Cassiterite introduction

The chemistry of cassiterite flotation has been a subject of considerable research for many years. The findings that sulphosuccinamates, phosphonic acid and arsonic acid were selective collectors for cassiterite flotation lead to the introduction of flotation as a complementary recovery process to gravity concentration at most primary tin mill concentrators in the early 1970s. In spite of continued research, subsequent progress in development has been rather limited. Cassiterite flotation still remains a secondary tin recovery process in most plants, for beneficiation of cassiterite below 40 pm size. 

This collector has the formula shown in Figure 21.3. The identification of /7-tolyl arsonic acid as a selective collector for cassiterite flotation led to the introduction of this collector into many industrial plants. The first recorded industrial use of /7-tolyl arsonic acid was at the Alterberg mine in Germany. By the early 1970s, this collector was introduced into a number of operations, including Rooiberg and Union Tin (South Africa), the Renison and Cleveland tin mines (Australia). 

Fusion decomposition provides an alternative digestion method. This is a high-temperature technique where powdered samples are heated with a suitable flux to produce a residue that may be readily dissolved. Fusion decompositions are the most rigorous digestions available and all silicate materials can be brought into a complete solution when fused with an appropriate flux. The principal disadvantage of the fusion technique is the introduction of extra salts into the final solution from the flux (thereby increasing total dissolved solids). Fusion decomposition remains the preferred technique for quantitative analysis of silicon, and may be the only practical method for complete decomposition of refractory minerals such as zircon, rutile, and cassiterite. Many fluxes have been used, but perhaps the most commonly used is lithium metaborate (LiBOs). This flux introduces only Li and B into the final solution, and is used at a relatively low flux sample ratio of 3 1. 

Some materials are particularly resistant to acid digestion, e.g., certain rocks, mineral oxides, phosphates, and some iron alloys. For these samples, high-temperature fusion with an acidic or basic flux such as lithium metaborate (LiBOs) in the molten state can be used to render such materials soluble in water or dilute acid. Fusion decompositions are the most rigorous methods available and all silicate materials, including refractory substances like zircon and cassiterite, can be dissolved completely when fused with an appropriate flux. However, there are several disadvantages to this method including the introduction of additional salts into the final solution... 

---