Application of dye saturated clay adsorbent from dyeing wastewater as textile printing pigment
Abd Allah Rahimi, Farzaneh Alihosseini
Abstract
Abstract Background Adsorption by cheap materials (like clay and activated carbon) is one of the most effective methods for treating dye wastewaters, especially for cationic dyes. Although activated carbon has a black residue, the unique nanostructure of clay adsorbs dye molecules between its layers and produces a colored sludge. Dye intercalated clays were also introduced as possible coloring pigments. This work tries to combine the wastewater treatment and hybrid pigment production processes so that the remaining sludge of the process can be used as a printing pigment. Results Bentonite clay was examined for treating real dye wastewater from the textile industry containing four cationic dyes. The adsorption mechanism of all dyes was studied individually, and the results show that bentonite has a minimum adsorption capacity of 467 mg/g for Basic Red 46 dye based on the Langmuir model. The adsorption process decreased the turbidity by about 86% and reduced the total dissolved solids (TDS) and chemical oxygen demand (COD) of wastewater. The produced hybrid showed a nano‐layer structure according to the field emission scanning electron microscopy (FESEM). Differential thermal analysis (DTA) shows that the thermal stability of the pigment improved by about 30 °C compared to the pristine dye. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) showed that the dye: bentonite ratio should be adjusted at a medium level to control the hydrophilicity of the hybrid and improve its miscibility in binders. Conclusion The produced pigment was printed on cotton fabric with a desirable visual color appearance and showed acceptable rubbing and light fastnesses. The result indicates that wastewater sludge from this adsorption process could be applicable as an industrial pigment. © 2022 Society of Chemical Industry (SCI).