Phosphorylating Tannin in Urea System: A Simple Approach for Enhanced Methylene Blue Removal from Aqueous Media.

Tannin, after lignin, is one of the most abundant sources of natural aromatic biomolecules. It has been used and chemically modified during the past few decades to create novel biobased materials. This work intended to functionalize for the first time quebracho Tannin (T) through a simple phosphorylation process in a urea system. The phosphorylation of tannin was studied by Fourier transform infrared spectroscopy (FTIR), NMR, inductively coupled plasma optical emission spectroscopy (ICP-OES), and X-ray fluorescence spectrometry (XRF), while further characterization was performed by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and thermogravimetric analysis (TGA) to investigate the morphology, composition, structure, and thermal degradation of the phosphorylated material. Results indicated the occurrence of phosphorylation, suggesting the insertion of phosphate-containing groups into the tannin structure, revealing a high content of phosphate for modified tannin (PT). This elevated phosphorus content serves as evidence for the successful incorporation of phosphate groups through the functionalization process. The corresponding PT and T were employed as adsorbents for methylene blue (MB) removal from aqueous solutions. The results revealed that the Langmuir isotherm model effectively represents the adsorption isotherms. Additionally, the pseudo-second-order model indicates that chemisorption predominantly controls the adsorption mechanism. This finding also supports the fact that the introduced phosphate groups via the phosphorylation process significantly contributed to the improved adsorption capacity. Under neutral pH conditions and at room temperature, the material achieved an impressive adsorption capacity of 339.26 mg·g-1 in about 2 h.

Hybrid carbonaceous adsorbents based on clay and cellulose for cadmium recovery from aqueous solution.

The current work describes the synthesis of carbonaceous composites via pyrolysis, based on CMF, extracted from Alfa fibers, and Moroccan clay ghassoul (Gh), for potential use in heavy metal removal from wastewater. Following synthesis, the carbonaceous ghassoul (ca-Gh) material was characterized using X-ray fluorescence (XRF), Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM-EDX), zeta-potential and Brunauer-Emmett-Teller (BET). The material was then used as an adsorbent for the removal of cadmium (Cd2+) from aqueous solutions. Studies were conducted into the effect of adsorbent dosage, kinetic time, initial concentration of Cd2+, temperature and also pH effect. Thermodynamic and kinetic tests demonstrated that the adsorption equilibrium was attained within 60 min allowing the determination of the adsorption capacity of the studied materials. The investigation of the adsorption kinetics also reveals that all the data could be fit by the pseudo-second-order model. The Langmuir isotherm model might fully describe the adsorption isotherms. The experimental maximum adsorption capacity was found to be 20.6 mg g-1 and 261.9 mg g-1 for Gh and ca-Gh, respectively. The thermodynamic parameters show that the adsorption of Cd2+ onto the investigated material is spontaneous and endothermic.

Manufacturing of macroporous cellulose monolith from green macroalgae and its application for wastewater treatment.

Enormous interest in using marine biomass as a sustainable resource for water treatment has been manifested over the past few decades. Herein, the objective was to investigate the possible use of green macroalgae (Codium tomentosum) for cellulose-based foam production through a versatile and convenient process. Macroporous cellulose monolith was prepared from cellulose hydrogel using freeze-drying process, resulting in a mechanically rigid monolith with a high swelling ratio. The as-produced spongy-like porous cellulosic material was used as bio-sorbent for wastewater treatment, particularly for removing methylene blue (MB) dye from concentrated aqueous solution. The adsorption capacity of MB was subsequently studied, and the effect of adsorption process parameters was determined in a controlled batch system. From the kinetic studies, it was found that the adsorption equilibrium was reached within 660 min. Furthermore, the analysis of the adsorption kinetics reveals that the data could be fitted by a pseudo-second order model, while the adsorption isotherm could be described by Langmuir isotherm model. The maximum adsorption capacity was found to be 454 mg/g. The findings suggested that the produced cellulose monolith could be used as a sustainable adsorbent for water treatment.

Production of cellulose nanocrystals from vine shoots and their use for the development of nanocomposite materials.

In the present work, cellulose nanocrystals (CNC) were produced from vine shoots waste using chemical treatments followed by acid hydrolysis process. FTIR analysis confirmed that the non-cellulosic components were progressively removed during the chemical treatments, and the final obtained materials are composed of pure cellulose. AFM and TEM observations showed that the extracted CNC possess a needle-like shape with an average length of 456 nm and an average diameter of 14 nm, giving rise to an average aspect ratio of about 32. The as-extracted CNC exhibit a cellulose I structure with high crystallinity index (82%), as determined by XRD characterization. Importantly, the resulted CNC provide a higher thermal stability in comparison with CNC extracted from other resources, using the same extraction process. The isolated CNC's surface charge density was evaluated by XPS analysis and resulted in ~2.0 sulfate groups per 100 anhydroglucose units. In order to identify the reinforcing ability of the new extracted CNC, Carboxymethyl cellulose nanocomposite films were prepared with various CNC contents (1, 3, 5, 8 wt%) and their mechanical properties were investigated by uniaxial tensile test. The results showed that the as-extracted CNC displayed a higher reinforcing ability for nanocomposite materials.

Reuse of red algae waste for the production of cellulose nanocrystals and its application in polymer nanocomposites.

Red algae is widely available around the world and its exploitation for the production of agar products has become an important industry in recent years. The industrial processing of red algae generates a large quantity of solid fibrous wastes, which constitutes a source of serious environmental problems. In the present work, the utilization of red algae waste as raw material to produce high-quality cellulose nanocrystals (CNC) has been investigated, and the ability of the as-isolated CNC to reinforce polymer has been studied. Red algae waste was chemically treated via alkali, bleaching and acid hydrolysis treatments, in order to obtain pure cellulose microfibers and CNC. The raw waste and the as-extracted cellulosic materials were successively characterized at different stages of treatments using serval analysis techniques. It was found that needle-like shaped CNC were successfully isolated at nanometric scale with diameters and lengths ranged from 5.2±2.9 to 9.1±3.1nm, and from 285.4±36.5 to 315.7±30.3nm, respectively, and the crystallinity index ranged from 81 to 87%, depending on the hydrolysis time (30, 40 and 80min). The as-extracted CNC were used as nanofillers for the production of polyvinyl alcohol (PVA)-based nanocomposite films with improved thermal and tensile properties, as well as optical transparency. It is shown that the addition of 8wt% CNC into the PVA matrix increased the Young's modulus by 215%, the tensile strength by 150%, and the toughness by 45%. Additionally, the nanocomposite films maintained the same transparency level of the neat PVA film (transmittance of ∼90% in the visible region), suggesting that the CNC were dispersed at the nanoscale.

Processing and properties of eco-friendly bio-nanocomposite films filled with cellulose nanocrystals from sugarcane bagasse.

Novel synthesis strategy of eco-friendly bio-nanocomposite films have been exploited using cellulose nanocrystals (CNC) and polyvinyl alcohol/carboxymethyl cellulose (PVA/CMC) blend matrix as a potential in food packaging application. The CNC were extracted from sugarcane bagasse using sulfuric acid hydrolysis, and they were successfully characterized regarding their morphology, size, crystallinity and thermal stability. Thereafter, PVA/CMC-CNC bio-nanocomposite films, at various CNC contents (0.5-10wt%), were fabricated by the solvent casting method, and their properties were investigated. It was found that the addition of 5wt% CNC within a PVA/CMC increased the tensile modulus and strength by 141% and 83% respectively, and the water vapor permeability was reduced by 87%. Additionally, the bio-nanocomposites maintained the same transparency level of the PVA/CMC blend film (transmittance of ∼90% in the visible region), suggesting that the CNC were dispersed at the nanoscale. In these bio-nanocomposites, the adhesion properties and the large number of functional groups that are present in the CNC's surface and the macromolecular chains of the PVA/CMC blend are exploited to improve the interfacial interactions between the CNC and the blend. Consequently, these eco-friendly structured bio-nanocomposites with superior properties are expected to be useful in food packaging applications.