Synthesis of APS and simultaneous removal of heavy metals and organics from soil

Abstract

A commercially available alginic acid sodium salt (low viscosity, derived from Macrocystis pyrifera) was used for polymeric surfactant synthesis. Sodium alginate solution (3% w/v, 200ml H$_2$O+50ml 1-propanol) was mixed after adding periodate (30% oxidation degree of the uronic acid units, 1.908g) in the dark condition for 24hr at room temperature. The ethylene glycol (5ml) was added to decompose the unreacted periodate. At the last step, the reaction mixture was poured with stirring into ethanol (95%, 2l) and precipitate was collected by centrifugation, washed with ethanol, and dried. By controlling the amount of oxidant used, a various degree of product oxidized was obtained (10%-CHO~50%-CHO), and these five different 2,3-dialdehydic alginates, which were used as starting materials for synthesizing APSs. To a solution of 0.404g (about 2mmol) of 30% oxidized 2,3-dialdehydic alginate (30%-CHO) dissolved in 20ml of phosphate buffer pH 7 was added 0.092g of $NaCNBH_3$. The solution was mixed with 10ml of methanol containing C8-$NH_2$ (octyl amine), C12-$NH_2$ (dodecyl amine) or C16-NH2 (hexadecyl amine). The reaction molar ratio of alkyl amine to aldehyde on oxidized alginate was 5~7. The reductive amination was proceeded for 12hr with stirring at room temperature, and then the modified polymer was precipitated with two volumes of ethanol in the presence of NaCl (up to 10 g/l), centrifugated, successively washed with ethanol and dried. The final products of the above procedure were 30% CHO-C8, 30% CHO-C12, and 30% CHO-C16 APS. The synthesized 30% CHO-C12 APS formed colloidally stable self-aggregates (mean diameter of ca. 220nm) with a unimodal size distribution. The micelles of APSs have the properties such as surface activity and solubilization like monomeric micelles. In the case of 40% CHO-C8 APS, the lowest interfacial tension, 31.5 mN $m^{-1}$, was obtained at the CMC value of 1.35 g $L^{-1}$. From the basic tests of the chemically modified alginate, it was ...