Interpretation of adsorption behaviour of cellulose, sodium carboxymethylcellulose and hydroxyethylcellulose onto activated kaolin

Cellulose and its derivatives (CDs) have been extensively used in various fields due to their valuable and remarkable chemical and physical properties. The applications of CDs have widely been recognized in various industries like textile & dyeing, papermaking, food, pharmaceutical, etc. However, there was a lack of understanding of the interaction mechanism between the CDs and solid surfaces which has hindered their possible applications, hence, adsorption of CDs onto solid surfaces has been a topic of long-standing debate. Several binding mechanisms have been developed, but as yet no common mechanism has received for general acceptance. Thus, the associated problem has received adequate attention. Therefore, systematic investigation employing in-depth characterizations of cellulose and its derivatives namely cellulose (CL), sodium carboxymethylcellulose (Na-CMC) and hydroxyethylcellulose (HEC) was chosen as a representative selection of polysaccharides for the study of their binding mechanism onto a solid surface (activated kaolin) to enhance the understanding of the binding mechanism. A batch mode adsorption experiment in the presence of various factors (concentration, adsorbent dose, pH, contact time and temperature) was investigated. The specific surface area of activated kaolin (AK) was SBET ​= ​18.57 ​m2/g. The AK exhibited pore distribution with a maximum peak centred at 10.534 ​nm and pore diameter ​= ​2.113 ​nm which indicates mesoporous nature. The zeta potential of AK was found to be 92.44(mV) suggested that it has strong stability and positive surface in an aqueous medium. The IR spectrum shifting has occurred in Si–O–H stretching at bands 1114 cm-1 and 694 ​cm-1 that may be attributed to the formation of hydrogen bonds between Si–O–H of activated kaolin and carboxylate ion of Na-CMC, hydroxyl ion of CL and HEC. Experimental data were best computed to the Langmuir, Freundlich, Halsey and Elovich, isotherm models with an adjusted determination coefficient (Adj. R2) which gave high correlation values as 0.99440, 0.96151, 0.96151 and 0.95295 respectively. Thus, the exploration of adsorption behaviour of titled polymers onto AK provides substantial evidence to prove that adsorption mainly occurs via hydrogen bonding followed by some electronic interactions and such adsorption aspect could play a noteworthy role in industrial applications.