Direct quantification of As(III)/As(V) in copper smelting wastewater via deep ultraviolet (DUV) absorption spectroscopy

Effective arsenic pollution control necessitates real-time arsenic compositional monitoring, a demand that conventional analytical techniques struggle to meet due to limitations in timeliness and economy. Herein, an innovative deep ultraviolet (DUV) spectroscopy method is proposed, enabling the direct speciation and quantification of high concentration arsenic in copper smelting wastewater. High fidelity DUV spectra were acquired via a specialized measurement system that eliminated oxygen and stray light interferences, wherein the specific arsenic-related features revealed the capability for inorganic As(III)/As(V) quantification. TD-DFT simulations elucidated the differentiated spectral signatures of As species via distinct electronic transition mechanisms. In addition, matrix interference mechanisms on arsenic quantification were studied, with sulfuric acid modulating arsenic protonation states, and Fe(III) alongside Cu(II) inducing linear DUV spectral superposition. Incorporating these mechanistic insights, an optimized partial least squares (PLS) model was developed for the proposed analytical method, ensuring effective quantitative analysis of the arsenic species. Compared with conventional analytical techniques, the developed method achieved competitive accuracy across simulated and authentic wastewater samples with arsenic concentrations exceeding 0.1 M, while demonstrating significantly better green analytical chemistry scores. This approach realizes direct arsenic speciation and quantification without complex pretreatments, providing a rapid, economical, and sustainable analytical tool for arsenic pollution control. Furthermore, it offers a novel DUV analytical paradigm for monitoring highly concentrated and complex aqueous solutions across a broad range of process industries.