Efficient removal of safranin from aqueous solution using a new type of metalated highly self-doped polyaniline nanocomposite

Abstract We report the chemical synthesis of poly(aniline-co-aniline-2,5-disulfonic acid)) in a composite containing L-hexuronic acid and metallic Ag/SiO2 nanoparticles as a new anionic polyelectrolyte for removing safranin dye. The composite was characterized by IR, UV, cyclic voltammetry, SEM, TEM, TGA, DSC, EDXS and elemental analyses. Microscopic images of the metallic nanospheres exhibited well-separated spherical particles, while the targeted nanocomposite displayed intensified spherical particles that were dispersed over almost the entire surface. The XRD exhibited peaks of amorphous silica and crystalline silver at many 2q values, and their interatomic spacing values (d) and crystallite (grain) sizes were calculated. The thermal degradation curves exhibited interesting models of stability of copolymers and their weight losses left more than 50% as a residue. The cyclic voltammograms exhibited characteristic redox peaks relative to the quinoid ring transition states. Experimental parameters such as pH, adsorbent dose, contact time, and dye concentration were studied to evaluate the efficiency of copolymers as safranin adsorbents. The uptake rates up to 82.5% adsorption were completed within 75 min and the equilibrium time was 45 min. The adsorption maximum removal values were 73.6% and 59.3% at pH 9, while the maximum removal percentages were 55% and 68.3% attributed to overcrowding of adsorbent molecules that prohibit dye/adsorbent binding. From the Langmuir and Freundlich isotherm models used to interpret the dye/adsorbent interaction, the former isotherm was the optimum to represent the dye uptake. Different kinetic models to study adsorbent capacity through chemisorption and physisorption were also investigated.