HYDROXY-CHROMIUM SMECTITE

Hydroxy-chromium solutions were prepared from chromium nitrate solutio ns by adding NaOH with OH/Cr = 2. The solutions were treated at 20-deg rees-C and 60-degrees-C. The hydrolysis times were from 1 to 100 days. Polymeric species in hydrolyzed chromium solutions were followed by v isible absorption spectra within the range 325-800 nm and by pH measur ement. OH-Cr-smectite with high d(001) spacing (2.07 nm) was obtained when hydroxy-chromium solution was prepared at 60-degrees-C and with 1 -day hydrolysis. When this sample was heated up to 350-degrees-C, the basal spacing collapsed at 1.8 nm. The samples were characterized by X -ray diffraction and N2 adsorption-desorption isotherms.