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 initial solution of As(V) and Fe(III), experimental testwork has showed that a stable crystalline ferric arsenate is not synthesized at temperatures below 483.15 from liquors containing Fe(III) and as(III), through in-situ oxidation. Precipitations have been conducted at temperature range 483.15–553.15K. From these investigations, a crystalline form of ferric arsenate was possible only if the reaction was been carried out at temperatures above 483.15K. The XRD patterns of the compounds obtained revealed an unknown iron arsenic phase. The major considerations of this paper concern: 1. xture of ferric (III) sulfate and arsenic (III) oxides made up the initial solutions; explored range of precipitation temperatures which are investigated; udy of in-situ oxidation of arsenic(III) at high temperatures with hydrogen peroxide; e of solutions with concentrations similar to hydrometallurgical liquors; fect of some impurities to the ferric arsenate as well as materials choices for the reactor. aper points out also some engineering considerations regarding reactor design.