Selective adsorption of Carboxymethyl cellulose at mesoporous powdered mustard cake

The mechanism of adsorption of carboxymethyl cellulose (CMC) onto solid-liquid interface has been a topic of long-standing debate. An attempt has, therefore, been made on adsorption aspects of CMC at the solid-liquid interface employing SEM, FTIR, XRD, BET, AFM and other techniques. The adsorption of the CMC onto mesoporous carbon (powdered activated mustard carbon, PAMC) derived from mustard cake was found to be affected significantly by change in solution conditions. Langmuir modeling of the adsorption isotherm suggests hydrogen bonding to be dominant force for polysaccharide adsorption as the adsorption free energy of CMC (~ -21.63 kJ/mol) was found close to that of hydrogen bond formation. The presence of urea reduced the adsorption of CMC on PAMC, significantly which supports that adsorption in the present case is attributed to the presence of hydrogen bonding. All of the above results suggest that the adsorption of CMC on the surface of PAMC is a complex interplay of electrostatic attraction and hydrogen bonding rather than hydrophobic force as reported in the literature. Thus, the present study provides substantial evidences to prove beyond doubt that adsorption of CMC on mesoporous carbon surface are predominant by electrostatic interaction and hydrogen bonding