Preparation and performance of a cellulose-based cationic flocculant CMC-PDMC for oily-sludge treatment

In the processing of oily sludge, conditioning the sludge by adding highly efficient and suitable flocculants is the key to successful treatment. This study employed sodium carboxymethyl cellulose (CMC), methacryloxyethyl trimethyl ammonium chloride (DMC), potassium persulfate (KPS), ammonium cerium nitrate (CAN), azobisisobutyronitrile hydrochloride (AAPH) as raw materials. Sodium carboxymethyl cellulose was graft-modified with methacryloxyethyl trimethyl ammonium chloride to prepare the cationic cellulose flocculant CMC-PDMC. Taking the de-oiling rate of oily sludge as the evaluation index, the effects of monomer mass ratio w(DMC):w(CMC), initiator type, reaction temperature and reaction time on the de-oiling rate were investigated via single-factor experiments. On the basis of the single-factor experimental results, orthogonal experiments were adopted to determine the optimal preparation process conditions, which are as follows: w(DMC):w(CMC) = 2:1, the initiator is AAPH, the reaction temperature is 75°C, and the reaction time is 2 hours. When applied to oil-contaminated sludge treatment at optimal conditions (dosage 70 mg/L, temperature 65°C, pH 9), this flocculant achieved an de-oiling rates of 84.69%, demonstrating excellent flocculation and separation performance. The mechanism of flocculants in treating oily sludge involves compressing the double electric layer, achieving electrostatic neutralization, forming bridging structures, and trapping and entrapment effects.