The chemical mechanism displayed in the sorption of heavy metal cations on barks was discussed through a modelling study of adsorption in relation to the nature of the ligand borne by the chemical components of the bark sorbent. The adsorption isotherms of five heavy metal cations (Cr3 +, Cu2 +, Ni2 +, Pb2 +, Zn2+) on five species of barks (Sweet chestnut, Oak, Douglas fir, Norway spruce, Scots pine species) were studied. The experimental data fitted well the Langmuir model, which allowed the expression of the mathematical parameters (qmax, maximum binding capacity; b, affinity). The qmax values increased conversely to the b values. The correlation of these mathematical values (qmax and b) with the analysis of the chemical composition of barks led us to note that Cu2 + interacts preferentially with phenolic groups present in lignins and tannins and, opposite in, Pb2 + with the carboxylic acid groups in polysaccharides. These observations were explained (i) quantitatively by the amount of different types of sites and (ii) qualitatively, by the physicochemical characteristics of cations, the nature and the tridimensional structure of adsorption sites. Finally, the results allowed to define the nature of the chemical interaction (monodentate or multidentate complex) between each specified chemical component of barks and each kind of heavy metal cations.
New crosslinked microcrystalline cellulose plastic films were made by olefin metathesis. Cellulose was first acylated under microwave irradiation by 10‐undecenoyl chloride in lithium chloride/N,N‐dimethylacetamide homogeneous solution to yield unsaturated fatty acid cellulose esters with a degree of substitution (DS) varying from 1 to 2. After studying the variation of cellulose DS vs. microwave irradiation time, the unsaturated fatty acid cellulose esters were subjected to olefin metathesis using Grubbs's catalyst. Crosslinking ratio T (0% < T < 90%) and gel formation during cross metathesis of cellulose esters with different DS are discussed. Structure elucidation was mainly achieved from IR and 1H NMR spectroscopic data.
Abstract Under mild conditions, treatment of unprotected methyl-α-D-glucopyranoside, N-acetylglucosamine and maltose with triphenylphosphine, diethylazodicarboxylate and equimolar amount of various carboxylic acids allowed regioselective 6-O-esterifications (6′-O for maltose) of the carbohydrate without esterification of other hydroxyl groups. This reaction found an application in the synthesis of liposoluble, labelled sugars and hydrosoluble polymers.
