Phosphate removal by lead-exhausted bioadsorbents simultaneously achieving lead stabilization

Area of Science:

• Environmental Chemistry
• Materials Science
• Waste Management

Background:

• Developing low-cost adsorbents for heavy metal removal is crucial, but their subsequent treatment remains a challenge.
• Effective strategies are needed to manage toxic metal-laden adsorbents and mitigate environmental risks.

Purpose of the Study:

• To investigate an optional strategy for treating heavy metal-impregnated adsorbents by employing them for phosphate retention.
• To evaluate the potential of lead-sorbed adsorbents for enhanced phosphate removal and metal stabilization.

Main Methods:

• Several raw or modified waste biomass types were tested for phosphate adsorption enhancement by sorbed lead.
• Tea waste-supported hydrated manganese dioxide (HMO-TW) loaded with lead (HMO-TW(Pb)) was selected for systematic phosphate retention evaluation.
• Phosphate adsorption kinetics, pH influence, competing anion effects, and lead leaching were analyzed.

Main Results:

• Phosphate adsorption onto HMO-TW(Pb) was largely pH-insensitive and unaffected by competing anions due to surface precipitation.
• No lead leakage was observed from HMO-TW(Pb) during phosphate adsorption across a wide pH range and high ionic strength.
• Phosphate adsorption was rapid (<60 min equilibrium time) and temperature-independent, with successful application in a fixed-bed column test.

Conclusions:

• Employing lead-laden adsorbents for phosphate retention offers a viable strategy for stabilizing toxic metals and reducing environmental risks.
• HMO-TW(Pb) demonstrates practical applicability for efficient phosphate removal from water, addressing the challenge of post-treatment for heavy metal adsorbents.