Boosting Cu ion capture in high-salinity environments with amino-functionalized millispheres

Area of Science:

• Environmental Chemistry
• Materials Science
• Adsorption Science

Background:

• High salinity in wastewater challenges traditional adsorbents by disrupting electrostatic interactions and ion exchange.
• Limited efficiency of existing adsorbents in saline environments necessitates novel solutions for heavy metal removal.

Purpose of the Study:

• To investigate the salt-promoted adsorption of copper (Cu) ions onto amino-functionalized chloromethylated polystyrene (EDA@CMPS) millispheres.
• To understand the mechanisms behind enhanced Cu adsorption in saline wastewater.

Main Methods:

• Synthesis of EDA@CMPS by grafting ethylenediamine (EDA) onto chloromethylated polystyrene (CMPS).
• Adsorption experiments conducted in both saline and non-saline solutions to compare Cu ion uptake.
• Mechanistic analysis using techniques to study protonation, ionic strength effects, and Cu speciation.

Main Results:

• EDA@CMPS exhibited nearly three times higher Cu adsorption capacity in saline solutions (1.65 mmol g⁻¹) compared to non-saline solutions (0.66 mmol g⁻¹).
• Salt presence promoted amino group protonation on EDA@CMPS, increasing positive charge and Cu ion affinity.
• Increased ionic strength enhanced Cu adsorption by reducing electrostatic repulsion and altering Cu speciation to favor complex formation.

Conclusions:

• Amino-functionalized chloromethylated polystyrene is an effective adsorbent for Cu ions, especially in high-salinity wastewater.
• Salt-promoted mechanisms, including enhanced protonation and altered speciation, significantly improve adsorption performance.
• This study offers a viable strategy for efficient heavy metal remediation in challenging saline wastewater environments.