Characterisation of automotive shredder residue

The autofluff residue of a Portuguese shredding facility was characterised aiming at identifying the presence of heavy metals in several constituents of these residues, in order to propose possible valorising solutions. Particle size analysis showed that average characteristic diameter (d50) was 6.5 mm, the coarser fractions (> 11 mm, representing 40% of weight) being essentially composed of plastic pieces, rubber, foams and textiles, particles in the range 2-11 mm being composed of mixed materials, while in particles below 2 mm (referred as fines) the presence of glass, ceramics and other inorganic materials became very frequent, in spite of a very fine foam was also detected in the very fine fractions. XRD analysis of fines allowed detecting the crystalline phases quartz, calcite, rutile and magnetite. Elemental analysis by EDXRF was carried out on several fractions in the particle size range 0.02-2.0 mm, showing the presence of practically all the elements detected in all fractions, namely Fe, Zn, Cu, Pb, Ba, Sn, and also traces of Cd, Sb, Mo and Sr. Some of these metals are hazardous and can be problematic in what concerns the possible valorisation of the residue

THE WORLD MARKET FOR SOYBEANS: PRICE TRANSMISSION INTO BRAZIL AND EFFECTS FROM THE TIMING OF CROP AND TRADE

This paper investigates the price transmission in the world market for soybeans using time series econometrics models. The theoretical model developed by Mundlack and Larson (1992) is based on the Law of the One Price, which assumes price equalization across all local markets in the long run and allows for deviations in the short run. The international market was characterized by three relevant soybean prices: Rotterdam Port, Argentina and the United States. The paper estimates the elasticity of transmission of these prices into soybean prices in Brazil. There were carried causality and cointegration tests in order to identify whether there is significant long-term relationship among these variables. There was also calculated the impulse-response function and forecast error variance decomposition to analyze the transmission of variations in the international prices over Brazilian prices. An exogeneity test was also carried out so as to check whether the variables respond to short term deviations from equilibrium values. Results validated the Law of the One Price in the long run. In line with many studies, this paper showed that Brazil and Argentina can be seen as price takers as long as the speed of their adjustment to shocks is faster than in the United States, the latter being a price maker. An interesting conclusion was reached when the pattern of the impulse response functions was compared to the timing of crop and trade in Brazil, Argentina and the United States. These seasonal differences may help explaining the pattern of the response of Brazilian prices to shocks in the international market, especially that the response from shocks in the United States is opposite to the response from shocks in Argentina because harvest in the two hemispheres occurs in different periods. In addition, the one-month lag between Brazilian and Argentine harvests may contribute to explain a turning point in the impulse-response function that occurs one month after the shock.

Production and characterisation of amorphous silica from rice husk waste

Rice covers about 1% of the earth’s surface. Rice husk is the major by-product of the riceprocessing industries which must be appropriately managed. On average 20% of the rice paddy is husk. The major constituents of rice husk are cellulose, lignin and silica. During growth, rice plants absorb silica and other minerals from the soil and accumulate it into their structures. Its composition varies with the diversity, climate and geographic location of growth. The high grade of silica in the husk opens a possibility for its valorisation. Through thermal treatment by calcination, with or without energy recovery, the ash obtained is constituted by amorphous silica with high porosity having potential application as ligand in construction materials, catalyst support, metals adsorbent, insulation or ceramics, among others. In the research developed, the rice husk was processed by washing, acid leaching and calcination in order to produce an ash, which was characterized aiming at assessing possible valorising solutions. The chemical treatment involved water washing for partial purification of the husk, and leaching with diluted sulphuric acid solution, allowing obtaining high metals removal efficiency, decreasing at least 90% of the initial content of contaminants (K, Fe and Mn). After calcination at 540ºC for organics decomposition, the final ash consisted in white colour amorphous silica as confirmed by XRPD analysis, being characterized by SEM to evaluate the microstructure. The results showed that after calcination the rice husk ash had a very porous, alveolar and even tracery morphology, which seems promising for applications requiring high reactivity, such as in construction materials and technical ceramics

Physical processing efficiency of saline vs. alkaline spent batteries

Physical processing of spent batteries which includes shredding and sieving operation is the first step for chemical treatment by hydrometallurgy. A laboratory study was carried out to evaluate physical processing efficiency, by analysing the resulting particle size, of alkaline and saline mignon-type Zn-MnO2 batteries. After shredding with a tip shredder, results obtained showed that alkaline batteries were more efficiently size reduced than saline batteries. Difference in particle size distribution was larger for granulometric fraction -20+11.2 mm and also higher for saline batteries. Average diameters (d50) for saline and alkaline batteries were respectively 9.1 and 6.2 mm. Chemical composition carried out on several granulometric fractions allowed to identify metals distribution through size categories. This analysis showed that zinc concentration with the grain size was almost constant, while manganese decreased when particle size increased. More than 95% of iron scarp from the battery cases had a particle size higher than 5.6 mm

Leaching behavior of several zinc rich residues in a hydrometallurgical recycling process

The leaching of metals contained in spent Zn-MnO2 batteries and electric arc furnace (EAF) dusts using sulfuric acid solutions was studied, in order to evaluate the feasibility of simultaneous treatment of both wastes by a hydrometallurgical process. In both residues, a substantial quantity of zinc was solubilized (about 100% in batteries and 70-80% in EAF dusts) in diluted acid solutions and room temperature, corresponding to the reaction of zinc oxide species. Other species were more refractory to the chemical attack, namely the manganese (III or IV) oxides in batteries and the zinc ferrite in dusts, requiring higher temperatures (e.g. 90ºC) and higher leachant concentrations. Lead present in EAF dusts was not solubilized in sulfate media, thus remaining in the leach residue. Results seem to confirm the possibility of treatment of both zinc-containing residues by the same hydrometallurgical process, eventually involving two leaching stages – diluted acid leaching and hot acid leaching – followed by solution purification through iron precipitation and Zn/Mn separation and recovery. Concerning lead, a second leaching circuit in chloride media could be developed for its potential recovery

Physical and chemical processing of printed circuit boards waste

A recycling process for PCB’s is being studied, based on physical processing and hydrometallurgical treatment. PCB’s waste was shredded in a lab cutting mill, resulting a grinded material with 90% (weight) with particle size less than 2.1 mm and an average particle diameter of 1.2 mm. Chemical analysis of granulometric fractions showed that the base metals like Cu, Zn, Pb and Sn concentrated mainly in intermediate size fractions (0.4-1.7 mm) being fines very rich in epoxy resin composite. About 80-90% of the principal metals were recovered in that size range. The first step of chemical treatment was the acid leaching of metals. The use of nitric acid solutions at appropriate conditions allowed the efficient solubilization of base metals like Cu, Ni, Zn, Pb and Ag. More than 90% recovery of Cu, Zn and Ni were achieved at 90ºC using 1 M HNO3. Dissolution of silver required higher concentrations (only 70% yield using 2 M HNO3). Tin leaching was inefficient in nitric media, being always lower than 20%. The leaching conditions here reported were adequate to the base metals solubilization, allowing further processing of leachates for separation and recovery using hydrometallurgical operations. Precious metals recovery would be attained in a subsequent leaching step using highly concentrated acidic solutions