At what pH range is hexavalent chrome reduced?

Hexavalent chromium, often found in industrial wastewater, is typically reduced to trivalent chromium, which is less toxic, at a lower pH range. The optimal pH for the reduction of hexavalent chromium occurs around 2 to 2.5. At this acidic pH, the chemical environment is highly conducive for the reduction reaction to take place, often facilitated by reducers such as sulfite or other reducing agents.

In the acidic conditions, hexavalent chromium is more prone to gaining electrons and transforming into its less harmful trivalent form. This is an important aspect of wastewater treatment processes since reducing the toxicity of chromium contaminants is crucial for environmental safety and regulatory compliance.

Other pH ranges, such as 5-6, 7-8, or 10-11, are not suitable for the effective reduction of hexavalent chromium. At these higher pH levels, the reactivity of the hexavalent chromium decreases, making the reduction process less efficient. Hence, the specific conditions and chemical principles applied in the lower pH range justify why this choice is the correct answer.