Clive Mitchell

Laboratory evaluation of kaolin: a case study from Zambia

Abstract Kaolin is principally used as a white pigment in the manufacture of paper and whiteware ceramics and in paints, rubbers and plastics. The desirable properties of kaolin in these end uses include chemical purity, high kaolinite content, fine particle size, euhedral kaolinite platelets, high brighteness values and appropriate rheology. This paper outlines the laboratory evaluation of a kaolin from Chilulwe, near Serenje, Central Province of Zambia. The kaolin occurs in a hydrothermally-altered feldspar pegmatite within a granite-gneiss basement. Initial laboratory characterization of the kaolin showed it to consist mainly of microcline feldspar (80%) with 17% kaolinite and trace quantities of muscovite, beryl and tourmaline. A kaolinite concentrate, produced by wet screening and hydrocloning, contained 79–87% kaolinite, with a clay (< 2 µm) content of 58%, a brightness of 70–76% (86–870n firing) and a viscosity concentration of 68%. Transmission electron microscopy showed the kaolinite to consist of rolled and hexagonal crystals. The results of this study showed that the Chilulwe kaolin, and by-product K-feldspar, have potential as a raw material for manufacture of ceramic products.

FarmLime: low-cost lime for small-scale farming

Abstract In the less-developed parts of southern Africa, where agriculture is crucial in daily survival, agricultural lime is often difficult to obtain. This is due to the scarcity of production sites, high transport costs and inadequate support for farmers from government extension services. In Zambia there are upwards of 700 000 small-scale farmers who struggle to farm on acid soils and as a result have poor crop yields. They cannot afford to use agricultural lime, which would solve the problem, and as a result are trapped in a cycle of poverty. In an attempt to address this problem, the UK research project ‘FarmLime’, based in Zambia, investigated a means of producing affordable agricultural lime using simple, locally available technology. Dolomite suitable for agricultural lime occurs throughout Zambia, including those farming districts with acidic soils. It is estimated that small-scale production using partly manual methods could produce agricultural lime for US

A pilot study on iodine in soils of Greater Kabul and Nangarhar provinces of Afghanistan

25 – 30 per tonne. Demonstration crop trials were successful in demonstrating the benefits of using agricultural lime to small-scale farmers. Where the price of maize is high and the cost of lime is low, the economic benefits of its use are high. However, even if there is a demonstrable economic benefit, the use of agricultural lime will be constrained by the lack of cash in the rural economy; one potential solution to this could be bartering of crops for agricultural lime.