The Estimation of Free Iron Oxides in Soils and Clays and Their Removal

Abstract

THE estimation and removal of the free iron oxides resent in soils are of considerable interest in view of the importance o P iron oxides in the process of odzolization, laterization, and phosphate fixation. The removal of P ree iron oxides also facilitates the identification and estimation of minerals present in soils and clays by X-ray, petrographic, and thermal analyses.A number of methods has been suggested since Tamm (1922) first proposed acid ammonium oxalate to remove free oxides of silicon, aluminium, and iron. Mattson (1931) used hot saturated aluminium chloride to remove the free sesquioxides from clays. Drosdoff and Truog (1935) found that when soil or clay suspensions were saturated with hydrogen sulphide under alkaline conditions, free iron oxides were converted into sulphides which could subsequently be removed by 0.05 N hydrochloric acid. This treatment dissolved finely ground ferric oxide, but had no appreciable effect on the iron in biotite, basalt, and granite. Truog and co-workers (1936) later modified the method. Instead of passing hydrogen sul hide through the suspension, nascent hydrogen sulphide was produce c f within the suspension by the action of oxalic acid on sodium sulphide. The iron sul hide was dissolved by the stable towards the reagent, but the iron exchange complex was less stable. Jeffries (1941) pro osed a method for removing iron oxides from action of nascent hydrogen produced by the action of oxalic acid on an aluminium cylinder immersed in a boiling solution. Dion (I 44) modisoil suspension with 10 per cent. ammonium tartrate in presence of metallic aluminium. Allison and Scarseth (1942) used anaerobic decomposition of a sugar solution in soil to reduce the iron oxide to the ferrous and soluble state.The present investigation was carried out in an attempt to find a suitable method or modification of existing methods for estimating and removing free iron oxides from soils and clays without affecting the other clay minerals. With this end in view preliminary experiments were carried out to find the effect of:(I) Soil-solution ratio, 2 Time of digestion or shaking, I) 3 Effect of repeated treatments, on the removal of iron oxides by different methods. The soil used was a subsoil from Knott Wood, Rothamsted. Organic matter was destroyed by the action of hydrogen peroxide and the oxalic acid. The aluminium exchange comp e ex was found to be quite sand and silt for minera f ogical estimation. Iron was reduced by the fied the method of Jeffries and carried out the reduction by R eating the

Reactivity of Clay Minerals With Acids and Alkalies

“…The Fe20:~ present was determined colorimetrically with KCNS and deduced from the total weight of the precipitate to give AI203 by difference. Free iron oxide in samples (A), (B), (C), (D), and (E) was removed by treatment with dithionate at 40~ (Deb, 1950) and determined colorimetrically with KCNS. The free iron in samples (F), (G), and (H) given in Table 3 is from the analyses in Table 2, as all the iron in these clays is considered to be free iron oxides coating the clay particles.…”

Uranium Adsorption from Aqueous Solution Using Sodium Bentonite Activated Clay

“…[3,4]. The thoroughly-wetted clay (20-40 mg.) is treated with a fresh 4% sodium chloride solution of pH 5.8-6.0 (adjusted by sodium hydroxide solution) at ~ 40-45°C for 15 minutes.…”

“…Their sorption capacities are usually less than those of synthetic sorbents; these materials could provide an inexpensive substitute for the treatment of heavy metal for wastewaters. To enhance the sorption capacity; the clays are modified in various ways, such as treatment by inorganic and organic compounds, acids and bases [3,4]. For example, montmorillonite, coated and intercalated by aluminum hydroxide exhibits much higher adsorption capacity for some heavy metal ions, than that of natural montmorillonite [5].…”

Transformation Experimentale De Chlorite En Montmorillonite

“…Comme ce sont des silicates essentiellement ferrif6res, au lieu d'op6rer une attaque acide nous avons utilis6 des solutions mixtes renfermant un sel r6ducteur, l'hydrosulfite de sodium, et un agent complexant; le tartrate de sodium (Deb, 1950).…”