In the presence of pyridine as a catalyst

a bio-based surfactant was synthesized via the alkylation of sodium lignosulfonate (LS) with 1-bromododecane in an alkalic isopropanol/water solution

with the aid of ultrasonic treatment.Structure and property characterization of sodium lignosulfonate (LS)

alkylated sodium lignosulfonate without ultrasonication (ALS) and alkylated sodium lignosulfonate with ultrasonication (UALS) were performed by GPC

UV

FTIR and 1H-NMR.The results showed that molecular weight of sodium lignosulfonate decreased from 154200 to 106000 after ultrasonic treatment while the phenolic content of sodium lignosulfonate increased from 0.65% to 1.55%.And the content of methoxy reduced from 36.0% to 21.0% at the same time.The results also showed that the alkylation of sodium lignosulfonate with the aid of ultrasonic treatment was more effective than that of without ultrasonic treatment.The alkylation of sodium lignosulfonate primarily occurred in phenol sites.As a result of the improvement of alkylation

surface activity analysis showed that surface tension of 1% aqueous solution of UALS decreased to 28.2 mN/m

by contrast to 34.1 mN/m of ALS and 41.5 mN/m of LS at the identical concentrations.Crucial micelle concentration of UALS was 510-2g/L

two orders lower than that of LS.Because hydrophobic group was effectively grafted to the macromolecule of sodium lignosulfonate under the influence of ultrasonication

UALS could hold a well-ordered molecular arrangement on the interface between the water and the air.Thus

it showed better surface activity than LS and ALS.And there were two possibly main reasons accounting for the enhancement of alkylating results with the assistance of ultrasonic treatment:on the one hand

it was ascribed to the generation of phenolic groups

and on the other hand

it was attributed to the cleavage of complicated molecular structures of sodium lignosulfonate under the influence of ultrasonication.