Silane and fluorine free facile hydrophobicization of water hyacinth biomass for oil-water separations.

As the adverse effects of using plastics and perfluorinated alkyl substances become more apparent, there is a growing need for sustainable hydrophobic products. Cellulose and its derivatives are the most abundant and widely used polymers, and cellulose-based products have great potential in industries where plastics and other hydrophobic polymers are used, such as stain-resistant fabrics, food packaging, and oil-water separation applications. In this study, we extracted cellulose from water hyacinth (WH) biomass, known for its negative environmental impact, and converted it into hydrophobic cellulose. This addresses the issue of managing WH waste and creating an environmentally friendly hydrophobic material. Initially, aldehyde groups were introduced through oxidation with periodate, followed by direct octadecyl amine (ODA) grafting onto dialdehyde cellulose (DAC) via a Schiff base condensation. The resulting ODA modified cellulose (ODA-C) was dispersed in ethanol and used to coat various materials, including cotton fabric, cellulose filter paper, and packaging paper. The modified materials showed excellent hydrophobicity as measured by their water contact angles (WCAs), and the application of the coating was demonstrated for oil-water separation, stain-resistant hydrophobic fabric, and paper-based packaging materials. FTIR, XRD, and WCA analysis confirmed the successful modification of cellulose. A high separation efficiency of 99% was achieved for diesel/water separation using modified filter paper (MoFP), under gravity. On application of the coating, cotton fabric became hydrophobic and resisted staining from dye, and paper-based packaging materials became more robust by becoming water-resistant. Overall, the facile synthesis, low cost, high efficiency, and use of environmentally friendly sustainable materials make this a promising strategy for hydrophobically modifying surfaces for a wide range of applications while reducing the menace of water hyacinth.

Ultrafast adsorption of hexavalent chromium from aqueous effluents using covalent triazine frameworks.

We have synthesized low-cost high performance covalent triazine framework (CTF) through Schiff base reaction of melamine and terephthalaldehyde with different proportions of the reactants. The synthesized adsorbents showed excellent capacity for adsorption of Cr (VI) at acidic pH while almost negligible adsorption at higher pH. The adsorbent displays excellent reusability, with a little decrease in adsorption capacity with the increasing number of cycles. Moreover, Cr (VI) the adsorption is unaffected by the presence of 50-500 times higher concentration of alkali metal and halide ions in solution, while sulphate ions demonstrate shielding behavior decreasing the adsorption capacity. Mechanistic studies indicate electrostatic attractions, ion exchange and reduction being responsible for the adsorption mediated by abundant nitrogen sites that also imbibes the adsorbent with high capacity. The adsorbent was also utilized to recover chromium from an industrial electroplating effluent, which demonstrates applicability of material for practical applications.

An integrated biorefinery approach for the valorization of water hyacinth towards circular bioeconomy: a review.

Water hyacinth (WH) has become a considerable concern for people across the globe due to its environmental and socio-economic hazards. Researchers are still trying to control this aquatic weed effectively without other environmental or economic losses. Research on WH focuses on converting this omnipresent excessive biomass into value-added products. The potential use of WH for phytoremediation and utilizing waste biomass in various industries, including agriculture, pharmaceuticals, and bioenergy, has piqued interest. The use of waste WH biomass as a feedstock for producing bioenergy and value-added chemicals has emerged as an eco-friendly step towards the circular economy concept. Here, we have discussed the extraction of bio-actives and cellulose as primary bioproducts, followed by a detailed discussion on different biomass conversion routes to obtain secondary bioproducts. The suggested multi-objective approach will lead to cost-effective and efficient utilization of waste WH biomass. Additionally, the present review includes a discussion of the SWOT analysis for WH biomass and the scope for future studies. An integrated biorefinery scheme is proposed for the holistic utilization of this feedstock in a cascading manner to promote the sustainable and zero-waste circular bio-economy concept.

Ionic Liquid-Reduced Graphene Oxide Membrane with Enhanced Stability for Water Purification.

There has been a growing interest in water purification by graphene oxide (GO) laminate membranes due to their exceptional hydrophilicity, high throughput, and extraordinary separation performance originating from their two-dimensional and well-defined nanostructure. However, the swelling and stability in an aqueous environment are areas of concern for the GO laminate membranes. Here, a novel methylimidazolium ionic liquid-reduced GO (mimG)-assembled GO laminate membrane (mimG-GO) with remarkable stability was fabricated by a vacuum-assisted strategy for water purification. Methylimidazolium-based ionic liquid-reduced graphene oxide (mimG) was prepared by a facile nucleophilic ring-opening mechanism. Fabricated membranes were thoroughly characterized for stability, structural, permeance, and rejection properties in an aqueous environment. A combination of cationic mimG and GO nanosheets improves membrane stability in the aqueous environment via cation-π interactions and creates nanofluidic channels for facile water transport while yielding significant enhancement in the salt and dye separation performance. The pore size and the number of nanofluidic channels were precisely controlled via material deposition and laminate thickness to remove salts from water. The mimG-GO laminate membrane containing 72.2 mg m-2 deposition showed a permeance of 14.9 LMH bar-1, 50% higher than 9.7 LMH bar-1 of the neat GO laminate membrane, in addition to an increase in Na2SO4 salt rejection from 46.6 to 77.4%, overcoming the flux-rejection trade-off. The mimG-GO laminate membrane also rejected various anionic dyes (i.e., 99.9% for direct red 80 (DR 80), 96.8% for reactive black 5 (RB 5), and 91.4% for methyl orange (MO)). The mimG-GO laminate membrane containing 361.0 mg m-2 deposition showed the highest rejection for Na2SO4 (92.1%) and 99.9% rejection for DR 80, 99.0% rejection for RB 5, and 98.1% rejection for MO dyes keeping a flux of 2.6 LMH bar-1. Partial reduction and covalent grafting of ionic liquid moieties on GO helped to enhance the cation-π interaction between GO laminates, which showed enhanced stability, frictionless water transport, with high salt and dye rejection. Moreover, a simultaneous improvement in water permeance and solute rejection reveals the great potential of ionic liquid-functionalized GO laminate membranes for water-based applications.

Secondary membranes for flux optimization in membrane filtration of biologic suspensions.

We employ in situ deposited secondary membranes of yeast (SMYs) to optimize permeate flux during microfiltration and ultrafiltration of protein solutions. The deposited secondary membrane was periodically removed by backflushing, and a new cake layer was deposited at the start of the next cycle. The effects of backflushing time, backflushing strength, wall shear rate, and amount of secondary membrane deposited on the permeate flux were examined. Secondary membranes were found to increase the permeate flux in microfiltration by severalfold. Protein transmission was also enhanced owing to the presence of the secondary membrane, and the amount of protein recovered was more than twice that obtained during filtration of protein-only solutions under otherwise identical conditions. In ultrafiltration, the flux enhancement owing to the secondary membrane was only 50% or less. In addition, the flux for ultrafiltration was relatively insensitive to changes in the concentration of yeast used during deposition of SMY and to the backflushing strength used to periodically remove the secondary membrane.