リサイクルと廃棄物管理の進歩

Metals of lead and some lead alloys, lead oxide, nickel and cobalt were recovered from exhausted grids of electrolyte-free rechargeable lead batteries by combining hydrometallurgy and pyrometallurgical method. The spent grids were leached in hot 2 M and 5 M nitric acid. The unleached fraction was heated with sodium carbonate to produce lead oxide. The leachants were analyzed by Inductively coupled plasma mass spectrometry (ICP). Lead was precipitated as hydroxide on cold with ammonia. Nickel and cobalt metals in solution were extracted by solvent extraction using LEWATIT MP 600 ion exchange resin. Metals loaded by the organic phase were stripped by HCl. Metal hydroxides were reduced with ascorbic acid or hydrazine hydrate to ultrafine free metals, Lead alloys were prepared by encapsulating the alloying metal oxide or organic salts in the host lead metal and heated at 800°C. The end products were investigated with Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray fluorescence (XRF), ICP and scanning electron microscope (SEM). Results revealed that the spent grids contain 94.2% lead, aluminium 0.12%, nickel 0.05% and cobalt 0.053%. The particle size of the reduced metals was found in range of 15-60 um, LEWATIT MP 600 ion exchange resin is specific adsorbent for nickel and cobalt. Distribution constant (Kd) value of the stripping step decreased in the order Ni and Co. Lead-Al-Mg alloy was prepared by heat treatment of terminal taps at 500°C. The obtained lead alloys were investigated with EDX and SEM. Lead calcium alloy was homogeneous and contain calcium particles with 5 ums.

The study evaluates solid waste management techniques in two selected markets in Ibadan in order to determine solid waste management for the purpose of efficient utilization potentials and economic benefits. The markets selected are Aleshinloye and Bodija markets which are built to meet national standard. Oral interview was conducted on the randomly selected respondents using well-structured questionnaires and review of published literature was also adopted for this study. The nature and composition of solid waste generated, disposal techniques, recycling, and potentials of waste management techniques in relation to the socio-economic characteristics of the traders in the markets were investigated. 200 questionnaires were administered to the study areas and the data obtained were analyzed using frequency, bar charts and chi-square for the solid waste techniques between both markets. The findings showed that there are variations in all the variables and revealed that the techniques used for waste management in both markets were inadequate. It was recommended that awareness campaign should be set up for proper waste management process through proper education among the traders especially. This paper also suggests that State and local government should collaborate with other environmental agencies in managing, constructing and building waste recycling plant and government should assist in other logistics to allow smooth running of the factory. Finally, it was recommended that urban renewal strategy should also be adopted for future reference.