Effect of the preparation method in the size of chitosan nanoparticles for the removal of allura red dye

Nanoparticles of chitosan-tripolyphosphate through two ionic gelation methods (Np1 and Np2) with different dosages of TPP and stirring time were prepared and characterized (FTIR, TEM, SEM-EDS, AFM, XRD, DLS and BET) for the removal of an allura red dye. Np1 and Np2 were obtained with a diameter size of 315.5nm and 437.4nm, respectively, both with low polydispersity. The influence on smaller particle size was defined by a low concentration of chitosan solution (0.2mg/mL) and a higher dosage of TPP (1mg/mL), while the stirring time did not affect the particle size. Dye removal was placed in batch mode by varying adsorbent dosage, time and pH. The removal percentage (R%) in Np1 decreased with an increase in adsorbent dosage at pH 4 and 6, while Np2 remained constant at pH 2, 4 and 6. Adsorption essays in Np1 and Np2 revealed that under pH 2, an adsorbent dosage of 0.01g and a contact time of 5min, the adsorptions are complete. Np2 was recognized as the best adsorbent in comparison with Np1 due to the highest R% under several pHs. This research has demonstrated that the obtained nanoparticles by ionic gelation are suitable for removal of azo dyes in water.