Arsenazo III removal from diagnostic laboratories wastewater by effective adsorption onto thermochemically modified ordered mesoporous carbon

Abstract Arsenazo III removal from wastewater following Ca determination by mesoporous carbon was investigated. The CMK-3 carbon was synthesized by a hard-templating route with SBA-15 as the template and sucrose as carbon precursor. Obtained carbonaceous material was thermochemically modified with dicyandiamide at 900 °C. Dicyandiamide-modified CMK-3 was characterized by physicochemical methods. The adsorption efficacy of studied carbon towards arsenazo III dye was studied and compared to commercial activated carbon. The highest static adsorption capacity of arsenazo III dye (108 mg · g−1) on the studied mesoporous carbon was observed at pH 3 after 1 h. The experimental kinetics and equilibrium data were the best fitted to the Elovich and Langmuir-Freundlich theoretical models, respectively. Ca2+ had no effect on arsenazo III adsorption onto dicyandiamide-modified CMK-3. The arsenazo III dye was adsorbed onto studied modified mesoporous carbon by various mechanisms (electrostatic attraction, hydrogen bonding, π-π and van der Waals interactions). The desorption of arsenazo III from the dicyandiamide-modified carbon was not complete, even while using 1 mol · L−1 NaOH. The results showed that dicyandiamide-modified carbon can be successfully utilized for arsenazo III removal from laboratory wastewater after calcium determination in urine or blood serum.