Preparation And Properties Of Polypyrrole-lignin Nanocomposites

Polypyrrole has a good comprehensive performance and a widely potential application as an adsorption material. However, the adsorption property of polypyrrole is proposed to be improved. To overcome this problem, three types of polypyrrole-based nanocomposites, were prepared with lignosulfonate (LS), enzymatic hydrolysis lignin (EHL) and chitosan (CS) as a dispersant, respectively.Firstly, polypyrrole-lignosulfonate (PPY-LS) and polypyrrole-enzymatic hydrolysis lignin (PPY-EHL) composite nanospheres were prepared facilely via an in-situ polymerization of pyrrole in the presence of LS and EHL as a dispersant, respectively. The as-prepared PPY-LS and PPY-EHL nanocomposites were characterized by SEM, IR, TGA, XRD. The results showed that the LS content had great effects on the size, structure and properties of the PPY-LS nanocomposites. Uniform PPY-LS nanocomposites with a mean diameter of 154 nm were achieved at a reaction temperature of 0 ℃ in ice-water bath for 24 h with the molar ratio of pyrrole to oxidant of 1:1 and a LS content of 10 wt.%; whereas PPY-EHL nanocomposites with a mean diameter of 50 nm were obtained under the same polymerization conditions. Furthermore, the adsorption performance of Ag+from aqueous solution onto the PPY-LS and PPY-EHL nanocomposites were studied. Batch experiments were conducted over a range of LS content, adsorption temperature, adsorption time, adsorbent dosage, initial pH value and initial Ag+concentration. Moreover, kinetics and thermodynamics of the adsorption process were also studied. The study showed that when the adsorption time was 72 h, the temperature was 25 ℃, the initial Ag+ concentration was 50 mg L-1, the adsorption capacity of PPY-LS and PPY-EHL nanocomposites was up to 1215.9 and 1337.8 mg g’1, respectively.The PPY-LS nanocomposites were also utilized to the adsorption of Pb2+ from aqueous solution. It was found that when the adsorption time was 8 h, the temperature was 25 ℃, the initial Pb2+ concentration was 200 mg L"1, the maximum adsorption capacity of the PPY-LS nanocomposite was up to 124.5 mg g-1.Secondly, polypyrrole-lignosulfonate-chitosan (PPY-LS-CS) composite nanobspheres were prepared via an in-situ polymerization of pyrrole in the presence of LS and CS as dispersants. The PPY-LS-CS nanocomposite were characterized by SEM, IR, TGA, XRD, and used to the adsorption of organic dyes from aqueous solution. Uniform PPY-LS-CS nanocomposites with a mean diameter of 73 nm were achieved at the reaction temperature of 0 ℃ in ice-water bath for 24 h with the molar ratio of pyrrole to oxidant of 1:1 when the CS and LS content was 10 wt.%, respectively. Batch experiments were conducted over six different organic dyes, adsorption temperature, adsorption time, adsorbent dosage, initial pH value and initial congo red concentration. Kinetics and thermodynamics of the adsorption were also studied. The study showed that when the adsorption time was 2 h, the temperature was 30 ℃, the initial concentration of the congo red was 60 mg L"1, the maximum adsorptivity of PPY-LS-CS nanocomposite for congo red was up to 99.3%. In additon, the absorption process of congo red on the PPY-LS-CS nanocomposite were a chemical spontaneous endothermic reaction.