Boron Adsorption Kinetics of Microcrystalline Cellulose and Polymer Resin

Abstract

Tailoring boron−polysaccharide interactions is an important strategy for developing functional soft materials such as hydrogels, fire retardants, and sorbents for environmental remediation, for example, using lignocellulosic biomass. For such applications to be realized, it is paramount to understand the adsorption kinetics of borate anions on cellulose and their local structures. Here, the kinetic aspects of boron adsorption by microcrystalline cellulose, lignin, and polymeric resin are investigated and compared. Borate anions interact with the vicinal diols in the glucopyranoside moieties of cellulose to yield chemisorbed boron chelate complexes. In contrast to cellulose, technical lignin contains fewer cis-vicinal diols, and it does not have a tendency to form such chelate complexes upon treatment with the aqueous boric acid solution. The formation kinetics and stability of these chelate complexes strongly depend on nanoscale structures, as well as reaction conditions such as pH and concentration of the sorbate and sorbent. Specifically, insights into the distinct boron adsorption sites were obtained by solid-state one-dimensional (1D) 11 B magic-angle spinning NMR and the local structures and intermolecular interactions in the vicinities of boron chelate complexes are elucidated by analyzing two-dimensional (2D) 1 H− 13 C and 11 B− 1 H heteronuclear correlation NMR spectra. The total boron adsorption capacity of cellulose is estimated to be in the 1.3−3.0 mg range per gram of sorbent, which is lower than the boron adsorption capacity of a polystyrene-based resin, ∼17.2 mg of boron per gram of Amberlite IRA 743. Our study demonstrates that the local backbone and side chain flexibility as well as the structures of polyol groups play a significant role in determining the kinetic and thermodynamic stability of chelate complexes, yielding to different boron adsorption capabilities of lignocellulosic polymers.

Crosslinking of Epoxidized Natural Rubber with Borax for Self‐Healing and Self‐Repairing Properties: pH Dependence

“…This facilitated the formation of the complex with diol groups of ENR. [ 26–28 ] However, when the borax loading increased, the L–B–L/L–B ratio decreased. This decrease might be caused by an excessive amount of B(OH) 4 − (excess borax) and an increase in L–B formation, as suggested by an increase in %area of the peak at 0 ppm.…”

“…The formation of the L–B complex is more favored than the formation of L–B–L complex because the latter requires two diol units on adjacent chains, which is more challenging in terms of steric requirements than the former. [ 28 ]…”

“…A previous study reported that the L–B complexes may undergo exchange reactions, and washing may partially remove these complexes. [ 28 ] Therefore, the removal of excessive borax [L–B complexes, unreacted B(OH) 3 , and B(OH) 4 − ] may occur, particular in the case of 11B30, after washing the ENR. Moreover, a decrease in the content of these boron complexes resulted in a porous structure, allowing the solvent to easily penetrate and dissolve the rubber chains.…”

Preparation and Selective Adsorption Performance of the Carboxymethyl Salix psammophila Wood Powder-Imprinted Membrane for Tetracycline

“…Adsorption kinetics is used to analyze the relationship between the adsorption rate and adsorption dynamic equilibrium. In order to further understand the adsorption mechanism of TC on CMSM-MIPs (CMSM-NIPs), a pseudo-first-order kinetic model 19 and a pseudosecond-order kinetic model 20 were used to fit and analyze the experimental data.…”