of mixture of 4-NP-MB, 4-NP-RB and 4-NP-MB-RB mixture to check the practical applicability. Catalytic recyclability of CA-Ce/Zr@Cu⁰ catalyst dropped till 5th cycle which is due to the leaching of Cu⁰ NPs.

Airlift bioreactor system for simultaneous removal of hydrogen sulfide and ammonia from synthetic and actual waste gases

The effectiveness of an airlift reactor system in simultaneously removing hydrogen sulfide (H₂S) and ammonia (NH₃) from synthetic and actual waste gases was investigated. The effects of various parameters, including the ratio of inoculum dilution, the gas concentration, the gas retention time, catalyst addition, the bubble size, and light intensity, on H₂S and NH₃ removal were investigated. The results revealed that optimal gas removal could be achieved by employing an activated inoculum, using a small bubble stone, applying reinforced fluorescent light, adding Fe₂O₃ catalysts, and applying a gas retention time of 20 s. The shock loading did not substantially affect the removal efficiency of the airlift bioreactor. Moreover, more than 98.5% of H₂S and 99.6% of NH₃ were removed in treating actual waste gases. Fifteen bands or species were observed in a profile from denaturing gradient gel electrophoresis during waste gas treatment. Phylogenetic analysis revealed the phylum Proteobacteria to be predominant. Six bacterial strains were consistently present during the entire operating period; however, only Rhodobacter capsulatus, Rhodopseudomonas palustris, and Arthrobacter oxydans were relatively abundant in the system. The photosynthetic bacteria R. capsulatus and R. palustris were responsible for H₂S oxidation, especially when the reinforced fluorescent light was used. The heterotrophic nitrifier A. oxydans was responsible for NH₃ oxidation. To our knowledge, this is the first report on simultaneous H₂S and NH₃ removal using an airlift bioreactor system. It clearly demonstrates the effectiveness of the system in treating actual waste gases containing H₂S and NH₃.

Albizia chevalier based Ag nanoparticles: Anti-proliferation, bactericidal and pollutants degradation performance

The eco-friendly biosynthesis of silver nanoparticles (AgNps) from bark extract of Albizia chevalier are reported here for their anti-proliferative, antibacterial and pollutant degradation potentials. The synthesized AgNps were characterized by FTIR spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-rays spectrometry (EDS) and X-ray diffraction studies. The TEM and FESEM images show a monodispersed spherical shaped particles of approximately 30 nm. Crystalline peaks were obtained for the synthesized AgNps in XRD spectrum. The AgNps were investigated for in vitro anticancer and antibacterial activities and its potential to degrade 4-nitrophenol (4-NP) and congo red dye (CR). The MTT results shows a significant dose-dependent antiproliferation effect of the AgNps on the cell lines HepG2, MDA-MB-231 and MFC7. The effect was found more pronounced in MDA-MB-231 as compared to MFC-7 cell lines. The antibacterial results indicated 99 and 95% killing of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) respectively, after 24 h of incubation with the AgNps. The AgNps were found to speed up the reductive degradation of 4-NP and CR dye, which give an alternative route for the removal of toxic organic pollutants from the wastewater. The synthesized AgNps were not only used as a bactericidal and anticancer agent, but also effectively used for the reductive degradation of carcinogenic compounds which are listed as the priority pollutants. Therefore, AgNps have the potential for the treatment of various cancers, bacterial infections and for industrial detoxification of wastewater.