Determination of Hexavalent Chromium (Cr(VI)) Concentrations via Ion Chromatography and UV-Vis Spectrophotometry in Samples Collected from Nacogdoches Wastewater Treatment Plant, East Texas (USA)

Figure 3

((a) and (b)) Chromatogram of Cr⁺⁶ in aeration chamber (a) and clarifier (b). A Dionex ICS-2100 ion chromatograph was used with the following conditions: Dionex IonPac CS5A, 4 × 250 mm column; Dionex IonPac CG5A, 4 × 50 mm guard column; eluent flow rate: 0.36 mL/min; injection volume: 5000 μL; temperature: 30°C; back pressure: 200–3000 psi; postcolumn reagent system conditions: flow rate: 0.12 mL/min; detection: visible absorbance, 530 nm; noise: 6–8 μAU; runtime: 10 minutes. ((c) and (d)) Chromatogram of Cr⁺⁶ in chlorine contact chamber (c) and sulfur dioxide chamber (d). A Dionex ICS-2100 ion chromatograph was used with the following conditions: Dionex IonPac CS5A, 4 × 250 mm column; Dionex IonPac CG5A, 4 × 50 mm guard column; eluent flow rate: 0.36 mL/min; injection volume: 5000 μL; temperature: 30°C; back pressure: 200–3000 psi; postcolumn reagent system conditions: flow rate: 0.12 mL/min; detection: visible absorbance, 530 nm; noise: 6–8 μAU; runtime: 10 minutes.

(a) Aeration

(b) Clarifier

(c) Chlorination

(d) SO₂