Production of modified carboxymethyl cellulose from sawdust and wheat straw

Abstract

Mines in Zimbabwe are facing a challenge in acquiring modified carboxymethyl cellulose with enhanced depressive properties in flotation pulps because at the moment it is not being produced in the country and this triggered the research on the production of the in demand flotation depressant from wheat straw and sawdust. This involved the extraction of cellulose from wheat straw and sawdust and then modification of the cellulose to carboxymethyl cellulose. A 31.04 % yield of cellulose was successfully extracted from wheat straw and 49.28% from sawdust through alkali treatment process. The cellulose was then converted to Carboxymethyl Cellulose (CMC) by mercerization with various sodium hydroxide (NaOH) concentrations and subsequently etherified with monochloroacetic acid. The CMC yield of cellulose samples from wheat straw and sawdust were 76.80% and 76.40% respectively. The absolute degree of substitution (DSabs) of CMC was found to increase with increasing concentrations of NaOH up to 30% (w/v) of NaOH and decreased at higher NaOH concentration. The molecular weight was determined using intrinsic viscosity and was found to have the same trend as DSabs. Higher DSabs provide a stronger inter-molecular interaction between carboxymethyl and hydroxyl groups which result in higher mechanical properties.