Modified synthesis of nanoscale zero-valent iron and its ultrasound-assisted reactivity study on a reactive dye and textile industry effluents

Abstract

Synthesized nanoscale zero-valent iron (NZVI) particles were applied for the degradation of a reactive dye Remazol Black B 133 and textile effluent. XRD and HR-TEM analysis of the synthesized particles showed body centered cubic crystal packing. The aggregates were spherical in shape and the size of the particles ranged from 5 to 15 nm. The reactive dye solution was substantially degraded by NZVI particles using ultrasonic irradiation under various experimental conditions created by varying NZVI dosages (0.15–0.30 g/L), initial dye concentration (25–200 mg/L), and pH (2–13). Experimental results suggest that NZVI particles work best within the pH range of 4–10. A unit gram of NZVI was found to degrade a maximum of 749.2 mg of RB B 133 dye and more than 80% of the dye was removed within 15 min of reaction time. During the degradation process, an oxidation–reduction potential change from 196 to −577 mV was detected, indicating reductive condition is necessary for effective dye removal. FT-IR analysis of the end products of the degradation process indicated the presence of an amino (–NH2) group resulting from the breakdown of the azo (–N=N–) group. Results suggest that the degradation followed pseudo-first-order kinetics with respect to dye concentration. The effluents of two textile industries were collected, characterized, and treated with NZVI particles, which led to the significant fall below the standard scale of American Dye Manufacturing Institute (ADMI). This lowering of ADMI value indicates that the overall color removal efficiency is irrespective of any specific dye present in the effluent.