Immobilization of arsenic in crystalline form from aqueous solution by hydrothermal processing above 483.15K

Although FeAsO4 can be precipitated at temperatures less then 473.15 with i nitial solution of As(V) and Fe(III), experimental testwork has showed that a stable crystalline ferric arsenate is not synthesized at ternperatures b elow 483.15 from liquors containing Fe(III) and As(III), through in-situ ox idation. Precipitations have been conducted at temperature range 483.15-553 .15K. From these investigations, a crystalline form of ferric at-senate was possible only if the reaction was been carried out at temperatures above 4 83.15K. The XRD patterns of the compounds obtained revealed an unknown iron arsenic phase. The major- considerations of this paper concern: The mixture of ferric (III) sulfate and arsenic (III) oxides made up the in itial solutions. The unexplored range of precipitation temperatures which are investigated. The study of in-situ oxidation of arsenic(III) at high temperatures with hy drogen peroxide. The use of solutions with concentrations similar to hydrometallurgical liqu ors. The effect of some impurities to the ferric arsenate as well as materials c hoices for the reactor This paper points out also some engineering consider ations regarding reactor design. (C) 2001 Elsevier Science Ltd All rights r eserved.