| Abstract
| - A nanostructured, porous material was prepared by heterocoagulation of negatively charged montmorillonite with positively charged synthetic spherical hematite particles. The process of heterocoagulationof such particles was monitored by turbidimetric titrations over the pH range 2.5−7.5. On the basis of theresults of turbidimetric measurements, a series of solid materials were prepared for further characterizationusing ESEM, BET, XRD, and FTIR techniques. Environmental scanning electron microscopy detectedisolated hematite particles or small hematite aggregates on montmorillonite surfaces (mass ratios 8:1 and4:1). At a mass ratio of 1:1, exfoliated montmorillonite layers, covering the hematite particles as semi-transparent blankets were seen. A low mass ratio led to compact hematite particle aggregates coveringthe montmorillonite surfaces. Nitrogen-gas-adsorption isotherms revealed the sorption properties to begradually dependent upon mass ratios. Pore volume distributions showed that mesopores with diameterof about 10−20 nm were produced in the heterocoagulates with mass ratios of 4:1, 1:1, and 1:8. The sampleprepared with a 4:1 mass ratio showed the greatest BET surface area, which decreased slightly uponsample calcination at 500 °C. X-ray diffraction measurements were used to investigate layer stacking, bycomparing the integral intensities of d001 reflection. For this purpose, samples with 4:1 mass ratios, preparedboth by heterocoagulation and mechanical grinding, were used. It was found that heterocoagulation effectivelydiminished the stacking of the layers to about 85%; hence, a significant amount of fundamental, 1 nm thickmontmorillonite layers was achieved in this sample.
|
