Steel slag quality control for road construction aggregates and its environmental impact: case study of Vietnamese steel industry—leaching of heavy metals from steel-making slag

Environmental Science and Pollution Research - Steel slag is an industrial by product of steel manufacturing processes and has been widely utilized within civil and construction materials for road...     

Thermal remediation of PCDD/Fs contaminated soil by zone combustion process

A new thermal process has been proposed for remediating soils contaminated by chlorinated organic compounds, e.g., PCDD/Fs and PCBs. This is to apply the "zone combustion process" which utilizes stable combustion of coke particles in the packed bed to soils with air flow across the bed. The usefulness and validity were obtained the results showing that more than 98.9% of PCDD/Fs in the soil was successfully removed in a laboratory-scale experiment. Some pretreatment of the soil sample, such as drying, pre-granulation and addition of limestone was found to make the removal efficiency better. Although, some fundamentals on the behavior of PCDD/Fs, e.g., decomposition/vaporization ratios and formation of other compounds cannot be certainly identified yet, the present results clearly show a way to remediate the contaminated soils and solid wastes.     

Removal of mercury using processes involving sulfuric acid during zinc production in an imperial smelting process (ISP) plant

Journal of Material Cycles and Waste Management - Mercury emissions from non-ferrous metal industries are a major environmental concern. Because of the large differences in mercury emission factors...     

Phosphate recovery from phosphorus-rich solution obtained from chicken manure incineration ash

The recovery of phosphorus from waste is very important for Japan because Japan has no natural phosphorus resources. In order to recover phosphorus from incineration ash of chicken manure, an acid dissolution–alkali precipitation method was investigated. Phosphorus content in the ash was 8%. The ash was treated with hydrochloric acid to obtain phosphorus-rich solution. Phosphorus could then be recovered as a precipitant by adding sodium hydroxide solution into the phosphorus-rich solution and gradually changing the pH in the solution to 3, 4, and 8. At pH 3, a small amount of phosphorus was precipitated to remove iron, which would cause coloring of subsequent precipitants. At pH 4, 84% of the phosphorus in the original solution could be recovered as CaHPO₄ · 2H₂O with a purity of 92%. At pH 8, 8% of the phosphorus in the phosphorus-rich solution could be recovered as identified hydroxyapatite. A recovery rate of 92% phosphorus as CaHPO₄ · 2H₂O and identified as hydroxyapatite was achieved.     

Batch separation of shredded bulky waste by gas-solid fluidized bed at laboratory scale

A gas-solid fluidized bed separator using various bed materials was used to separate shredded municipal bulky waste (SBW). Using 290 microm glass beads as the bed material, the apparent density of the fluidized bed was 1.5 g/cm(3) and the SBW could be separated into combustibles such as wood, paper and plastics and incombustibles such as metals and glass. The overall efficiency (Newton's efficiency) of the separation was calculated to be 0.93. In order to obtain high efficiency, the superficial velocity must be adjusted so that the fluidized bed is agitated moderately and at the same time there is no weak fluidized region. Using a mixture of particles of nylon shot and 68 microm glass beads, the apparent density of the fluidized mixture bed could be varied between 0.63 and 0.99 g/cm(3) by changing the mixing ratio of the two materials. In the case of a mixing ratio of 20% for glass beads, an apparent density of 0.65 g/cm(3) was produced, in which wood and paper components were recovered while plastics remained in the bed to give a final overall efficiency of 0.88.     

Leaching behavior and mineral speciation of cement-solidified boiler fly ash from industrial waste incineration containing waste tires

Journal of Material Cycles and Waste Management - This study characterizes the leaching behavior of fuel raw boiler fly ash (BFA) and cement-solidified/stabilized raw boiler fly ash (SBFA). X-ray...     

Mechanical properties of steel slag replaced mineral aggregate for road base/sub-base application based Vietnam and Japan standard

Steelmaking slag is one of the most massive industrial by-products generated during steelmaking processes. This paper presents the current steelmaking slag production status and its potential to use as mineral aggregates in base/sub-base layer of road pavement. The mechanical properties of steelmaking slag were confirmed by the test method specified in Vietnam specification. The volume stability test of the slag was conducted based on JIS A 5015-2018 (Japanese Industrial Standard: Iron and steel slag for road construction). From the results, it was confirmed that steelmaking slag can satisfy all the mechanical requirements specified in Vietnam specification and the requirements regarding stability specified in JIS A 5015-2018. In addition, it was found that the elastic modulus of steelmaking slag applied as a base or sub-base layer in pavement was higher than that of the conventional graded aggregate made from mineral aggregate. Therefore, the thickness of pavement can be reduced by using steelmaking slag, and the construction cost can be lower.