The introduction of phosphate groups into cellulosic fibers allows for the tuning of their fire resistance, chelating and metal-adhesion properties, enabling the development of flame-retardant adhesive and adsorbent materials. Toward that end, the major challenge is developing a novel efficient and environmentally friendly phosphorylation route that offers an alternative to existing methods, which can achieve the targeted properties. For this purpose, cellulosic fibers were chemically modified herein using solid-state phosphorylation with phosphoric acid and urea without causing substantial damage to the fibers. The morphological, physicochemical, structural and thermal characterisations were examined using FQA, SEM, EDX, FTIR, ¹³C/³¹P NMR, conductometric titration, zeta potential measurement and thermogravimetric analysis. All the characterisations converge towards a crosslinked polyanion structure, with about 20 wt% grafted phosphates, a nitrogen content of about 5 wt% and a very high charge density of 6608 mmol kg⁻¹. Phosphate groups are linked to cellulose through a P–O–C bond in the form of orthophosphate and pyrophosphates. Furthermore, thermal properties of the phosphorylated cellulosic fibers were investigated and a new degradation mechanism was proposed.

Heavy metal toxicity has demonstrated to be a crucial issue for environment and human health. There has been an increasing ecological and global public health concern related with environmental contamination by these metals. For these reasons, a considerable attention has been paid to design efficient materials for heavy metal removal. This article offers a solution to develop a green adsorbent based on Chitosan Microspheres/Sodium Alginate hybrid beads (CSM/SA) for metal ion elimination from aqueous solutions. The efficiency of this eco-friendly material was divulged using kinetic study for Cr(VI) and Pb(II) removal. Properties of the obtained hybrid beads were improved by correlation between original chitosan microspheres and sodium alginate. Moreover, at different metal concentration, pH solution and contact time, the beads were evaluated in discharged batch operations from Pb(II) and Cr(VI). The maximum adsorption capacity was 180 mg g^− 1 for Pb(II) and 16 mg g^− 1 for Cr(VI). The adsorption kinetics were evaluated using pseudo-first and pseudo-second rate models. Adsorption isotherms were simulated by Langmuir and Freundlich models. This study indicates that the CSM/SA hybrid beads could be developed into a very sustainable technology for highly effective elimination of metal ions from wastewater.

A novel sustainable hydrogel catalyst based on the reaction of sodium alginate naturally extracted from brown algae Laminaria digitata residue with copper(II) was prepared as spherical beads, namely Cu(II)-alginate hydrogel (Cu(II)-AHG). The morphology and structural characteristics of these beads were elucidated by different techniques such as SEM, EDX, BET, FTIR and TGA analysis. Cu(II)-AHG and its dried form, namely Cu(II)-alginate (Cu(II)-AD), are relatively uniform with an average pore ranging from 200 nm to more than 20 μm. These superporous structure beads were employed for the copper catalyzed [3 + 2] cycloaddition reaction of aryl azides and terminal aryl alkynes (CuAAC) via click chemistry at low catalyst loading, using water as a solvent at room temperature and pressure. The catalytic active copper(I) species was generated by the reduction of copper(II) by terminal alkyne via the oxidative alkyne homocoupling reaction. The prepared catalysts were found to be efficient (85–92%) and regioselective by affording only 1,4-disubstituted-1,2,3-triazoles. They were also recoverable and reused in their dried form for at least four consecutive times without a clear loss of efficiency. A mechanistic study was performed through density functional theory (DFT) calculations in order to explain the regioselectivity outcome of Cu(II)-alginate in CuAAC reactions. The analysis of the local electrophilicity (ω_k) at the electrophilic reagent and the local nucleophilicity (N_k) at the nucleophilic confirms the polar character of CuAAC. This catalyst has the main advantage of being sustainably ligand-free and recyclable.