Phosphorylated chitin from shrimp shell waste: A robust solution for cadmium remediation.

In this work, chitin (CT) was isolated from shrimp shell waste (SSW) and was then phosphorylated using diammonium hydrogen phosphate (DAP) as a phosphorylating agent in the presence of urea. The prepared samples were characterized using Scanning Electron Microscopy (SEM) and EDX-element mapping, Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA/DTG), conductometric titration, Degree of Substitution (DS) and contact angle measurements. The results of characterization techniques reveal the successful extraction and phosphorylation of chitin. The charge content of the phosphorylated chitin (P-CT) was 1.510 mmol·kg-1, the degree of substitution of phosphorus groups grafted on the CT surface achieved the value of 0.33. The adsorption mechanisms appeared to involve electrostatic attachment, specific adsorption (CdO or hydroxyl binding), and ion exchange. Regarding the adsorption of Cd2+, the effect of the adsorbent mass, initial concentration of Cd2+, contact time, pH, and temperature were studied in batch experiments, and optimum values for each parameter were identified. The experimental results revealed that P-CT enhanced the Cd2+ removal capacity by 17.5 %. The kinetic analyses favored the pseudo-second-order model over the pseudo-first-order model for describing the adsorption process accurately. Langmuir model aptly represented the adsorption isotherms, suggesting unimolecular layer adsorption with a maximum capacity of 62.71 mg·g-1 under optimal conditions of 30 °C, 120 min, pH 8, and a P-CT dose of 3 g·L-1. Regeneration experiments evidenced that P-CT can be used for 6 cycles without significant removal capacity loss. Consequently, P-CT presents an efficient and cost-effective potential biosorbent for Cd2+ removal in wastewater treatment applications.

Bio-based functionalized adsorptive polymers for sustainable water decontamination: A systematic review of challenges and real-world implementation.

The overwhelming concerns of water pollution, industrial discharges and environmental deterioration by various organic and inorganic substances, including dyes, heavy metals, pesticides, pharmaceuticals, and detergents, intrinsically drive the search for urgent and efficacious decontamination techniques. This review illustrates the various approaches to remediation, their fundamentals, characteristics and demerits. In this manner, the advantageous implementation of nature-based adsorbents has been outlined and discussed. Different types of lignocellulosic compounds (cellulose, lignin, chitin, chitosan, starch) have been introduced, and the most used biopolymeric materials in bioremediation have been highlighted; their merits, synthesis methods, properties and performances in aqueous medium decontamination have been described. The literature assessment reveals the genuine interest and dependence of academic and industrial fields to valorize biopolymers in the adsorption of various hazardous substances. Yet, the full potential of this approach is still confined by certain constraints, such as the lack of reliable, substantial, and efficient extraction of biopolymers, as well as their modest and inconsistent physicochemical properties. The futuristic reliance on such biomaterials in all fields, rather than adsorption, is inherently reliable on in-depth investigations and understanding of their features and mechanisms, which can guarantee a real-world application and green technologies.

Investigating the effect of clay content and type on the mechanical performance of calcium alginate-based hybrid bio-capsules.

This study aims to investigate the mechanical behavior of alginate-based simple and alginate@clay-based hybrid capsules under uniaxial compression using a Brookfield force machine. The effect of clay type and content on Young's modulus and nominal rupture stress of the capsules was investigated and characterized using Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (ATR-FTIR). Results showed that clay content improves the mechanical properties depending on its type. Montmorillonite and laponite clays showed optimal results at 3 wt% content, with a gain of 63.2 % and 70.34 % on Young's modulus, and a gain of 92.43 % and 108.66 % on nominal rupture stress, respectively, while kaolinite clay showed optimal results at 1.5 wt% content with an increase of 77.21 % on Young's modulus and 88.34 % on nominal rupture stress. However, exceeding the optimal content led to decrease the elasticity and rigidity due to the incomplete dispersion of clay particles in the hydrogel network. The theoretical modeling using Boltzmann superposition principle revealed that the elastic modulus was in good agreement with experimental values. Overall, this research provides insights into the mechanical behavior of alginate@clay-based capsules, which could have potential applications in drug delivery systems and tissue engineering.

Effects of direct sulfonation on the catalytic activity and recyclability of novel lignin-based solid acid catalysts from agri-food waste.

Catalytic systems derived from lignin are emerging as quite efficient and profitable materials in many catalyzed transformations. However, these catalysts have been predominantly synthesized by carbonization. Alternatively, we prepared direct sulfonation lignin (DSL) and compared it to the carbonized-sulfonated lignin (CSL) catalyst, aiming to reveal the effects of direct functionalization of lignin on its catalytic performance and to simplify its preparation. Both catalysts were well characterized by several physicochemical techniques, and their catalytic activities were assessed by catalyzed esterification. Using CSL, the yield reached 94.11 % under the optimal conditions (60 °C, 4 h and 50 mg loading), while DSL yielded 93.97 % with only 2 h under the same conditions, which is attributed to the abundant catalytic active sites in DSL (0.62 mmol/g of SO3H against 0.39 mmol/g for CSL). Furthermore, the activation energies were found to be 21 and 16 kJ mol-1 for CSL and DSL, respectively, suggesting that esterification can occur with less energy input using DSL. Reusability showed that leaching of SO3H groups and mass loss are inherently responsible for deactivation. However, both lignin-based catalysts show good stability and can be reused for 4 successive cycles. Direct lignin functionalization can be an alternative to conventional catalyst processing.

Insights on the physico-chemical properties of alkali lignins from different agro-industrial residues and their use in phenol-formaldehyde wood adhesive formulation.

The current study investigates for the first time the physico-chemical performances of lignins from cactus waste seeds (CWS) and spent coffee (SC) in comparison to previously isolated lignins from sugar byproducts (bagasse (SCB) and beet pulp (SBP)). In this work, lignin-phenol formaldehyde (LPF) resins were formulated using various lignin loadings (5-30 wt%), characterized and applied in the manufacturing of plywood panels. Several characterization techniques were applied to identify the chemical and morphological properties, thermal stability, and phenolic content of the extracted lignins, as well as the bonding strength and wood failure of the formulated resins. Results showed that the CWS and SC could be considered as an important source for lignin recovery with a considerable yield of 15.46 % and 27.08 % and an important hydroxyl phenolic content of 1.26 mmol/g and 1.36 mmol/g for CWS and SC, respectively. Interestingly, 20 wt% of extracted lignins in PF adhesives were the optimal formulation showing an improved modulus of elasticity (MOE) of about 3505, 3536 and 3515 N/mm2, and a higher modulus of rupture (MOR) of about 55, 55 and 56 N/mm2 for panels containing CWS, SC and SCB-lignins, respectively, over the reference panels (MOE = 3198 N/mm2 and MOR = 48 N/mm2). Additionally, formaldehyde emission from plywood remarkably decreases by up to 20 % when lignin was incorporated into the PF matrix. Herein, the treatment of the CWS and SC for the extraction of alkali lignin and its application showed a new route to produce high added-value products from underused residues.

Beneficiation of cactus fruit waste seeds for the production of cellulose nanostructures: Extraction and properties.

Cactus fruit waste seeds (CWS) are a by-product of the cactus fruit processing industry. Until now, CWS are not recoverable in any sector. The valorization of these residues may reduce their volume in the environment and transform them into valuable products. In this work, CWS have been identified for the first time as a sustainable lignocellulosic source. Cellulose microfibers (CMFs) and nanocrystals (CNCs) were successfully produced via alkali and bleaching treatments followed by sulfuric acid hydrolysis. It was found that the extracted CMFs showed an average diameter of 11 µm, crystallinity of 72%, and a yield of 25%. The as-produced CNCs exhibited a needle-like shape with a diameter of 13 ± 3 nm and length of 419 ± 48 nm, giving rise to an aspect ratio of 30.7, with a zeta potential value of - 30 mV and a charge content of sulfate groups of 287.8 mmol·kg-1. Herein, the obtained cellulosic derivatives with excellent properties from this underutilized waste can draw the attention of researchers towards CWS as a new type of biomass with virtually no hemicellulose, which could be of great interest to isolate and study the effects of how lignin interacts with cellulose.