Impact of pre-treatments on properties of lignocelluloses and their accessibility for a subsequent carboxymethylation

•Evaluation of different chemical and mechanical activation steps prior to carboxymethylation.•Milling increased the accessibility of lignocelluloses and enabled their carboxymethylation with high DSCM.•Chemical pre-treatments did not effectively enhance the subsequent carboxymethylation.•Carboxymethylation of lignocelluloses is promoted by the concomitant dissolution of matrix components. In this issue, different chemical (alkaline and sulfite pulping, ozonolysis) and mechanical (vibratory ball milling) pre-treatments were utilized for activating wheat straw and beech sawdust prior to carboxymethylation. Detailed analysis by a range of methods, including Klason-lignin, cellulose and hemicellulose quantification, Powder-X-ray diffraction (PXRD) and attenuated total reflection (ATR) IR spectroscopy, enabled the investigation of material alterations. Subsequently, carboxymethylation was carried out with both untreated and activated materials, allowing the evaluation of activation steps by determining degrees of substitution with carboxymethyl groups (DSCM). Moreover, carboxymethylation conditions were optimized, realizing high DSCM of up to 1.05. Results further revealed that ball milling enhanced the subsequent conversion; whereas chemical pre-treatments did not effectively increase material accessibilities. Further studies on chemically untreated materials emphasized that a highly reactive surface was already generated in the course of the carboxymethylation, inter alia through the concomitant dissolution of matrix components.