Application of nano zero-valent iron particles coated by carboxymethyl cellulose for removal of Congo red dye in aqueous solution

Applying nanotechnology, particularly nano zero-valent iron encapsulated by carboxymethyl cellulose (CMC-nZVI), is considered less expensive and provides high efficiency for the decolorization of textile wastewater. In this study, Congo red dye (CR) was used in synthesized wastewater to evaluate the treatment performance using different composition ratios of CMC-nZVI. At the initial CR concentration of 500 mg/L, decolorization efficiencies increased with the increase of CMC contents. The removal efficiencies reached almost completely at the CMC:Fe2+ ratio of 0.004 within 10 seconds after adding CMC-nZVI to the CR solution. The optimal decolorization rate was observed at the Fe concentration of 1 g/L, with the CR removal efficiency of approximately 90% and a removal capacity of 8.298 g CR/g nZVI. The core principle of dye decolorization is breaking down the chromophore groups (-NN-), which makes the color of the dye, into N–H bonds. CMC-nZVI is a promising key to solving the issues caused by dye-containing wastewater.