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 315.5 nm and 437.4 nm, respectively, both with low polydispersity. The influence on smaller particle size was defined by a low concentration of chitosan solution (0.2 mg/mL) and a higher dosage of TPP (1 mg/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 0.01 g and a contact time of 5 min, 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.