Formation of Cr(III) hydroxides from chrome alum solutions. 1. Precipitation of active chromium hydroxide.

MARCELO J. AVENA; CARLA E. GIACOMELLI; CARLOS P. DE PAULI

JOURNAL OF COLLOID AND INTERFACE SCIENCE

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 1996 vol. 180 p. 428 - 435

0021-9797

The formation of active chromium hydroxide, Cr(OH) 3 3H 2 O, was studied through potentiometric titrations and turbidimetric measurements. UV-Vis and IR spectroscopies were also employed to characterize the synthesized solid. The rapid addition of NaOH solution to aqueous chrome alum (KCr(SO 4 ) 2 12H 2 O) solutions caused the immediate precipitation of the active material. Only monomeric Cr(III) species seemed to be participating in the precipitation process; neither chromium polymers nor complexes with anions (SO 20 4 , Cl 0 , NO 0 3 , ClO 0 4 ) influenced the fast formation of Cr(OH) 3.3H 2 O. Titration studies allowed the determination of several hydrolysis and precipitation constants for Cr(III). Nevertheless, they cannot be used for the estimate of Cr(OH) 03 formation constant.