Key Takeaways & Executive Findings
- •• • Achieves As(V) quantification in <10 min and total As (and As(III) by difference) in <15 min, enabling real-time process control and emergency response in industrial settings. • • Optimal conditions: H+ = 1 mol·L−1, Na2S = 5 mmol·L−1, reaction 3 min, N2 purge 2 min; for total As: NaClO = 10 mmol·L−1, oxidation 5 min at pH 12. These parameters ensure complete reaction and removal of H2S interference. • • Linear range 0.5–50 mg·L−1 (R² = 0.999), detection limit 0.17 mg·L−1, spike recoveries 101.9%–104.1%, RSD 1.06%, demonstrating high accuracy and precision for industrial wastewater matrices. • • Field validation against HPLC-ICP-MS and IC-HG-AFS on real mining wastewater showed relative deviations <10%, confirming reliability while cutting instrument cost and operational complexity dramatically.
Abstract
Arsenic is a toxic metalloid predominantly present in water as As(V) and As(III), whose speciation governs toxicity and mobility. Conventional speciation methods (HPLC-ICP-MS, IC-HG-AFS) offer ultralow detection limits but suffer from high cost, long analysis times, and non-portability, hindering on-site rapid monitoring. This study presents a sulfide-based spectrophotometric method exploiting the quantitative reaction between As(V) and S2− to form monothioarsenate (H3AsO3S) with a characteristic absorption at 233 nm. Under optimized conditions (H+ concentration 1 mol·L−1, Na2S dosage 5 mmol·L−1, reaction time 3 min, N2 purging 2 min), As(V) is directly quantified. Total arsenic is determined after complete oxidation of As(III) to As(V) using NaClO (10 mmol·L−1, pH 12, 5 min), and As(III) is obtained by difference. The method exhibits linearity over 0.5–50 mg·L−1 (A = 0.0209c + 0.0627, R² = 0.999), a detection limit of 0.17 mg·L−1, spike recoveries of 101.9%–104.1%, and relative standard deviation of 1.06%. Validation against real industrial wastewater samples showed relative deviations <10% compared with HPLC-ICP-MS and IC-HG-AFS. Total analysis time is within 15 min. The method is simple, cost-effective, and suitable for field monitoring.
1. Introduction
Industrial effluents from mining, metallurgy, and semiconductor fabrication discharge arsenic at rates exceeding 2.3×10^4 t annually, with As(III) being 60 times more toxic and 3–8 times more mobile than As(V). Regulatory compliance and remediation demand rapid speciation at the point of discharge, yet current laboratory-grade techniques—HPLC-ICP-MS and IC-HG-AFS—remain confined to centralized facilities due to prohibitive capital costs (millions of RMB), high-purity argon consumption, and specialized maintenance. Field-deployable alternatives such as the silver diethyldithiocarbamate method only quantify total arsenic, while the molybdenum blue method suffers from phosphate and silicate interference and requires meticulous control of zinc particle size and boiling water bath timing, rendering it error-prone under industrial conditions.
This work introduces a sulfide-based spectrophotometric assay that exploits the rapid, stoichiometric conversion of As(V) to monothioarsenate under strongly acidic conditions, yielding a distinct UV absorbance at 233 nm. By oxidizing As(III) to As(V) with sodium hypochlorite, total arsenic is determined, and As(III) is calculated by difference. The protocol eliminates the need for hydride generation, chromatographic separation, or high-temperature digestion, reducing analysis time to under 15 minutes while maintaining accuracy within 10% of reference methods. This approach directly addresses the operational bottleneck of on-site arsenic speciation, offering a cost-effective, portable solution for industrial wastewater monitoring and emergency response.
Loading authentic research manuscript (Pages 1–5)...
ZHOU Guotao, KONG Linghao, ZHAO Yanxia, WANG Enquan, PENG Xianjia (2026). Spectrophotometric Method for Rapid Determination of As(V) and As(III) in Industrial Wastewater. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202507030
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What are the potential interferences from common coexisting ions in industrial wastewater, and how does the method mitigate them?
The method's selectivity relies on the specific reaction between As(V) and sulfide under strongly acidic conditions (pH 0). Common anions such as phosphate and silicate do not form UV-absorbing thio complexes under these conditions, thus avoiding the false positives seen in molybdenum blue methods. Nitrogen purging for 2 min removes residual H2S, which would otherwise interfere. The study reports spike recoveries of 101.9%–104.1% in real wastewater matrices, indicating minimal matrix effects.
How does the method perform at arsenic concentrations below 0.5 mg/L, and what is the practical detection limit for field applications?
The linear range is 0.5–50 mg/L, with a detection limit of 0.17 mg/L. For concentrations below 0.5 mg/L, the method may require preconcentration or is not recommended. However, for many industrial effluents where arsenic levels exceed regulatory limits (often >0.5 mg/L), this range is adequate. The detection limit is sufficient for screening and emergency response, though not for trace-level environmental monitoring.
What is the cost per analysis compared to HPLC-ICP-MS, and what are the main consumables?
The method uses only common reagents (Na2S, NaClO, H2SO4) and a portable UV-Vis spectrophotometer. Consumable cost per sample is estimated at <$1, versus $50–100 for HPLC-ICP-MS including argon and column maintenance. The capital cost of a portable spectrophotometer is <$5,000, compared to >$200,000 for ICP-MS. This makes the method economically viable for routine on-site monitoring by small and medium enterprises.
How robust is the method to variations in sample matrix, such as high chloride or organic content?
The method was validated on real mining wastewater, showing relative deviations <10% against reference methods. High chloride concentrations may quench the UV signal, but the acidic conditions and nitrogen purging help mitigate. Organic matter that absorbs at 233 nm could interfere; however, the study did not report such cases. For complex matrices, a matrix-matched calibration or standard addition is recommended.
Can the method be adapted for automated or continuous monitoring, and what are the limitations?
The method is manual but could be automated using flow injection analysis (FIA) or sequential injection analysis (SIA) to handle reagent mixing and measurement. The total time of 15 min per sample is suitable for semi-continuous monitoring. Limitations include the need for pH adjustment and nitrogen purging, which require careful process control. Additionally, the method measures As(V) and total As, not As(III) directly, so As(III) is calculated by difference, which may accumulate errors at low concentrations.
Related Chinese Research & Cross-Citations
Analysis of National and Local Policies for Medical Waste Treatment and Disposal in China
The escalating generation of medical waste, driven by healthcare expansion and frequent medical activities, poses significant environmental and public health risks. Under the framework of ecological civilization, China is developing a comprehensive policy system for medical waste treatment and disposal, yet the current framework remains nascent and exhibits inconsistencies between national and local policies. This study systematically analyzes the status of national and local policies from 2003 to 2024, collecting 413 policy documents (166 from national ministries and 247 from provincial governments). The analysis examines temporal evolution, regional distribution, and policy focus, alongside the influence of medical waste output, treatment technologies, facility infrastructure, and major epidemic responses. Findings reveal distinct policy phases: initial self-disposal, exploratory management, foundational system building, and rapid development. Regional disparities are pronounced, with eastern coastal areas showing more advanced policies due to greater technical and financial resources. The surge in medical waste, particularly during the COVID-19 pandemic, underscores the need for enhanced regulatory guidance. Non-incineration technologies are gaining traction for their environmental and cost benefits, and facility coverage has improved but remains uneven. The study proposes five policy principles to foster technological innovation and industrial upgrading, ensuring safe medical waste management and environmental protection.
Kinetic Analysis and Simulation of Pollutant Removal in Sewage Networks
This study investigates pollutant removal characteristics and kinetic behaviors in sewage networks, and analyzes their impact on the carbon-to-nitrogen ratio (C/N, as COD/TN) of influent to wastewater treatment plants. Source water quality sampling at drainage outlets revealed spatial and temporal variations in C/N, with domestic sewage exhibiting higher C/N than industrial sewage, and diurnal peaks reaching 6.92 versus 4.71 during off-peak hours. Using a pilot-scale adjustable sewage network system in Kunshan, experiments were conducted under high (0.491 m·s−1) and low (0.089 m·s−1) flow velocities, monitoring pollutant removal over 144 hours. Pseudo-first-order kinetics were applied to model COD and TN removal. Results showed that COD (including SCOD and PCOD), BOD5, and SS achieved approximately 80% removal within 144 h, with higher removal at low flow velocity. TN, NH3-N, and TP exhibited lower overall removal rates. Kinetic fitting revealed that COD removal rate constants (kCOD) were significantly higher than those for TN (kTN), and both decreased with increasing flow velocity: at low velocity, kCOD=0.0167 h−1 and kTN=0.0029 h−1; at high velocity, kCOD=0.0127 h−1 and kTN=0.0020 h−1. Simulations based on actual source pollutant concentrations indicated that the time for C/N to drop to the denitrification critical value of 4.50 was 12.24 h at high velocity, but shortened to 9.49 h at low velocity. These findings demonstrate that increasing flow velocity effectively retards the decline of C/N. Therefore, regulating network flow velocity to reduce hydraulic retention time is a key strategy for maintaining adequate C/N at the terminal and ensuring denitrification efficiency in wastewater treatment plants.
Preparation of Trimetallic-Carbon Composite Catalysts and Their Application in Catalytic Ozonation of Industrial Wastewater
Advanced oxidation processes (AOPs) are promising for degrading organic pollutants in water treatment. Heterogeneous catalytic ozonation (HCO) has gained attention due to its high oxidation efficiency, strong interference resistance, and low secondary pollution. In this study, a series of trimetallic-carbon composite ozone catalysts were prepared via an organic precursor calcination method using γ-Al2O3 as support. This method enhanced catalytic activity and mechanical strength while overcoming the limitations of carbon materials (low mechanical strength) and metal-based materials (poor mass transfer). The optimized catalyst, CA-FeCoCu, comprising Fe, Co, Cu, carbon, and alumina, exhibited excellent performance in phenol degradation and real industrial wastewater treatment. Characterization revealed that the synergistic effect of trimetals and the introduction of multiple carbon types increased specific surface area and hydroxyl radical (·OH) generation. In a pilot-scale fixed-bed reactor, the CA-FeCoCu/O3 system reduced COD from 120 mg·L−1 to below 40 mg·L−1, with an O3 consumption ratio (O/C) of less than 1, effectively lowering operational costs. This work provides a new strategy for developing efficient and stable heterogeneous O3 catalysts and offers a reference for the practical application of HCO in industrial wastewater treatment.
Differentiated Characteristics of Suspended Particulate Matter and Their Effects on Water Quality in the Middle and East Routes of the South-to-North Water Diversion Project
This study investigates the spatiotemporal differentiation of suspended particulate matter (SPM) characteristics, sources, and their impacts on water quality between the Middle Route (closed artificial channel) and East Route (open natural water system) of the South-to-North Water Diversion Project. Thirty sampling sites (13 on the Middle Route, 17 on the East Route) were established, and samples were collected during dry and wet seasons. Water quality parameters and SPM characteristics were analyzed, including particle size distribution, total suspended solids (TSS), chlorophyll a, and stable carbon and nitrogen isotopes. Results show that the Middle Route maintains good and stable water quality, with SPM dominated by coarse particles (>63 μm, 61.43%–94.68%), total phosphorus (TP) <0.01 mg·L−1, and a significant positive correlation between chlorophyll a and coarse particles (r=0.60), indicating algal aggregation dominates particle formation. In contrast, the East Route exhibits high and fluctuating nitrogen and phosphorus concentrations, with SPM dominated by fine particles (<20 μm, 51.26%–88.61%), TP ranging from 0.03 to 1.11 mg·L−1, and a positive correlation with fine particles, suggesting significant external inputs. Carbon and nitrogen isotope analysis reveals that Middle Route SPM primarily originates from autochthonous algae (contribution >46.75%), while East Route SPM is influenced by both terrestrial C3 plants and algae. The distinct engineering and management approaches of the two routes lead to significant differences in SPM characteristics and sources, thereby affecting water quality dynamics. The Middle Route requires an 'algal reduction and hydrodynamic optimization' strategy to control algal-derived coarse particle deposition, whereas the East Route benefits from 'retention-sedimentation and wetland purification' to reduce external fine particles and pollutant inputs. This research provides theoretical support and practical guidance for differentiated SPM management in long-distance water diversion systems.
Combined Ozone Micro-Nano Bubble Oxidation and Powdered Activated Carbon Adsorption for Removal of Taste and Odor Compounds from Drinking Water
Algal-derived taste and odor compounds (2-methylisoborneol, 2-MIB, and geosmin, GSM) in drinking water sources are poorly removed by conventional treatment. This study systematically evaluated the standalone and combined performance of ozone micro-nano bubbles (O3-MNBs) oxidation and powdered activated carbon (PAC) adsorption for removing 2-MIB, GSM, and algal cells from source water. Results showed that O3-MNBs pre-oxidation achieved >97.5% removal of odorants at 400 ng·L−1 and 67.2% algal cell removal within 30 min. When applied as a deep treatment stage, the degradation rate constant (k) was 10.1%–25.6% higher than in pre-oxidation due to lower background matrix interference. Both pre-oxidation and deep treatment reduced effluent concentrations of 2-MIB and GSM to below 10 ng·L−1, with oxidation kinetics fitting pseudo-first-order models (R²>0.95). PAC adsorption of both compounds followed pseudo-second-order kinetics (R²>0.99), with GSM equilibrium adsorption capacity approximately 20.0% higher than that of 2-MIB. In pure water, adsorption capacity increased by >10.0% compared to raw water. Based on kinetic models, a quantitative prediction method was established for O3-MNBs oxidation and PAC adsorption processes, aiming to achieve efficient odorant removal and cost optimization, providing theoretical support for advanced drinking water purification and smart water plant construction.
Pulsed Electric Field Enhancement of Nitrogen Removal Performance and Microbial Community Structure Response in Anammox Granular Sludge
This study investigated the effects of a ring-shaped pulsed electric field (PEF) (1.5 V, 4 h on-time per cycle) on nitrogen removal performance and microbial community structure of anammox granular sludge (AnGS). Two anaerobic sequencing batch reactors (R1 control, R2 with PEF) were operated under stepwise increasing nitrogen loading rates (NLR). At NLR below 1,155 mg·(L·d)−1, R2 exhibited total nitrogen removal efficiency (TRE) 7.5%–17.0% higher than R1, with biomass, specific anammox activity (SAA), and extracellular polymeric substances (EPS) increased by 5%–7%, 21%–71%, and 54%–77%, respectively. However, at NLR above 1,320 mg·(L·d)−1, the toxic effect of nitrite dominated, and PEF enhancement diminished or even reversed to inhibition. Microbial community analysis revealed that at low-to-moderate NLR, PEF increased the relative abundance of Planctomycetes and key anammox bacteria (Candidatus Brocadia and Candidatus Jettenia), along with enhanced community richness (Chao1) and diversity (Shannon/Simpson indices). At high NLR, PEF decreased microbial richness compared to R1. Principal component analysis and redundancy analysis indicated that PEF was the key factor driving community differences at low-to-moderate NLR, whereas nitrite concentration became the dominant factor at high NLR. This study provides theoretical support for enhancing the resilience and engineering application of anammox processes.