Zirconium-modified biochar as the efficient adsorbent for low-concentration phosphate: performance and mechanism

Area of Science:

• Environmental Science
• Materials Science
• Water Treatment

Background:

• Water eutrophication is a major environmental concern, driven by phosphorus discharge.
• Stringent wastewater standards necessitate advanced phosphorus removal technologies.

Purpose of the Study:

• To synthesize and evaluate a low-cost, high-efficiency phosphate adsorbent.
• To investigate the adsorption performance and mechanism of zirconium-modified biochar (ZrBC) for low-concentration phosphate.

Main Methods:

• Biochar synthesized from peanut shell powder via pyrolysis.
• Zirconium modification using co-precipitation.
• Phosphate adsorption experiments (batch and column).
• Adsorption kinetics and isotherm modeling (pseudo-second-order, Langmuir).

Main Results:

• ZrBC achieved 100% phosphate removal from low-concentration solutions (<1 mg·L⁻¹).
• Maximum adsorption capacity reached 58.93 mg·g⁻¹ at 25°C.
• Adsorption followed pseudo-second-order kinetics and Langmuir isotherms, indicating chemical, single-layer adsorption.
• Ligand exchange with surface hydroxyl groups was the primary adsorption mechanism.
• ZrBC demonstrated high capacity in column experiments (190 h breakthrough time for 0.5 mg·L⁻¹ effluent).

Conclusions:

• ZrBC is a cost-effective and efficient adsorbent for low-concentration phosphate removal.
• The material shows significant potential for treating secondary effluents from municipal wastewater treatment plants (WWTPs).
• ZrBC offers an environmentally friendly solution for preventing water eutrophication.