Efficient approach for Cd2+ and Ni2+ removal and recovery using mesoporous adsorbent with tunable selectivity

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Cadmium pollution from nickel-cadmium (NiCd) batteries is a significant environmental issue, particularly in developing nations.
• Adsorption is a cost-effective and straightforward method for removing heavy metals from contaminated water.
• Mesoporous materials like NH2-MCM-41 show promise for adsorbing cadmium (Cd2+) and nickel (Ni2+) ions.

Purpose of the Study:

• To demonstrate the use of competitive complexation for achieving high adsorption selectivity for Cd2+ or Ni2+ using NH2-MCM-41.
• To investigate the influence of chelating agents, pH, and metal concentrations on adsorption selectivity and capacity.
• To develop a reusable and selective adsorbent for heavy metal remediation.

Main Methods:

• Synthesized mesoporous NH2-MCM-41 as an adsorbent.
• Conducted single and binary component adsorption studies with Cd2+ and Ni2+ ions.
• Manipulated adsorption selectivity by adjusting ethylenediaminetetraacetic acid (EDTA) concentration and solution pH.
• Analyzed adsorption capacities and selectivity using spectroscopic methods.

Main Results:

• Achieved on-demand 100% selectivity for either Cd2+ or Ni2+ adsorption by controlling EDTA concentration and pH.
• NH2-MCM-41 adsorbed cadmium selectively (0.56 mmol g-1) at [EDTA]/[M2+] = 0.5 and pH 5.
• NH2-MCM-41 adsorbed nickel selectively (0.50 mmol g-1) at [EDTA]/[M2+] = 0.5 and pH 2.
• The adsorbent was regenerated effectively via acid washing and reused without performance loss.

Conclusions:

• The competition between complexant and sorbent offers a novel strategy for highly selective heavy metal adsorption.
• NH2-MCM-41, when combined with a chelating agent like EDTA, provides tunable selectivity for cadmium or nickel removal.
• This method presents a sustainable and efficient approach for remediating heavy metal pollution from industrial sources.