Removal of iron?cyanide complexes from wastewaters by combined UV?ozone and modified zeolite treatment

SERGIO HANELA; JORGE DURÁN; JACOBO SILVIA

jurnal of environmental chemical engineering

Elsevier

Año: 2015 vol. 3 p. 1794 - 1801

A treatment system was developed to remove iron-complexed cyanide from wastewaters discharged bysmall surface finishing workshops. Alkaline chlorination, a widely used treatment method, does notremove iron?cyanide complexes and produces chlorine secondary pollution effects. In this work, theeffectiveness of a bench scale system with a UV?ozone step, followed by a fixed bed made of manganese-modified natural zeolite was studied to remove potassium hexacyanoferrate(II) K4[Fe(CN)6]. The systemwas operated on a semi-continuous basis processing up to 7.2 l batches of synthetic wastewater. Theoptimal residence time was established by feeding the system with a free iron solution and using aresidence time distribution (RTD) model.With the employed experimental conditions, a 66% cyanide removal was observed at the UV?ozonestage. The fixed bed retained 55% of the total iron fed and an additional 5% of iron was precipitated.Cyanide removal was slightly increased by fixed bed up to 68%. This method achieved a significantremoval of iron?cyanide complexes. The results were analysed by using an RTD model and a mechanismfor the processes occurred was proposed. Technical and economical scaling up conditions must bestudied in future works to assess the feasibility of treating wastewaters from small electroplating