Some barriers to the use of materials recovered from municipal solid waste
Abstract Municipal solid waste (MSW) contains materials which could be put to good use, yet it continues to be discarded, which suggests that it contains little or nothing of value under current conditions. This paper discusses the technical reasons for the lack of commercial interest in recovering materials from MSW. After examining the nature of the salvage industry and trends in the use of materials, the paper considers the characteristics of secondary materials, the properties required of them, and the scope for increased salvage activity. The market prospects are described for waste paper, ferrous and non- ferrous scrap, glass and polymers.
The influence of tin content on the reuse of magnetic metals recovered from municipal solid waste
Abstract The magnetically recoverable fraction of municipal solid waste (MSW magnetics) contains a large percentage of tinplate steel cans and, therefore, significant tin content. For areas where detinning is not readily available, this tin content is recognized as a potential barrier to the use of MSW magnetics in iron and steel production. Published reports on the effects of tin in iron and steel are reviewed. Tin is usually reported to harden steel, increase yield and tensile strength and decrease ductility and toughness, but the quantitative effects of tin have not been well defined. Reported tin levels in MSW magnetics are presented and a geometrical progression model for calculating tin residual buildup after repeated recycling is described. Based on tolerances for tin, a hierarchy of potential uses for MSW magnetics is proposed On a national scale, tin, by itself, would not present a barrier to reuse of recovered magnetics but this is not necessarily so on a local scale. Some steel plants, because of the types of products made, may not be able to reuse any MSW magnetics. Technological approaches to removing tin or reducing its effects are discussed.
Inhibition of Mild Steel Corrosion Using L-tryptophan and Synergistic Surfactant Additives
The corrosion inhibition characteristics of nitrogen containing amino acid L-tryptophan on mild steel in 0.1 M HCl solution, in the temperature range of 30-50 o C, was studied by weight loss and potentiodynamic polarization measurements. L-tryptophan significantly reduces the corrosion rates of mild steel; the maximum inhibition efficiency being 83% at 50 o C in presence of inhibitor concentration of 500 ppm. The effect of the addition of very small concentrations of anionic surfactant, sodium dodecyl sulfate (SDS), and of cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), on the corrosion inhibition behavior of L-tryptophan was also studied. The inhibition efficiency (IE) of L-tryptophan significantly improved in presence of both surfactants. The effect of SDS and CTAB on the corrosion inhibition behavior of L-tryptophan appears to be synergistic in nature, the values of synergism parameter being greater than unity. The adsorption of inhibitors on mild steel surface obeyed Langmuir’s adsorption isotherm. The calculated thermodynamic parameters for adsorption reveal a strong interaction between the inhibitors and the mild steel surface. The results obtained by electrochemical studies are consistent with the results of the weight loss measurements. L-tryptophan acts more anodic than cathodic inhibitor.