Purification of dye-contaminated ethanol-water mixture using magnetic cellulose powders derived from agricultural waste biomass

Magnetic Fe3O4 nanoparticles loaded guava leaves powder impregnated into calcium alginate hydrogel beads (Fe3O4-GLP@CAB) for efficient removal of methylene blue dye from aqueous environment: Synthesis, characterization, and its adsorption performance

In the present work, a novel Fe3O4-GLP@CAB was successfully synthesized via a co-precipitation procedure and applied for the removal of methylene blue (MB) from aqueous environment. The structural and physicochemical characteristics of the as-prepared materials were explored using a variety of characterization methods, including pHPZC, XRD, VSM, FE-SEM/EDX, BJH/BET, and FTIR. The effects of several experimental factors on the uptake of MB using Fe3O4-GLP@CAB were examined through batch experiments. The highest MB dye removal efficiency of Fe3O4-GLP@CAB was obtained to be 95.2 % at pH 10.0. Adsorption equilibrium isotherm data at different temperatures showed an excellent agreement with the Langmuir model. The adsorption uptake of MB onto Fe3O4-GLP@CAB was determined as 136.7 mg/g at 298 K. The kinetic data were well-fitted by the pseudo-first-order model, indicating that physisorption mainly controlled it. Several thermodynamic variables derived from adsorption data, like as ΔGo, ΔSo, ΔHo, and Ea, accounted for a favourable, spontaneous, exothermic, and physisorption process. Without seeing a substantial decline in adsorptive performance, the Fe3O4-GLP@CAB was employed for five regeneration cycles. Because they can be readily separated from wastewater after treatment, the synthesized Fe3O4-GLP@CAB was thus regarded as a highly recyclable and effective adsorbent for MB dye.

Preferential, synergistic sorption and reduction of Cr(VI) from chromium-rhodamine B mixed wastewater by magnetic porous biochar derived from wasted Myriophyllum aquaticum biomass

Eradication of heavy metals and dyes simultaneously from wastewater is urgently needed to safeguard public and environmental health. In this study, magnetic porous biochar derived from wasted Myriophyllum aquaticum (MPMaB) was synthesized by KOH-activation and co-precipitation method to treat chromate and rhodamine B (RhB)-bearing wastewater. The KOH activation significantly improved the pore structure of biochar with a high specific surface area of 937.1 m² g^-1. The sorption performance of MPMaB for Cr(VI) and RhB in single and co-solutes conditions was evaluated. In single system, a pH-dependent sorption pattern for Cr(VI) by MPMaB was revealed and the estimated sorption capability reached 175.4 mg g^-1, whereas the Langmuir-based sorption capacity of RhB was 175.4 mg g^-1 pH-independently. MPMaB partially transformed Cr(VI) to less toxic Cr(III) (approximately 59.3%). Synergistic sorption of Cr(VI) with the coexistence of RhB was observed, where synergistic effect ranged from 119% to 527% depending on pH. For example, the sorption capacity of Cr(VI) on MPMaB, at pH 2, augmented from 175.4 mg g^-1 (single system) to 208.3 mg g^-1 (binary system). Preferential sorption of Cr(VI) was found and was further confirmed by the post-sorption of Cr(VI) (or RhB) by MPMaB pre-sorbed with RhB (or chromate). Chromate sorption mechanisms mainly include electrostatic interactions and complexation, while the sorption of RhB is ascribed to π-π interactions, pore filling and hydrogen bonding. Additionally, MPMaB showed excellent reusability and maintained high removal efficiency after 5 cycles. In short, MPMaB can efficiently treat chromium and dyes-containing wastewater as sustainable and environmentally friendly adsorbent.

Oil/water separation using elastic bio-aerogels derived from bagasse: Role of fabrication steps

Bio-aerogels hold great promise for selective oil separation from water due to their light weight and high sustainability. However, how the fabrication methods impact the elasticity and oil sorption performance of bio-aerogels still needs systematic comparison and in-depth investigation. In this study, the fabrication of hydrophobic bio-aerogels with good elasticity and reusability was optimized using a factorial design based on the dosages of bagasse-derived cellulose nanofiber, sodium alginate, and calcium carbonate. The role of each key fabrication step, including ice-templating, calcium crosslinking, solvent dehydration, freeze-drying, and silanization, played in the material properties was also elucidated. The optimized bio-aerogels had a low density (7.55 mg/cm³), high porosity (99.47%), large specific surface area (39 m²/g), and strong hydrophobicity (water contact angle of 135°). In addition, the bio-aerogels exhibited outstanding selective oil separation ability towards the oil-water mixture, with oil sorption capacity of 89-126 times its weight. The in-situ calcium crosslinking and solvent dehydration were vital to create porosity and preserve the microstructure of the bio-aerogels. The chemical vapor deposition rendered the bio-aerogels hydrophobic and oleophilic, greatly enhancing the separability of oil from the water-oil mixture.

A Flexible and Weavable Lignocellulose-Based Photocatalyst Supported by Natural Three-Dimensional Porous Juncus effusus for Highly Efficient Degradation of Environmental Contaminants

Lignocellulosic biomass is a potential biotemplate for disposing the burden of the uncontrollable accumulation of environmental contaminants disrupting the hydrophytic ecosystems. Herein, an efficient solar-driven catalyst was prepared using a natural three-dimensional (3D) porous lignocellulose-based Juncus effusus (JE) fiber for wastewater treatment. Owing to the exquisite 3D microstructure and abundant hydroxyl groups, the two-dimensional lamellar graphitic carbon nitride/graphene oxide (g-C₃N₄/GO) nanocomposites were successfully synthesized and decorated on the carboxymethylated JE fiber via the electrostatic self-assembly method. The as-prepared g-C₃N₄/GO-JE (CNG-JE) photocatalyst exhibits excellent light absorption efficiency and a superior ability to accelerate photogenerated electron migration. The outstanding adsorption performance toward pollutants also contributes to the photodegradation property of CNG-JE, showing highly efficient degradation of C.I. Reactive Red 120 (99.8%), C.I. Acid Yellow 11 (99.8%), methylene blue (99.4%), Cr(VI) (98.8%), and tetracycline (87.2%). Most importantly, the lignocellulose-based CNG-JE fibers could be fabricated into a photocatalyst textile due to their flexible and weavable properties. In actual application, the CNG-JE textile can be reused for at least five cycles under the sun, demonstrating that the flexible CNG-JE textile is practical and recyclable. This study may provide a platform for constructing efficient, flexible, and weavable biomass-based porous materials for cost-effective and sustainable catalytic applications.

Efficient adsorption of methylene blue on carboxylate-rich hydrochar prepared by one-step hydrothermal carbonization of bamboo and acrylic acid with ammonium persulphate

Hydrochar (AAHC) with rich carboxylate groups was prepared by one-step hydrothermal carbonization (HTC) of bamboo and acrylic acid with the presence of ammonium persulphate, and then activated by a sodium hydroxide solution. AAHC was featured by elemental analysis, SEM, XPS, FTIR, Zeta potential analysis and N₂ adsorption-desorption isotherms, and applied to test adsorptive ability of methylene blue (MB) by batch sorption experiments. Despite a small Brunauer-Emmett-Teller (BET) surface area of 5.03 m²·g^-1, AAHC has excellent MB adsorbing capacity owing to the richness of carboxylate groups. Compared with hydrochar produced without adding ammonium persulphate, AAHC exhibits larger BET surface, pore volume and carboxylate groups, indicating a small amount of ammonium persulfate plays an important role in HTC in addition to the free radical initiator. This work provides a facile and cheap method combining HTC and polymerization for preparation of carboxylate-rich hydrochar.

Efficient removal of methylene blue by activated hydrochar prepared by hydrothermal carbonization and NaOH activation of sugarcane bagasse and phosphoric acid

Activated-hydrochar (AHC) derived from sugarcane bagasse was synthesized by hydrothermal carbonization (HTC) using phosphoric acid and sodium hydroxide (NaOH) as activators. The properties of AHC were systematically characterized by elemental analysis, BET, SEM, FTIR, XPS and zeta potential, and applied to evaluate the adsorption ability of methylene blue (MB) by batch adsorption tests. The MB adsorption isotherm and kinetics of AHC were well described by the Langmuir model and pseudo-second-order kinetic model. Characteristic analysis suggested electrostatic attraction, hydrogen bonding and π-π interactions were the main contributors to MB adsorption. Analysis of mass transfer mechanisms demonstrated the adsorption process towards MB by AHC involved intra-particle diffusion to some extent. Thermodynamic studies indicated MB adsorption was an endothermic, spontaneous process associated with a disorder increase at the solid-liquid interface. The maximum adsorption capacity of AHC for MB was 357.14 mg g-1 at 303 K. Thus, the combination of HTC in phosphoric acid and NaOH activation offered a facile, green and economical alternative for conversion of sugarcane bagasse into efficient adsorbents used in wastewater treatment.