The possible use of kaolinitic clay, Giru clay, from Nigeria as an adsorbent for the removal of lead from water was investigated. Studies were carried out as a function of contact times, concentrations, temperatures and pH. The kinetics of adsorption as well as adsorption isotherms at different temperatures were equally studied. The results show that lead removal is favoured by low concentration, high temperature and acidic pH. The reasons for these observations are adduced.

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A comparative study of the contact angles of air bubbles, hydrocarbon oils (benzene and dodecane – both in the absence and in the presence of water‐soluble dodecylamine (laurylamine) chloride), flocculants and coagulants drops on flat polished coal surfaces immersed in water was made. The effect of the hydrocarbon chain length of some n‐alkylamine chlorides on the coal‐oil‐water was also investigated. The relationship of the measured contact angles to the flocculants, coagulants and dodecylamide chloride concentrations and pH was established. Results obtained show that maximum contact angles for the coals studied occur in the alkaline pH range (pH>7) for the systems investigated. Evidence is also provided to show that benzene and dodecane do not spread spontaneously on wet coal surfaces, even in the presence of a water‐soluble cationic surfactant. The results further show that the coal‐benzene water contact angles increase with an increase in the hydrocarbon chain length of the surfactant. Coagulants probably affect flotation of coal fines adversely, whereas flocculants have a remarkable effect on contact angles similar to that of surfactants.

in ultrafine powder form. The copper powders for the samples listed in Table 1, sample series A, B, and C, were Studies were made on copper/graphite based powders obtained by mechanical comminution (grinding) of pure and sintered compacts for industrial applications. The copper. The observed particle shapes were irregular rodlike, dependence of particle shape on friction in the powder acicular, flakelike, and angular. mass, compression ratio, and electrical receptivity ofThe copper powders for sample series D and E, given in powder metallurgy components was studied using Table 2, on the other hand, were purchased as imported near spherical precipitated copper powders and anguprecipitated copper with dendritic elongated, spherical lar or flakelike powders generated by mechanical rough, and pear shaped particle geometries. comminution. Results reveal that powders with particles that are nearly spherical in shape have lower friction, lower compression ratios, and higher electri-Methods cal resistivities in sintered compacts than powdersThe metal powders described above were sieved to obtain with acicular or flakelike particles. Also, the effects finer particles ranging from 75 to 600 mm (i.e. 75, 106, 150, produced by the small additions of lead and zinc (up 180, 200, 300, 400, and 600 mm). After sieving, the coarse to 2•5 wt-%) on the electrical resistivity and hardness particles (of sizes larger than 180 mm) were discarded, while of sintered copper-graphite compacts are also prethe particles between 75 and 180 mm, graded according to sented, and the influence of variation of briguetting size, were carefully mixed to obtain the desired particle size pressure is discussed.PM/0675 distribution. The sieving and particle mixing operations At the time the work was carried out the authors Table 1 Compositions of the various alloy powders studied, were at Metallurgical and Materials Engineering wt-% (Cu powder obtained by mechanical

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A comparative study has been carried out on the foundry qualities of synthetic moulding sand mixtures prepared from indigenous sand and clays of different plasticity (Enugu sand, Enugu fireclay and Ukpor clay). The effect of clay and water content on compressive strength and gas permeability in the green state was investigated. Results show that the more plastic Ukpor clay is a better binder and that moulding sand with up to 8 wt% fireclay, 3 wt% water; and 10 wt% Ukpor clay, 4 wt% water ensure a good combination of all working properties investigated. In the dry state the compressive and tensile strengths of the moulding sand showed a steady increase with increased clay content. With the addition of sawdust and coal dust, the latter showed best improvement on both the dry compressive and tensile strengths. Excellent collapsibility and high friability (12.53% for Ukpor clay‐bonded mixture and 10.35% for fireclay‐bonded mixture) were exhibited, but the friability values were reduced to about 1% by adding up to 3 wt% H2O for Ukpor clay‐bonded mixtures. The negative effect on the collapsibility was partially eliminated by the addition of 3 wt% sawdust. The study also shows that synthetic sand would be suitable for steel and general‐purpose casting, considering the low binder contents of the mixtures.

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