Arsenic sorption on TiO2 nanoparticles: size and crystallinity effects

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Titanium dioxide (TiO2) nanoparticles are crucial in environmental remediation.
• Understanding arsenic (As) sorption on TiO2 is vital for water purification.
• Nano-sized TiO2 properties vary with size and crystallinity, impacting contaminant removal.

Purpose of the Study:

• To investigate arsenic (III) and arsenic (V) sorption on amorphous and crystalline nano-TiO2.
• To determine the effects of TiO2 size and crystallinity on arsenic sorption capacity.
• To explore arsenic oxidation and surface complexation mechanisms on TiO2.

Main Methods:

• Sol-gel synthesis for amorphous and crystalline nano-TiO2 preparation.
• Sorption isotherm studies to quantify arsenic uptake.
• X-ray absorption spectroscopy (XAS) for speciation and complex analysis.

Main Results:

• Sorption capacity is influenced by TiO2 site density, surface area, and crystallinity.
• As (III) surface coverage was constant on 5-20 nm particles, while As (V) coverage increased with crystallinity.
• Partial As (III) oxidation occurred on amorphous TiO2; both As species formed binuclear complexes on amorphous TiO2 at neutral pH.

Conclusions:

• Nano-TiO2 size and crystallinity significantly affect arsenic sorption.
• Amorphous TiO2 can partially oxidize As (III), influencing its fate and transport.
• Specific surface complexation mechanisms were identified for As (III) and As (V) on nano-TiO2.