GB484902A - Improvements in or relating to soil improvers - Google Patents

Abstract

Soil improvers are obtained by reacting materials containing a substantial amount of water-insoluble humin acids, which by the addition of monovalent bases have been brought into dissolved or sol or gel condition, with aluminium and/or iron ions in the absence of phosphate ions, or with aluminium and/or iron compounds in sol or gel condition, the pH value of the reacting mixture being maintained between 4 and 8 and the proportion of aluminium and/or iron in the final product calculated as Al2O3 and or Fe2O3 being about 1-5 per cent of the dry organic matter. Sodium, potassium and ammonium are suitable monovalent bases. Suitable humin acid-containing materials may be obtained by subjecting fossil or recent organic materials, e.g. sphagnum peat, straw, refuse from sugar factories, lignite and charcoal, while in moist condition to oxidation with a free oxygen containing gas such as air at elevated temperatures not above 130 DEG C. while maintaining the pH value between 5 and 9. Aluminium may be introduced as a solution of bauxite or clay in sulphuric acid, aluminium sulphate, aluminium chloride or aluminium hydroxide sol or gel. During the formation of the soil improver, aluminium and/or iron salt solutions and the mono-valent base, preferably ammonia may be added alternately to the material containing humin acids. The product can be partially saturated with calcium and/or magnesium ions by adding limited amounts of calcium and/or magnesium compounds, e.g. calcium hydroxide, before, during or after the reaction between the humin acid containing material and the aluminium and/or iron. The oxidation of the fossil or recent organic materials may be effected before, during or after the addition of the aluminium and/or iron compounds. The initial material may be digested at elevated temperature with water, preferably rendered and/or alkaline, before or after the oxidizing process. The digestion should preferably be followed by washing with water. When the reaction is completed the product can be precipitated by adjusting the pH to 4,5-5. After filtration and drying the pH of the final product may be adjusted to 6-8, say 7, by the addition of ammonia with or without calcium hydroxide. Specification 438,114 is referred to.