Recyclable & highly porous organo-aerogel adsorbents from biowaste for organic contaminants' removal

Selective aerogel has become an attractive adsorbent for removing oil and organic contaminants due to its low density and excellent adsorption capacity. However, aerogels usually use non-sustainable or expensive nanomaterials and require complicated fabrication processes. Herein, using low-cost lignin reclaimed from the biorefinery waste stream as the starting material, we fabricated a highly porous, mechanically strong, and stable aerogel via a simple and one-step method under mild conditions. This aerogel exhibits a controllable micropore structure and achieves quick and efficient adsorption for oil (435% g/g), as well as toxic solvents such as THF (365% g/g). The selective and stable adsorbent can be reused multiple times and the oil adsorption capacity after 5 cycles remained at 89%. This highly efficient, mechanically strong, stable, and regenerable aerogel is a potential candidate for multiple applications such as cleaning up organic contaminants, oil remediation, and oil/water separation. Meanwhile, it also employs a "waste-treat-waste" concept by adding extra value to the biorefinery process for high-efficiency circular bioeconomy.

Optimization of the spontaneous adsorption of food colors from aqueous medium using functionalized Chitosan/Cinnamaldehyde hydrogel

Hydrogels are considered as practical and proficient materials in adsorption and removal of soluble lethal molecules from aqueous system. They are also rapid-decomposable and economical materials besides their diverse preventive claims. In current study, Cinnamaldehyde (C), a natural defensive compound and Chitosan (Ch), natural occurring bio-macromolecule are considered to develop bio-inspired hydrogel (ChC). The structural and surface characteristics of ChC (¹³C solid state NMR, FT-IR, UV-Vis and SEM) are investigated to confirm the successful grafting. The origami of gelation in ChC performs an excellent adsorption activity towards food dyes, Carmoisine (CA) and Tartrazine (TA), which are contaminated by the accumulation during excess release from catering and chemical industries in aqueous system. The adsorption performance is thoroughly screened by varying the pH, ChC dosage, dye concentration, contact time and temperature in aqueous system. Thermodynamic and Kinetics study suggest the natural tendency of adsorption with a good reusability up to 3 cycles. The main mechanism for spontaneous adsorption is initiated by capturing of TA/CA in porous surface followed by the ionic interactions and formation of H-bondings. ChC based adsorption is an excellent and potential approach to control the toxicants for the water-pollution and water-preservation.

A Simple Microextraction Method for Toxic Industrial Dyes Using a Fatty-Acid Solvent Mixture

A mixture of dodecanoic and hexanoic fatty acids was used to perform a simple and efficient microextraction method for industrial dyes such as methylene blue (MB), methyl violet (MV), and malachite green (MG) in aqueous solution. The fatty-acid microextractants were simply mixed and heated until the mixture became homogeneous before adding it to the dye solutions. The fatty-acid solvent and its components were characterized with Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) measurements, while the dye concentrations were measured using UV-Vis spectroscopy. The performance of the extracting mixture was observed to vary across different dye contaminants, dosages of the extractant, concentrations of the dyes, and contact times. High extraction efficiencies of up to ~99% were obtained for MG as well as MV, and ~73% efficiency was achieved for MB. The study shows how a mixture of fatty acids can be used as a simple, efficient, green, and sustainable low-volume method for the removal of toxic industrial dyes in aqueous solutions.

Bio-mass derived functionalized graphene aerogel: a sustainable approach for the removal of multiple organic dyes and their mixtures

Herein, fabrication of a functionalized graphene aerogel (f-GA) from a biomass (pear fruit)-derived graphene aerogel (GA) is described. f-GA is showing better adsorption capacity towards CV, MB and RhB dyes than GA and activated charcoal.

Preparation and catalytic properties of poly(methyl methacrylate)-supported Pd0 obtained from room-temperature, dark reduction of ionic aggregates of the unstable Pd2+ solution ionomer

A poly(methyl methacrylate)-supported Pd⁰ nanocatalyst was successfully prepared from solution reaction of Pd(CH₃COO)₂ with a copolymer acid, poly(methyl methacrylate-ran-methacrylic acid) (MMA–MAA). The reaction was carried out in a benzene/methanol mixed solvent in the dark at room temperature (∼25 °C) in the absence of a typical chemical reductant. There was coordination between the Pd⁰ nanoclusters and MMA–MAA, resulting in Pd⁰ nanoclusters being stably and uniformly dispersed in the MMA–MAA matrix, with an average particle size of ∼2.5 ± 0.5 nm. Mechanistically, it can tentatively be proposed that PMMA-ionomerization of the Pd²⁺ ions produces intramolecular –2COO⁻–Pd²⁺ aggregate cross-links in the solution. On swelling of the chain-segments that are covalently bound via multiple C–C bonds, the resultant elastic forces cause instantaneous dissociation at the O–Pd coordination bonds to give transient bare (i.e., uncoordinated), highly-oxidative Pd²⁺ ions and H⁺-associative carboxylate groups, both of which rapidly scavenge electrons and protons, respectively, of the active α-H atoms abstracted from the methanol molecules of the solvent to make Pd⁰ nanoclusters supported by the re-formed MMA–MAA. The MMA–MAA acid copolymer, without itself undergoing any permanent chemical change, serves as a mechanical activator or catalyst for the mechanochemical reduction of Pd(CH₃COO)₂ under mild conditions. Compared with traditional Pd/C catalysts, this Pd⁰ nanocatalyst exhibited more excellent catalytic efficiency and reusability in the Heck reaction between iodobenzene and styrene, and it could be easily separated. The supported Pd⁰ nanocatalyst prepared using this novel and simple preparation method may display high-efficiency catalytic properties for other cross coupling reactions.

A polymer-supported Pd⁰ nanocatalyst is prepared by using mechanochemical reduction as the driving force for the reaction.

Fibrous Materials Based on Polymeric Salicyl Active Esters as Efficient Adsorbents for Selective Removal of Anionic Dye

To increase the performance efficiency and decrease the costs for organic dye wastewater purification, two fibrous adsorbents based on polymeric salicyl active esters were developed by means of a simple two-step approach. For the first time, salicyl-based active ester polymers were electrospun into fibrous membranes and subsequently postmodified with the desired functional groups under simple and mild reaction conditions. The morphology of the produced fibrous adsorbents was characterized by scanning electron microscopy (SEM), the surface properties were analyzed by nitrogen adsorption/desorption isotherms and contact angle measurements, and the completeness of the postmodification process was determined by Fourier transform infrared (FTIR) and elemental analyses. The adsorbents were further tested for their adsorption and selectivity performance of different organic dyes as well as for their recyclability. To explore the adsorption mechanism, four kinetic models and three isotherm models were used to analyze the adsorption data. The results indicated that the fibrous adsorbents showed an extremely high adsorption capacity for the anionic dye methyl blue. The fibrous adsorbents were also able to selectively adsorb anionic dyes from a mixture of anionic and cationic dyes, and they could be recycled at least 10 times. The simple and cost-efficient development process of these fibrous adsorbents and their excellent performance make them promising materials for further research and application in the area of water treatment.

Investigation of effectiveness of pyrolysis products on removal of alizarin yellow GG from aqueous solution: a comparative study with commercial activated carbon

The increasing use of dyestuff in industrial applications brings with it environmental problems. These dyes, which are an eco-toxic hazard, are common water pollutants, even at very low concentrations in water resources. Therefore, they must be removed in an economical way. In this study, low-cost biosorbents such as pine cone char, walnut shell char, and hazelnut shell char were prepared by pyrolysis process at different carbonization temperatures in the range of 400-700 °C. Biochars with the highest surface area were used to remove alizarin yellow GG from aqueous solution and the adsorption capacities of these materials were compared to commercially available activated carbon. Biomasses and prepared biochars were characterized using Fourier transform infrared spectroscopy, thermogravimetric/differential thermogravimetry analysis, Brunauer-Emmett-Teller (BET), scanning electron microscopy/energy dispersive X-ray spectroscopy, partial and elemental analysis techniques. Operational parameters such as contact time, temperature, pH, adsorbent dosage, and initial dye concentration were considered as variables for the batch adsorption experiments. Among the biochars used, the highest adsorption efficiency (82%) was obtained in pine cone char (BET surface area 259.74 m²/g) at pH = 3, T = 45 °C, adsorbent dosage of 8 g/L, and initial dye concentration of 20 ppm. The adsorption mechanism has been investigated by applying different kinetic and isotherm models with the aid of time-dependent adsorption data. The adsorption process was best described by Langmuir isotherm and pseudo-second order kinetic model.

Diphenylphosphine-Substituted Ferrocene/Silsesquioxane-Based Hybrid Porous Polymers as Highly Efficient Adsorbents for Water Treatment

The study describes the synthesis of two porous hybrid polymers (abbreviated as DPPF-HPP and DPPOF-HPP) from the Friedel-Crafts reaction of octavinylsilsesquioxane with 1,1'-bis(diphenylphosphine)ferrocene (DPPF) and 1,1'-bis(diphenylphosphine oxide)ferrocene (DPPOF), respectively. DPPF-HPP and DPPOF-HPP possess surface areas of about 890 and 780 m² g^-1, respectively, as well as similar pore structures of the coexisting micropores and mesopores. They are excellent materials for high adsorption of different dyes with adsorption capacities of 2280 mg g^-1 for Congo Red and 1440 mg g^-1 for Crystal Violet. DPPF-HPP also shows a strong affinity to adsorb Hg²⁺ ions (300 mg g^-1). These materials show no sign of degradation under repeated cycles and thus offer potential for wastewater treatment.

A new adsorbent of Pb(ii) ions from aqueous solution synthesized by mechanochemical preparation of sulfonated expanded graphite

After the mechanochemical modification, sulfonated functional groups were able to be attached on the surface of SEG effectually, acted a significant role in the adsorption process, the schematic diagram of SEG interacted with Pb(ii) showing as below.