Green and energy-efficient methods for the production of metallic nanoparticles

In the last decade, researchers paid great attention to the concept of “Green Chemistry”, which aims at development of efficient methods for the synthesis of nanoparticles (NPs) in terms of the least possible impact on human life and environment. Generally, several reagents including precursors, reducing agents, stabilizing agents and solvents are used for the production of NPs and in some cases, energy is needed to reach the optimum temperature for reduction. Therefore, to develop a green approach, researchers had the opportunity to investigate eco-friendly reagents and new energy transfer techniques. In order to substitute the harmful reagents with green ones, researchers worked on different types of saccharides, polyols, carboxylic acids, polyoxometalates and extracts of various plants that can play the role of reducers, stabilizers or solvents. Also, there are some reports on using ultraviolet (UV), gamma and microwave irradiation that are capable of reducing and provide uniform heating. According to the literature, it is possible to use green reagents and novel energy transfer techniques for production of NPs. However, these new synthesis routes should be optimized in terms of performance, cost, product quality (shape and size distribution) and scale-up capability. This paper presents a review on most of the employed green reagents and new energy transfer techniques for the production of metallic NPs

Immobilized laccase on polyimide aerogels for removal of carbamazepine

Since it is known that conventional wastewater treatment plants cannot completely remove pharmaceutical compounds, such as carbamazepine, the need for their removal has intensified. The use of biocatalysts, such as enzyme is an environmentally friendly method for carbamazepine biodegradation. Nevertheless, enzyme immobilization is required to facilitate the recovery and reusability and avoid the loss of enzyme. In this work, laccase was immobilized on modified polyimide aerogels by means of covalent bonding. Results showed that the immobilized laccase on polyimide aerogels possesses significantly improved activity under acidic or basic pH range in comparison with the free enzyme. Furthermore, for all the temperature range the activity of the immobilized enzyme was higher compared to the free enzyme form. The storage stability improved by the immobilization on this support material. The reusability tests towards oxidation of 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) showed that the immobilized laccase maintained 22% of the initial activity after 7 cycles. Immobilized laccase on polyimide aerogels for carbamazepine (CBZ) degradation exhibited 76% and 74% removal in spiked water and secondary effluent, respectively. Furthermore, after 7 cycles the CBZ removal efficiency remained higher (50% and 65% for spiked water and secondary effluent, respectively).Dado que se sabe que las plantas de tratamiento de aguas residuales convencionales no pueden eliminar por completo los compuestos farmacéuticos, como la carbamazepina, se ha intensificado la necesidad de su eliminación. El uso de biocatalizadores, como la enzima, es un método ecológico para la biodegradación de carbamazepina. No obstante, se requiere la inmovilización de la enzima para facilitar la recuperación y reutilización y evitar la pérdida de enzima. En este trabajo se inmovilizó lacasa sobre aerogeles de poliimida modificada mediante enlace covalente. Los resultados mostraron que la lacasa inmovilizada en aerogeles de poliimida posee una actividad significativamente mejorada en un rango de pH ácido o básico en comparación con la enzima libre. Además, para todo el rango de temperatura, la actividad de la enzima inmovilizada fue mayor en comparación con la forma de enzima libre. La estabilidad al almacenamiento mejoró por la inmovilización sobre este material de soporte. Los ensayos de reutilización hacia la oxidación de 2,2′-azino-bis (3-etilbenzotiazolina-6-sulfónico) (ABTS) mostraron que la lacasa inmovilizada mantuvo el 22% de la actividad inicial después de 7 ciclos. La lacasa inmovilizada en aerogeles de poliimida para la degradación de carbamazepina (CBZ) exhibió una eliminación del 76 % y 74 % en agua contaminada y efluente secundario, respectivamente. Además, después de 7 ciclos, la eficiencia de eliminación de CBZ se mantuvo más alta (50 % y 65 % para agua contaminada y efluente secundario, respectivamente). La lacasa inmovilizada en aerogeles de poliimida para la degradación de carbamazepina (CBZ) exhibió una eliminación del 76 % y 74 % en agua contaminada y efluente secundario, respectivamente. Además, después de 7 ciclos, la eficiencia de eliminación de CBZ se mantuvo más alta (50 % y 65 % para agua contaminada y efluente secundario, respectivamente). La lacasa inmovilizada en aerogeles de poliimida para la degradación de carbamazepina (CBZ) exhibió una eliminación del 76 % y 74 % en agua contaminada y efluente secundario, respectivamente. Además, después de 7 ciclos, la eficiencia de eliminación de CBZ se mantuvo más alta (50 % y 65 % para agua contaminada y efluente secundario, respectivamente)

Pine-wood derived nanobiochar for removal of carbamazepine from aqueous media: Adsorption behavior and influential parameters

In recent years, application of biochar for removal of pollutants from aqueous solutions has been of interest due to favorable physicochemical properties and availability of feedstock. However, adsorption behavior has been reported only for raw and micro biochar particles and taking advantage of biochar nanoparticles, which offer superior specific surface area, did not receive any attention. The objective of this study was to investigate the adsorption efficiency of produced nanobiochar from pinewood. For this purpose, removal of carbamazepine (CBZ), a globally prescribed pharmaceutical, at very low concentrations (0.5–20 ppb) on as-produced nanobiochar with average particle size of 60 nm was studied. The results showed that nanobiochar can remove up to 95% of CBZ (74 μg CBZ/g nanobiochar) after 3 h contact time. Adsorption of CBZ on nanobiochar followed Freundlich isotherm model (R2= 0.9822) and pseudo-second order kinetic model (R2= 0.9994). It was found that increasing pH from 3 to 8 can enhance the adsorption efficiency by 2.3 folds. Also, due to the presence of surfactant in wastewater, the addition of Tween 80 as a model surfactant was studied in the range of 0 to 1 (Tween 80 to CBZ molar ratio) and the results showed that adsorption efficiency can be enhanced by 57%. Thus, the nanobiochar obtained from pinewood residues can be a promising sorbent for micropollutants

Green and energy-efficient methods for the production of metallic nanoparticles

In the last decade, researchers paid great attention to the concept of “Green Chemistry”, which aims at development of efficient methods for the synthesis of nanoparticles (NPs) in terms of the least possible impact on human life and environment. Generally, several reagents including precursors, reducing agents, stabilizing agents and solvents are used for the production of NPs and in some cases, energy is needed to reach the optimum temperature for reduction. Therefore, to develop a green approach, researchers had the opportunity to investigate eco-friendly reagents and new energy transfer techniques. In order to substitute the harmful reagents with green ones, researchers worked on different types of saccharides, polyols, carboxylic acids, polyoxometalates and extracts of various plants that can play the role of reducers, stabilizers or solvents. Also, there are some reports on using ultraviolet (UV), gamma and microwave irradiation that are capable of reducing and provide uniform heating. According to the literature, it is possible to use green reagents and novel energy transfer techniques for production of NPs. However, these new synthesis routes should be optimized in terms of performance, cost, product quality (shape and size distribution) and scale-up capability. This paper presents a review on most of the employed green reagents and new energy transfer techniques for the production of metallic NPs

Development of adsorptive membranes by confinement of activated biochar into electrospun nanofibers

Adsorptive membranes have many applications in removal of contaminants, such as heavy metals and organic contaminants from water. Recently, increasing concentrations of pharmaceutically active compounds, especially antibiotics, such as chlortetracycline in water and wastewater sources has raised concerns about their potentially adverse impacts on environment and human health. In this study, a series of polyacrylonitrile (PAN)/activated biochar nanofibrous membranes (NFMs) with different loadings of biochar (0–2%, w/w) were fabricated using electrospinning. The morphology and structure of fabricated membranes was investigated by scanning electron microscopy, Fourier transform infrared and thermogravimetric analysis. The results showed that at 1.5% of biochar loading, the surface area reached the maximum value of 12.4 m2/g and beyond this loading value, agglomeration of particles inhibited fine interaction with nanofibrous matrix. Also, the adsorption tests using chlortetracycline showed that, under environmentally relevant concentrations, the fabricated adsorptive NFMs had a potential for removal of these types of emerging contaminants from water and wastewaters

Pine-wood derived nanobiochar for removal of carbamazepine from aqueous media: Adsorption behavior and influential parameters

In recent years, application of biochar for removal of pollutants from aqueous solutions has been of interest due to favorable physicochemical properties and availability of feedstock. However, adsorption behavior has been reported only for raw and micro biochar particles and taking advantage of biochar nanoparticles, which offer superior specific surface area, did not receive any attention. The objective of this study was to investigate the adsorption efficiency of produced nanobiochar from pinewood. For this purpose, removal of carbamazepine (CBZ), a globally prescribed pharmaceutical, at very low concentrations (0.5–20 ppb) on as-produced nanobiochar with average particle size of 60 nm was studied. The results showed that nanobiochar can remove up to 95% of CBZ (74 μg CBZ/g nanobiochar) after 3 h contact time. Adsorption of CBZ on nanobiochar followed Freundlich isotherm model (R2= 0.9822) and pseudo-second order kinetic model (R2= 0.9994). It was found that increasing pH from 3 to 8 can enhance the adsorption efficiency by 2.3 folds. Also, due to the presence of surfactant in wastewater, the addition of Tween 80 as a model surfactant was studied in the range of 0 to 1 (Tween 80 to CBZ molar ratio) and the results showed that adsorption efficiency can be enhanced by 57%. Thus, the nanobiochar obtained from pinewood residues can be a promising sorbent for micropollutants