Oxidation of cyanide in aqueous solution by ozonisation in the presence of modified activated carbon

[EN] The aim of this study was to analyze the role of activated carbon on cyanide ozonation in aqueous phase. The results show that activated carbon previously treated with ammonia had a marked effect on the kinetics of cyanide removal. According to the results obtained by FTIR and XPS techniques, ammonia treatment increase the superficial concentration of carbonyl groups, which in the interaction with ozone could potentiate the generation of highly oxidizing radicals on the medium, justifying the results obtained.[ES] El objetivo de este trabajo fue analizar el papel que desempeña el carbón activado en el proceso de ozonización del anión cianuro. Los resultados obtenidos muestran que el carbón activado previamente tratado con amoniaco incrementó considerablemente la velocidad de eliminación del anión cianuro. Los resultados obtenidos mediante FTIR y XPS muestran un incremento en la concentración de grupos carbonilo, los cuales con la interacción con el ozono podrían potenciar la generación de radicales altamente oxidantes en el medio justificándose así los resultados obtenidos.Agradezco el apoyo al Consejo Nacional de Ciencia y Tecnología (CONACYT) por la beca otorgada 176351 para cursar el Doctorado en Ciencia y Tecnología de los Materiales dentro del programa de Doctorado de la Universidad Autónoma de Coahuila en la Facultad de Ciencias Químicas de Saltillo, Coahuila, MéxicoPeer reviewe

Use of Thermally Modified Jarosite for the Removal of Hexavalent Chromium by Adsorption

Jarosites are residues generated during the purification of zinc and are composed mainly of iron sulfates ((Na, K)Fe3(SO4)2(OH)6). Due to the large volume of jarosite generated during the process, these residues tend to be deposited in large land areas and are not used. In the present work, jarosite was used without heat treatment (JST) as an adsorbent of hexavalent chromium contained in a sample of wastewater from a chrome plating industry under the following conditions: C0 = 200 mg/L of Cr, T = 25 °C, and pH = 3. It was only possible to remove 34% of Cr (VI). Subsequently, a thermal treatment of a jarosite sample (JTT) was carried out at 600 °C. The heat-treated sample was later used as an adsorbent in the same conditions as those for JST. The maximum chromium removal was 53%, and the adsorption capacity was 10.99 mg/g. The experimental data were fitted to the Langmuir model and to the pseudo-second-order kinetic model. It was determined that the adsorption process involved electrostatic attractions between the surface of the positively charged adsorbent and the chromium anions contained in industrial wastewater