Treatment of cyanide effluents by oxidation and adsorption in batch and column studies.

In this study the removal of free cyanide from aqueous solutions by air oxidation and adsorption was investigated. Effects of air and pure oxygen, and catalyst on the rate and extent of the removal of cyanide were studied. It was found that the oxidative removal of cyanide by air/oxygen was very limited although it tended to improve in the presence of pure oxygen and catalyst such as activated carbon (AC) and copper sulphate. In the presence of continuous aeration, the non-oxidative removal of cyanide was correlated with a decrease in pH effected apparently by the transfer of carbon dioxide from air phase into the medium. The removal of cyanide by adsorption on activated carbon, nut shell (NS) and rice husk (RH) was also examined. Adsorption capacity of activated carbon was shown to be significantly enhanced via impregnation of activated carbons with metals such as copper (AC-Cu) and silver (AC-Ag). In the column tests, the breakthrough capacity of adsorbents was found to be in an increasing order of RH

Potential use of pyrite cinders as raw material in cement production: results of industrial scale trial operations.

Pyrite cinders, which are the waste products of sulphuric acid manufacturing plants, contain hazardous heavy metals with potential environmental risks for disposal. In this study, the potential use of pyrite cinders (PyCs) as iron source in the production of Portland cement clinker was demonstrated at the industrial scale. The chemical and mineralogical analyses of the PyC sample used in this study have revealed that it is essentially a suitable raw material for use as iron source since it contains >87% Fe(2)O(3) mainly in the form of hematite (Fe(2)O(3)) and magnetite (Fe(3)O(4)). The samples of the clinkers produced from PyC in the industrial scale trial operation of 6 months were tested for the conformity of their chemical composition and the physico-mechanical performance of the resultant cement products. The data were compared with the clinker products of the iron ore, which is used as the raw material for the production Portland cement clinker in the plant. The chemical compositions of all the clinker products of PyC appeared to conform to those of the iron ore clinker, and hence, a Portland cement clinker. The mechanical performance of the mortars prepared from the PyC clinker was found to be consistent with those of the industrial cements e.g. CEM I type cements. It can be inferred from the leachability tests (TCLP and SPLP) that PyC could be a potential source of heavy metal pollution while the mortar samples obtained from the PyC clinkers present no environmental problems. These findings suggest that the waste pyrite cinders can be readily used as iron source for the production of Portland cement. The availability of PyC in large quantities at low cost provides further significant benefits for the management/environmental practices of these wastes and for the reduction of mining and processing costs of cement raw materials.

Medicaid expansions and the crowding out of private health insurance among children.

This paper re-examines the magnitude of crowd out among children. We use longitudinal data that allow us to identify and differentiate groups of children based on whether their eligibility for Medicaid was affected by the program's eligibility expansions. We investigate whether changes in insurance coverage of children affected by the expansions differed from changes in insurance coverage of children unaffected by the expansions. For example, we directly measure whether there was a greater decrease in private insurance coverage among children who became eligible for Medicaid than among children whose eligibility was unaffected. Our results suggest that there was relatively little crowd out among children. We estimate that 18.9% of the recent increase in Medicaid enrollment came from private insurance.