Activated carbon with excellent chromium(VI) adsorption performance prepared by acid-base surface modification

Area of Science:

• Environmental Chemistry
• Materials Science

Background:

• Hexavalent chromium (Cr(VI)) poses significant environmental and health risks.
• Conventional methods for Cr(VI) removal often struggle with efficiency at low concentrations.

Purpose of the Study:

• To develop an activated carbon (AC) material with enhanced Cr(VI) adsorption performance, particularly at low concentrations.
• To investigate the effects of acid-base surface modification on AC properties and Cr(VI) adsorption.

Main Methods:

• Activated carbon was modified using nitric acid oxidation followed by sodium hydroxide and sodium chloride treatment.
• Batch equilibrium and continuous column adsorption experiments were performed.
• Surface properties and pore structure were characterized using Boehm titration, elemental analysis, and N(2)/77K adsorption isotherms.

Main Results:

• The modified AC (AC(2)) demonstrated superior Cr(VI) adsorption capacity and rate compared to modified (AC(1)) and raw (AC(0)) AC.
• Modification led to decreased surface area (S(BET)) but increased surface oxygen acidic groups.
• NaOH treatment neutralized surface acidity, contributing to enhanced adsorption.

Conclusions:

• The HNO(3)-NaOH modification method is effective in preparing high-quality AC for Cr(VI) removal.
• Increased oxygen surface acidic groups and suitable surface acidity are key factors for improved Cr(VI) adsorption.
• This approach shows promise for the efficient removal of low concentrations of Cr(VI) from aqueous solutions.