The invention relates to a
pollution-free production technology of direct fast black G, comprising the following implementation steps: firstly, primary acid
coupling is carried out on
nitroaniline after diazotization and H-acid; after the full reaction of the H-acid is detected,
sodium carbonate is added and pH is adjusted to 8 to 8.2 to carry out secondary basic
coupling; the
coupling product is added into a
sodium sulfide solution for reduction, and the temperature gradually raises to t of 38 DEG C to 40 DEG C in the reaction process; after the
sodium carbonate is added into the reduction product after acidification to adjust the pH of a medium to 7.5 to 8, the mixture is adsorbed by
activated carbon and filtered, and ternary coupling is carried out on the obtained filter liquor after diazotization and lentine; and after the reaction is detected to be end point, the materials are directly delivered to a
drying tower for
spray drying. In the invention, the reduced reaction solution does not need the processes of
salting out, acidification and
filtration,
activated carbon adsorption is adopted instead. In the process, no waste liquor is generated, and environment
pollution caused in the production process of dye is greatly reduced. Simultaneously,
wastewater processing is not needed, and the cost is saved. The optimized technology directly transfers the reaction solution after ternary coupling into the
drying tower for
spray drying; and the yield and the coloring intensity of the dye are effectively increased, energy is saved, the consumption is reduced, and the effect is obvious.