Degradation of Reactive Red 120 dye by a heterogeneous Sono-Fenton process with goethite deposited onto silica and calcite sand

Abstract

The degradation of Reactive Red 120 dye (RR-120) in synthetic waters was studied. Two processes were considered: homogeneous sono-Fenton with iron(II) sulfate and heterogeneous sono-Fenton with synthetic goethite and goethite deposited onto silica and calcite sand (modified catalysts GS and GC, respectively). In 60 min of reaction, the homogeneous sono-Fenton process allowed a degradation of 98.10 %, in contrast with 96.07 % for the heterogeneous sono-Fenton process with goethite at pH 3.0. The removal of RR-120 increased when the modified catalysts were used instead of bare goethite. Chemical oxygen demand (COD) and total organic carbon (TOC) measurements showed that the highest TOC and COD removals were achieved with the homogeneous sono-Fenton process. Biochemical oxygen demand (BOD5) measurements allowed confirmed that the highest value of BOD5/COD was achieved with a heterogeneous sono-Fenton process (0.88?0.04 with the modified catalyst GC), demonstrating that the biodegradability of the residual organic compounds was remarkably improved.