Synthesis and characterization of eco-friendly cellulose beads for copper (II) removal from aqueous solutions

Non-derivatizing solvent assisted waste-derived cellulose/ MOF composite porous matrix for efficient metal ion removal: comprehensive analysis of batch and continuous packed-bed column sorption studies

The use of metal-organic frameworks (MOFs) for wastewater treatment in continuous operation is a major challenge. To address this, the present study demonstrates the eco-friendly and economic synthesis of Ca-MOF immobilized cellulose beads (Ca-MOF-CB) derived from paper waste. The synthesized Ca-MOF-CB were characterized using standard analytical techniques. Batch sorption studies were performed to check the effect of cellulose composition (wt%), Ca-MOF loading, contact time, and initial metal ion (Pb2+, Cd2+, and Cu2+) concentration. Ca-MOF-CB beads exhibited outstanding equilibrium sorption capacities for Pb2+, Cd2+, and Cu2+, with estimated values of 281.22 ± 7.8, 104.01 ± 10.58, and 114.21 ± 9.68 mg g-1, respectively. Different non-linear isotherms and kinetic models were applied which confirmed the spontaneous, endothermic reactions for the physisorption of Pb2+, Cd2+, and Cu2+. Based on the highest equilibrium sorption capacity for Pb2+ ion, in-depth parametric column studies were conducted in an indigenously developed packed-bed column set-up. The effect of packed-bed height (10 and 20 cm), inlet flow rate (5 and 10 mL min-1), and inlet Pb2+ ion concentration (200, 300, and 500 mg L-1) were studied. The breakthrough curves obtained at different operating conditions were fitted with the empirical models viz. the bed depth service time (BDST), Yoon-Nelson, Thomas, and Yan to estimate the column design parameters. In order to determine the financial implications at large-scale industrial operations, an affordable synthesis cost of 1 kg of Ca-MOF-CB was estimated. Conclusively, the present study showed the feasibility of the developed Ca-MOF-CB for the continuous removal of metal ions at an industrial scale.

Superadsorbent aerogel based on sunflower stem pith cellulose and layered double hydroxides modified montmorillonite for methylene blue removal from water solution

Sunflower stem pith, an agricultural residue, was used as a starting material for the preparation of bio-based products. Sunflower stem pith nanocellulose (SSP-C) was prepared by sodium hydroxide/urea from the SSP cellulose. The prepared SSP-C was typical of cellulose II. To improve the adsorption capacity of the SSP-C, a bio-based aerogel (SSP-MH) with adsorbed methylene blue (MB) was prepared by compounding layered double hydroxides modified montmorillonite (MH) with SSP-C-based adsorbent, and the chemical characteristics and topology of the adsorbent were determined. The removal performance of SSP-MH in different MB concentrations was examined. Adsorption tests showed that hydrogels containing the same content of MH had higher removal efficiency. The removal rate of MB by SSP-MH was >87.5 % in MB solution (1 g/L), and its maximum adsorption capacity was 263.3 mg/g. The kinetics studies of MB removal were well by quasi-secondary adsorption kinetic model and Langmuir isotherm model. Moreover, the standard free Gibbs energy change of adsorption (ΔG0) was <0, which was favorable for adsorption of MB. The adsorption efficiency of SSP-MH on MB was still above 95 % by the five cycles of the adsorption/desorption experiment. The prepared samples were conducive to the high-value utilization of SSP.

Evaluation of Antifungal Activity of Ag Nanoparticles Synthetized by Green Chemistry against Fusarium solani and Rhizopus stolonifera

Silver nanoparticles (AgNPs) have aroused great interest for applications as fungicides in agriculture. This study reports the synthesis of AgNPs by green chemistry using silver nitrate (AgNO₃) as the precursor agent and a coriander leaf extract as the reducing agent and surfactant. The evaluation of their antifungal properties was carried out when placed in contact with Fusarium solani and Rhizopus stolonifer phytopathogens. The extract and AgNP characterizations were performed using UV-Vis spectroscopy, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), dynamic light scattering (DLS) and scanning electron microscopy (SEM). The evaluation of antifungal properties was carried out by exposing the phytopathogens to different concentrations of AgNPs in PDA (Potato Dextrose Agar). It was found that it was possible to identify the presence of flavones and flavonoids in the extract, compounds that were also involved in the synthesis process of AgNPs. In addition, the UV-Vis analysis of the obtained AgNPs by green chemistry showed resonance peaks at around 428 nm. Furthermore, a high distribution of AgNP sizes, with high concentrations of below 100 nm, was identified, according to DLS measurements. Using SEM images, the information provided by DLS was confirmed, and a crystallite size of 29.24 nm was determined with the help of XRD measurements. Finally, when exposing the phytopathogens to the action of AgNPs, it was concluded that, at a concentration of 1 mg/mL AgNPs, their growth was totally inhibited.

Development of novel and ecological keratin/cellulose-based composites for absorption of oils and organic solvents

Keratin/cellulose cryogels were successfully fabricated using chicken feathers (CF) and cardboard (C) from environmental waste for the first time, to be exploited in oil/solvent absorption. The keratin/cellulose-based composites were obtained by combining the dissolution of CF and C waste in 1-butyl-3-methylimidazolium chloride (Bmim^-Cl⁺) ionic liquid green solvent via regeneration, simply by the freeze-drying method. The characterization analysis of the synthesized keratin/cellulose-based composites was performed using Fourier transform infrared spectrometry, X-ray diffractometry, scanning electron microscopy, and thermogravimetry. The as-prepared cryogel can absorb various oils and organic solvents. Moreover, its sorption capacity can reach up to 6.9-17.7 times the weight of the initial cryogel. This kind of CF/C cryogel revealed good and fast absorption efficiency. It could also be reused by simple absorption/distillation and absorption/desorption methods. Through the kinetic analysis, it was found that the pseudo-second-order model was more appropriate for the keratin/cellulose cryogel oil absorption process. Besides, owing to its low cost, good absorption capacity, and excellent reusability, this cryogel has potential for spill cleanup of oils and organic solvents.

Enhanced Cu(II) adsorption using sodium trimetaphosphate-modified cellulose beads: equilibrium, kinetics, adsorption mechanisms, and reusability

The current study is focused on the simple synthesis of two novel biosorbent beads: BASB/STMP and CNFB/STMP, derived respectively from bleached almond shell (BAS) and cellulose nanofiber from almond shell (CNF) by means of chemical crosslinking with sodium trimetaphosphate (STMP). These biosorbents were thoroughly characterized in terms of structure (FTIR), texture (N₂ adsorption-desorption), thermal behavior (TGA/DTG), morphology (SEM), and surface properties (XPS). The adsorption kinetics of Cu(II) ions onto BASB/STMP and CNFB/STMP materials proved the chemisorption interaction between Cu(II) ions and the STMP functionalized beads. The BASB/STMP equilibrium data were successfully described by the Redlich-Peterson model and the CNFB/STMP data by the Sips model which disclosed maximum adsorption capacities of 141.44 mg g^-1 and 147.90 mg g^-1, respectively. Furthermore, the BASB/STMP bioadsorbent offers easy regeneration and better reusability with high efficiency (> 83%). This study sheds light on the preparation of low-cost adsorbents for wastewater treatment in order to improve the competitiveness and eco-friendliness of agrowaste-based processes.

On the Suitability of Almond Shells for the Manufacture of a Natural Low-Cost Bioadsorbent to Remove Brilliant Green: Kinetics and Equilibrium Isotherms Study

Almond production generates a large number of coproducts, but the farmer's interest mainly focuses on the nutritional and commercial aspects of the kernel for getting the best return from their harvests. Thus, almond coproducts such as almond shells that represent more than 70% of biomass remain underexplored. In this work, the suitability of almond shell powder (ASP) as a natural low-cost adsorbent was evaluated in the adsorption of brilliant green dye (BG), which is known as a chemical pollutant. Brunauer-Emmett-Teller (BET) method, for the determination of specific surface area, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques were performed to characterize the ASP adsorbent. The batch adsorption kinetic study for the removal of BG dye was carried out by varying pH, temperature, initial concentration of the dye, bioadsorbent dose, and contact time. It was found that 98% of BG dye is removed under the following optimal experimental conditions: ASP bioadsorbent dose of 1 g/L at T = 25°C, pH = 6.8, and C 0 = 1 g/L, which proves that ASP can be used as an excellent low-cost bioadsorbent for the removal of BG dye from wastewater. The experimental isotherm data were analyzed using Freundlich and Langmuir models. The results show the best correlation with single-layer adsorption, and the adsorption kinetics seems to follow a pseudo-second-order model.