Modular hydrogel selectively adsorbs phosphates and hexavalent chromium while enabling phosphate recovery

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Electroplating wastewater poses significant environmental risks due to high concentrations of phosphates and hexavalent chromium (Cr(VI)).
• Phosphorus recovery is crucial for sustainable development, given its status as a non-renewable resource.
• Existing treatment methods often lack efficiency or reusability for complex wastewater streams.

Purpose of the Study:

• To develop an efficient adsorbent for simultaneous removal of phosphates and Cr(VI) from electroplating wastewater.
• To investigate the potential for phosphorus recovery from treated wastewater.
• To evaluate the performance and reusability of the developed adsorbent material.

Main Methods:

• Fabrication of a modular hydrogel (LC-CSP) using sodium alginate, chitosan, lanthanum carbonate, and polyethyleneimine (PEI).
• Characterization of the hydrogel's structure, morphology, and adsorption properties.
• Testing adsorption capacities and removal efficiencies for phosphates and Cr(VI) under various conditions, including simulated wastewater with interfering substances.
• Assessing the reusability of the hydrogel over multiple adsorption-desorption cycles.
• Investigating adsorption mechanisms using multiple characterization techniques.
• Conducting fixed-bed adsorption experiments to evaluate practical applicability.

Main Results:

• The LC-CSP hydrogel exhibited high adsorption capacities: 232.02 mg/g for phosphates and 474.61 mg/g for Cr(VI).
• The material demonstrated excellent reusability, retaining over 83% performance after five cycles.
• High removal efficiencies (>90.72%) were maintained for both pollutants in simulated wastewater containing interfering substances.
• Adsorption mechanisms involved ligand exchange, electrostatic interactions, and hydrogen bonding for phosphates, and electrostatic interactions, hydrogen bonding, and reduction for Cr(VI).
• Fixed-bed experiments confirmed the technical feasibility of LC-CSP for electroplating wastewater treatment and phosphorus recovery.

Conclusions:

• The fabricated LC-CSP modular hydrogel is a promising material for the simultaneous removal of phosphates and Cr(VI) from electroplating wastewater.
• The study highlights the potential for resource recovery (phosphorus) from industrial wastewater.
• LC-CSP demonstrates excellent stability, reusability, and efficiency, indicating its strong potential for practical environmental applications.