Pb2+ removal from aqueous solution using crab shell treated by acid and alkali

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Crab shell is a potential biosorbent for heavy metal removal.
• Understanding pretreatment effects is crucial for optimizing biosorption efficiency.

Purpose of the Study:

• To investigate the impact of acid and alkali pretreatment on lead (Pb(2+)) removal by crab shell.
• To elucidate the mechanisms behind enhanced Pb(2+) removal.

Main Methods:

• Crab shell was pretreated with hydrochloric acid (HCl) and alkali.
• Pb(2+) removal efficiency was measured for untreated, acid-treated, and alkali-treated crab shell.
• Transmission electron microscopy (TEM) was used to analyze structural changes.

Main Results:

• Acid pretreatment significantly reduced Pb(2+) removal due to demineralization (loss of Ca(2+) and Mg(2+)).
• Alkali pretreatment did not significantly alter Ca(2+) and Mg(2+) release but markedly reduced the time to reach equilibrium.
• TEM analysis provided insights into the structural modifications induced by alkali treatment.

Conclusions:

• Alkali pretreatment is a promising method for enhancing Pb(2+) removal efficiency by crab shell.
• Acid pretreatment is detrimental to Pb(2+) removal capacity.
• Structural changes, observable via TEM, likely explain the accelerated Pb(2+) adsorption kinetics after alkali treatment.