Treatment method for indigo-containing wastewater by combined adsorption and regeneration process

A method of treating indigo-containing wastewater to remove indigo from said wastewater, comprising:

• providing a column filled with an adsorbent capable of adsorbing the indigo;
• pumping the wastewater comprising the indigo into the column, thereby exposing the wastewater to the adsorbent for a sufficient period of time for the indigo to be adsorbed and generating indigo-saturated adsorbent and a column effluent;
• destroying residual gaseous ozone from the effluent:
• stopping the pumping of the wastewater into the column;
• and
• regenerating the indigo-saturated adsorbent by:
• (a) generating ozone in water with an ozone generator,
• (b) generating micro-nano-bubbles (MNBs) with a micro-nanobubbler in the water,
• (c) mixing the ozone and the MNBs in the water, and
• (d) directing the ozone mixed with the MNBs into the column, thereby decomposing the indigo;
• wherein the adsorbent is Fe(NO3)3 created by an impregnation-calcination procedure with Al2O3, and
• wherein no sludge comprising metal ions is generated upon completion of the method.