Studies on the application of alkyl hydroxamates in the flotation of cassiterite from an Indian tin ore

The Tosham tin ore in Bhiwani district of Haryana is the biggest lode type tin deposit in India having cassiterite as the chief tin mineral. The cassiterite in this ore is strongly paramagnetic due to sub-microscopic inclusions of magnetite. Beneficiation studies on this ore by a combination of gravity and magnetic separation techniques have indicated a loss of about 25-30% of tin values in various tailings streams, consisting predominantly of liberated cassiterite of size< 15-20 mu m and ultrafine size cassiterite dispersed in gangue silicate minerals. This paper presents results of the flotation studies carried out for the recovery of fine size cassiterite from the gravity tailings of Tosham ore using alkyl hydroxamic acid type collector reagents. The investigation include study on the interrelationship between flotation pH, chain length of the collector and particle size of mineral, taking pure cassiterite of Tosham and alkyl hydroxamates. and application of the understanding from microflotation results on natural sample, at both bench and large scale. Pure cassiterite from Tosham ore gave good flotation response with alkyl hydroxamate collectors due to the strong complexation of the reagents with both tin and iron ions. The amount of cassiterite floated increases and the pH range of good flotation widens, as the particle size becomes finer(<75 pm) or when the chain length of the surfactant is higher (C10 and more). The flotation experiments on gravity tailings of Tosham tin ore indicated higher selection and collection efficiencies with potassium decyl hydroxamate compared to octyl or tetra-decyl analogue. Selectivity and Kinetics were better at about pH 4.6 than at higher pH. Large scale flotation test under optimum flotation conditions gave a final float product analysing about 7% Sn with about 55% overall recovery with potassium decyl hydroxamate. The tin assay of the final float meets the specifications required for further metallurgical upgradation of Sn content by chemical fuming technique.