Evaluation of advanced oxidation processes and adsorption for the treatment of 1,2,4-triazole containing semiconductor wastewater

Azoles are widely employed as copper corrosion inhibitors in the semiconductor industry but pose environmental concerns due to their poor biodegradability and toxicity toward nitrifying microorganisms. Their occurrence in effluents highlights the need for effective treatment strategies. Here, four advanced oxidation processes (AOPs) - Fenton, UV/Fenton, UV/H₂O₂, and UV/persulfate processes - were systematically evaluated for the degradation of 1,2,4-triazole (TZ), a representative azole, in both lab-prepared and actual semiconductor wastewater collected immediately downstream of chemical mechanical planarization (CMP) manufacturing processes. While all three UV-assisted processes achieved complete degradation of 0.72 mM TZ from lab-prepared wastewater within 30 min, the UV/persulfate process exhibited the fastest kinetics (pseudo-first-order rate constant of 0.38 min⁻¹). However, in this semiconductor wastewater with 0.33 mM TZ, the UV/Fenton process exhibited the fastest kinetics and the highest TOC removal rate, underscoring the strong influence of matrix constituents. Given the high volume of this semiconductor wastewater, the potential of implementing a pre-concentration step was evaluated. Adsorption studies revealed that Fe(II)-zeolite exhibited the highest affinity for TZ, though its overall capacity was too low for practical pre-concentration. These findings provide practical guidance for optimising oxidation-based treatment strategies specifically for azole-containing semiconductor wastewater.