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Chromium is a potentially poisonous and carcinogenic species, which originates from human activities and various industries such as leather, steel, iron, and electroplating industries. Chromium is present in various oxidation states, among which hexavalent chromium (Cr(VI)) is highly toxic as a natural contaminant. Therefore, chromium, particularly Cr(VI), must be eliminated from the environment, soil, and water to overcome significant problems due to its accumulation in the environment. There are different approaches such as adsorption, ion exchange, photocatalytic reduction, etc. for removing Cr(VI) from the environment. By converting Cr(VI) to Cr(III), its toxicity is reduced. Cr(III) is essential for the human diet, even in small amounts. Today, biopolymers such as alginate, cellulose, gum, pectin, starch, chitin, and chitosan have received much attention for the removal of environmental pollutants. Biopolymers, particularly polysaccharides, are very useful compounds due to their OH and NH 2 functional groups and some advantages such as biodegradability, biocompatibility, and accessibility. Therefore, they can be widely applied in catalytic applications and as efficient adsorbents for the removal of toxic compounds from the environment. This review briefly investigates the application of polysaccharide-based (nano)materials for efficient Cr(VI) removal from the environment using adsorption/reduction, photocatalytic, and chemical reduction mechanisms. [Display omitted] • Polysaccharide-based (nano)materials show remarkable potential for the removal of Cr(VI). • Recent studies on the preparation of polysaccharide-based (nano)materials have been reviewed. • Catalytic removal of Cr(VI) has been presented. • Future challenges for the removal of Cr(VI) using polysaccharide-based (nano)materials have been discussed. [ABSTRACT FROM AUTHOR]

Improved wastewater treatment is essential to ensure the health of humans and ecosystems. Wastewater treatment significantly reduces the risk of disease by removing harmful substances from effluent. This work reports the synthesis of a green and efficient heterogeneous magnetic catalyst, based on chitosan as a natural support. For this purpose, we functionalized magnetic chitosan (CuFe 2 O 4 -Ch) with metformin through 3-chloropropyltrimethoxysilane (TMOS) following decoration of this with Cu(II) (CuFe 2 O 4 -Ch-Mtn-Cu(II)). We characterized CuFe 2 O 4 -Ch-Mtn-Cu(II) by FTIR, XRD, SEM, TEM, VSM, TGA/DTG, BET, EDS, and elemental mapping. The synthesized catalyst was applied for room temperature reduction of 4-nitrophenol (4-NP), methylene blue (MB), and rhodamine B (RhB), in the presence of NaBH 4. The reaction times for reduction of the MB, RhB, and 4-NP in the presence the CuFe 2 O 4 -Ch-Mtn-Cu(II) (3 mg in tha case of MB and 4-NP and 5 mg in the case of RhB) are 100 s, 11, and 9 min respectively. The reaction kinetics for the reduction of 4-NP and RhB were investigated and the obtained rate constant, k 4-NP and k RhB were 0.919 and 0.563 min−1 respectively. The synthesized CuFe 2 O 4 -Ch-Mtn-Cu(II) can be recycled and reused 3 times without significant loss of performance. [Display omitted] • CuFe 2 O 4 -Ch-Mtn-Cu(II) as a magnetic heterogeneous catalyst, was synthesized and characterized. • Its catalytic ability was investigated in the reduction and removal of MB, RhB and 4-NP, in the presence of NaBH 4. • The detailed kinetics for the reduction of the pollutants were investigated. • Complete reduction and elimination of MB, RhB, and 4-NP were achieved after 2, 7, and 9 min, respectively. • Easy separation and recyclability of the catalyst are significant features of CuFe 2 O 4 -Ch-Mtn-Cu(II). [ABSTRACT FROM AUTHOR]

Environmental pollution is one of the important concerns for human health. There are different types of pollutants and techniques to eliminate them from the environment. We hereby report an efficient method for the remediation of environmental contaminants through the catalytic reduction of the selected pollutants. A green method has been developed for the immobilization of copper nanoparticles on magnetic lignosulfonate (Cu NPs@Fe 3 O 4 -LS) using the aqueous extract of Filago arvensis L. as a non-toxic reducing and stabilizing agent. The characterization of the prepared Cu NPs@Fe 3 O 4 -LS was achieved by vibrating sample magnetometer (VSM), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD), scanning TEM (STEM), thermogravimetry-differential thermal analysis (TG/DTA), fast Fourier transform (FFT), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron (XPS) analyses. The synthesized Cu NPs@Fe 3 O 4 -LS was applied as a magnetic and green catalyst in the reduction of congo red (CR), 4-nitrophenol (4-NP), and methylene blue (MB). The progress of the reduction reactions was monitored by UV–Vis spectroscopy. Finally, the biological properties of Cu NPs@Fe 3 O 4 -LS were investigated. The prepared catalyst demonstrated excellent catalytic efficiency in the reduction of CR, 4-NP, and MB in the presence of sodium borohydride (NaBH 4) as the reducing agent. The appropriate magnetism of Cu NPs@Fe 3 O 4 -LS made its recovery very simple. The advantages of this process include a simple reaction set-up, high and catalytic antibacterial/antioxidant activities, short reaction time, environmentally friendliness, high stability, and easy separation of the catalyst. In addition, the prepared Cu NPs@Fe 3 O 4 -LS could be reused for four cycles with no significant decline in performance. [Display omitted] • Facile synthesis of magnetic lignosulfonate supported copper nanoparticles. • Efficient reduction of MB, CR and 4-NP using Cu NPs@Fe 3 O 4 -LS catalyst. • Characterization of catalyst by FTIR, XRD, VSM, (HR)TEM, TG/DTA, EDS and XPS. • The catalyst can be reused at least four times with low loss of catalytic ability. • The antibacterial/antioxidant activities of Cu NPs@Fe 3 O 4 -LS were investigated. [ABSTRACT FROM AUTHOR]

Heck cross-coupling reaction (HCR) is one of the few transition metal catalyzed C C bond-forming reactions, which has been considered as the most effective, direct, and atom economical synthetic method using various catalytic systems. Heck reaction is widely employed in numerous syntheses including preparation of pharmaceutical and biologically active compounds, agrochemicals, natural products, fine chemicals, etc. Commonly, Pd-based catalysts have been used in HCR. In recent decades, the application of biopolymers as natural and effective supports has received attention due to their being cost effective, abundance, and non-toxicity. In fact, recent studies demonstrated that biopolymer-based catalysts had high sorption capacities, chelating activities, versatility, and stability, which make them potentially applicable as green materials (supports) in HCR. These catalytic systems present high stability and recyclability after several cycles of reaction. This review aims at providing an overview of the current progresses made towards the application of various polysaccharide and gelatin-supported metal catalysts in HCR in recent years. Natural polymers such as starch, gum, pectin, chitin, chitosan, cellulose, alginate and gelatin have been used as natural supports for metal-based catalysts in HCR. Diverse aspects of the reactions, different methods of preparation and application of polysaccharide and gelatin-based catalysts and their reusability have been reviewed. Current trends, challenges and future prospects exploiting the sustainable applications of chitin, chitosan, starch, cellulose, pectin, alginate, gelatin and gum based (nano)catalysts for the Heck coupling reactions, are highlighted. [Display omitted] • Advances in Heck coupling reactions by biopolymer-based catalysts are described. • Synthetic methods for attaining biopolymer-based catalysts are highlighted. • Catalytic activity of chitin, chitosan, starch, cellulose, pectin, alginate, gelatin and gum based catalysts are presented. • Mechanistic details are provided for Heck coupling reactions using biopolymer-based catalysts. • Future challenges pertaining to Heck coupling reactions using biopolymer-based catalysts are discussed. [ABSTRACT FROM AUTHOR]

The nutrient resources make up a significant portion of wastes from all around the world. According to several recent studies, nuts and their residues are regarded as valuable natural resources for a nutrition and the other applications. The presence of waste nut residues in nature may lead to the environmental problems. The use of this waste for various applications is a very important issue. Nuts contain precious chemicals, which may be advantageous for preparing (nano)materials for the catalytic purposes. Different parts of nuts such as shell, kernel, extracts, etc. have valuable components, which can be used directly to make a variety of heterogeneous catalysts or as stabilising and reducing agents for nanoparticles. For example, the shell of some nuts is rich in lignin, cellulose and hemicellulose, which can be used as an effective and environmentally friendly supports for the heterogeneous catalysts. The design and application of safer and cheaper catalytic systems for different applications including organic synthesis, hydrogen evolution reactions, oxidation reactions, hydrolysis, degradation of pollutants, etc., are an extreme necessity in which nuts and their wastes can play a significant part due to their excellent chemical properties. Cheaper catalysts comprise of natural compounds such as biopolymers, aluminosilicates, kernel shells, zeolites, diatomites, agricultural wastes (such as bagasse pith, rice husk, smaise cob, coconut shell), nut wastes, etc. These compounds are of natural origin and therefore do not harm the environment. Since they are considered a type of waste, they are also cheap and economical. This review for the first time summarises the preparation of (nano)materials from nuts as an environmentally benign resources and their catalytic applications and highlights the industrial benefits and potential applications of these economically sustainable green resources to convert waste to wealth. The recent developments in the synthesis and applications of bio(nano)catalysts in catalytic and environmental areas have been discussed. In this review, the application of nuts as an efficient supports and green reducing agents for the synthesis of nanomaterials has been discussed. Due to the beneficial compounds, which they contain, activated carbon can be extracted from them and used to make heterogeneous catalysts. These bio(nano)catalysts are applied for organic synthesis, hydrogen evaluation reaction (HER), oxidation reactions and hydrolysis for an environmental applications in reduction and degradation of nitro compounds and organic dyes. [Display omitted] • Design and application of safer and cheaper catalytic systems for different applications. • Recent studies on the preparation of nut-derived bio(nano)materials have been reviewed. • Catalytic activities of nut-derived bio(nano)catalysts have been presented. • Application of nut-derived materials for removal of environmental contaminants. • Future challenges on the synthesis of nut-derived bio(nano)materials have been discussed. [ABSTRACT FROM AUTHOR]