Calcium alginate aerogels doped with polypyrrole/titanium dioxide nanoparticles for photodegradation of congo red dye.

Generally, semiconductor photocatalyst can only absorbed ultraviolet light and easily reunited in the using process, which affected their catalytic efficiency. In this work, the calcium alginate/polypyrrole/titanium dioxide (CA/PPy/TiO2) aerogel was prepared to photodegrade Congo red (CR) dye. The sensitization of TiO2 with PPy enabled energy absorption in visible light. The X-ray photoelectron spectrum (XPS) result confirmed hydrogen bonds between PPy and TiO2 proving tight combination between them. Ultraviolet-visible diffuse reflectance spectrum verified optical band gap narrowing of PPy/TiO2 in contrast to TiO2. When CA aerogel loaded with 0.6 g PPy/TiO2 nanoparticles, catalytic activity was the highest. The total degradation rate reached 81.1 % for a 30 mg/L CR solution at pH = 3. The degradation rate of CA/PPy/TiO2 was more than twice that of CA/TiO2. CA/PPy/TiO2 aerogel can immerse in water for a long time and keep structural integrity due to good swelling resistance, which surpassed most bio-based aerogels. This aerogel can effectively remove organic contaminants using just visible light and had high stability under strong acid and alkali conditions, which was appropriate for most water pollution control. This method of combining aerogel with photocatalyst might open up a new window for wastewater treatment.