Exploring Textile Effluent treatment Techniques to make Water drinkable

The Indian textile industry plays a vital role in the supply chain and marketing of garments and diverse handloom products, thereby strengthening India's commercial position in the global market. The exceptional performance of textiles in the regions of Gujarat, Tamil Nadu, Maharashtra, Rajasthan, Madhya Pradesh, and Punjab in terms of woollen production facilities. According to the Annual Survey of Industries (ASI), 23.6% of the textile sector in Gujarat exhibits high levels of production. 

 

 

Textile industries generate a large volume of complex effluents during the processing of clothes, and before discharging, which is a high organic and inorganic effluent load on the environment. Azo, Benzo, Cationic, Xanthene, a group of dyes that are effective in our humanity and the abiotic life cycle. According to the Central Pollution Control Board (CPCB) survey, 92 million tons of effluent were generated in FY23-24. This wastewater often shows high TDS, salinity, alkalinity, and electrical conductivity, primarily originating from salt-intensive dyeing processes. Additionally, textile wastewater contains heavy metals (Cr, Cu, Ni, Zn), formaldehyde-based resins, and chlorinated compounds, posing ecotoxicological and human health risks. Some of the most carcinogenic groups of dyes are the reactive dyes, which are harmful and highly soluble in water molecules, for example, RB21 (Reactive Turquoise Blue 21) dye. The general molecule's formula is C₄₀H₂₅CuN₉O₁₄S₅, represents a copper phthalocyanine reactive dye with multiple functional groups (nitrogen heterocycles, sulfonic groups) around a central Cu atom. Typically contains reactive vinyl sulfonyl (–SO₂–CH=CH₂) or sulfatoethylsulphonyl groups that can form covalent bonds with hydroxyl (–OH) groups of cellulose fibres during the dying process. One of the most advanced research studies was successfully published in a reputed journal, which one is the advance solutions to degrade this carcinogenic pollutant by using the AOPs (Advance Oxidation Processes) technique. 

Catalyst is the altering the rate of the reaction. One of the most susceptible, highly active, emerging, and advanced materials in the presence of visible light also enhances COD, BOD, and DO rates to make water drinkable. Recent breakthroughs to mineralise faster RB21 with the combination of materials with hybrid techniques like Photocatalyst+Ultrasonication, UV+Ozonation,  Corona Discharge Plasma with Fe2+ addition,n etc. 

    

Method	Approx. RB21 Removal	Notes
Corona plasma + Fe²⁺	~100% color removed, ~83 % COD ↓	Advanced oxidation
Photo‑ozonation	~99 %	Very short reaction times
SmFeO₃‑rGO + ultrasound	High degradation (faster)	Effective on the actual effluent
Fly ash adsorption	Moderate capacity (~105 mg g⁻¹)	Very low cost
Photocatalysis with MgFe2O4	93 %  removal rate	AOP, low cost

Figure 1: Advance Oxidation Process (AOPs) Techniques performance over RB21 dye degradation (Predictive analysis) (a) Various AOPs Utilised for RB21 dye (b) Concentration variation over RB21 with Vis. + H2O2

Figure 1 assumes a RB21 dye concentration of 25 ppm, utilising AOPs techniques, including ozonation, photocatalysis, photo-Fenton, and UV and Vis light irradiation with H₂O₂ as an oxidant to break the interaction between the dye and H₂O molecules. 

Azo bond is extremely ozone-sensitive -N=N- bond undergoes rapid cleavage, R-N=N-R + Ozone to form aromatic amines with smaller fragments. When using ozonation, one ozone molecule can break chromophoric structure, leading to rapid decolourisation, but at high concentrations of RB21,

Ozone ​+ OH− → •OH + O2​

$$•OH + \text{RB21} \rightarrow \text{fragmented intermediates}$$

$$\text{Why its happening, ozonation destroys chromophores first, and some aromatic fragments remain due to not destroyed completely, like sulfonated benzene/naphthalene derivatives. It becomes colourless but lack of degradation onto benzene rings. Why aromatic fragments are hard to remove becausethey have resonance stability and can react with ozone slowly in the presence of hydroxyl radicals. }$$