Transport of hexavalent chromium in the vadose zone by capillary and evaporative transport from chromium ore processing residue

2016 ◽  
Vol 53 (4) ◽  
pp. 619-633 ◽  
Author(s):  
Katrina Rhoades ◽  
Jongwan Eun ◽  
James M. Tinjum
Keyword(s):  
Vadose Zone ◽  
Capillary Rise ◽  
Small Diameter ◽  
Silty Sand ◽  
Column Tests ◽  
Chromium Ore ◽  
Ore Processing ◽  
Containment Strategy ◽  
Precipitation Events ◽  
Surface Background

Column tests were conducted to evaluate the transport of Cr from underlying chromium ore processing residue (COPR) through the vadose zone in capped and uncapped scenarios and to determine if an asphalt cover system is a viable containment strategy. Four large (140 mm diameter) columns and one small (50 mm diameter) column were filled with COPR underlying a silty sand. Wet–dry cycling (representing precipitation events) induced suction gradients in the uncapped columns. At termination, the uncapped columns contained 10–120 mg/kg Cr on the surface (background Cr level, 8.3 mg/kg), and the capped columns had Cr concentrations equal to background levels, indicating that the capped surface limited Cr migration to the surface. The smaller column was constructed to study the evaporative transport of Cr by simulating a heat source (i.e., sunshine) to increase suction. Soil specimens from the surface of the small-diameter, uncapped column were as high as 410 mg/kg Cr(VI) after 4 weeks. A series of numerical analyses was conducted to interpret and validate the experimental results and to quantify Cr(VI) transport through composite asphalt caps. Through column testing and numerical analysis, in a controlled condition, Cr was found to migrate from COPR in the vadose zone by evaporation and capillary rise, but a controlled, capped condition effectively limited Cr migration.

scholarly journals Complete Reduction of Hazardous Cr(VI) in Chromium Ore Processing Residue Dump Site

2018 ◽  
Vol 30 (3) ◽  
pp. 620-624 ◽  
Author(s):  
Vanitha Murugaiyan ◽  
T. Sehar ◽  
S. Selvaraj ◽  
P. Kamatchi Selvaraj
Keyword(s):  
Dump Site ◽  
Complete Reduction ◽  
Chromium Ore ◽  
Ore Processing

Fluid migration in the vadose zone from 3-D inversion of resistivity monitoring data

Geophysics ◽  
1998 ◽  
Vol 63 (1) ◽  
pp. 41-51 ◽  
Author(s):  
Stephen Park
Keyword(s):  
Vadose Zone ◽  
Fluid Migration ◽  
Inversion Process ◽  
Resistivity Tomography ◽  
Capillary Action ◽  
Fine Grained ◽  
Fluid Concentration ◽  
Resistivity Inversion ◽  
Systematic Development ◽  
Precipitation Events

The movement of a small plume of fresh water through the vadose zone was monitored using surface resistivity tomography and pole‐pole potential measurements. Sets of potential measurements on a square grid at several times throughout the experiment show gradual, progressive, and systematic development of low‐resistivity zones that are inferred to be loci of fluid concentration. A procedure for inverting percentage changes in potentials is developed here and used to map maximum potential changes of 13% into resistivity decreases of up to 40% through 3-D resistivity inversion. The resulting patterns are complex, with both resistivity increases and decreases needed to match the observed data. The resistivity reductions show a spatial connection to the plume’s source and are suggestive of the fluid migration. Resistivity increases generally appear to form rims surrounding the decreases and may be artifacts of the inversion process. However, some isolated increases in the surface layer may be caused by evaporation of fluid from previous precipitation events. Interpretation of the complex patterns may limit the usefulness of this method for monitoring fluid migration. Nonetheless, the resulting pattern of resistivity reductions may show details of fluid migration that are unavailable with more conventional monitoring techniques. In this experiment, comparison of the volume with reduced resistivity with the volume of injected water predicts only a 0.5% increase in saturated porosity, demonstrating that fluid flow in the vadose zone was most likely controlled by the distribution of fine‐grained clays and silts and occurred by capillary action.

Optimisation of metal extraction from chromium ore processing residue in New Jersey, USA

2018 ◽  
Vol 13 (4) ◽  
pp. 98-107
Author(s):  
Wiwat Kamolpornwijit ◽  
Jay N Meegoda ◽  
Janitha H Batagoda
Keyword(s):  
New Jersey ◽  
Metal Extraction ◽  
Chromium Ore ◽  
Ore Processing

Specific Gravity of Expansive Chromium Ore Processing Residue with Complex Microstructure

2010 ◽  
Vol 33 (4) ◽  
pp. 102836 ◽  
Author(s):  
L. D. Suits ◽  
T. C. Sheahan ◽  
Andrew M. Millspaugh ◽  
James M. Tinjum ◽  
Timothy A. Boecher
Keyword(s):  
Specific Gravity ◽  
Chromium Ore ◽  
Ore Processing

Preventing surface deposition of chromium with asphalt caps at chromite ore processing residue sites: a case study

2007 ◽  
Vol 44 (7) ◽  
pp. 814-839 ◽  
Author(s):  
Karen S Henry ◽  
John C Petura ◽  
Steven Brooks ◽  
Steven Dentico ◽  
Stephen A Kessel ◽  
...  
Keyword(s):  
Hexavalent Chromium ◽  
Capillary Rise ◽  
Matric Suction ◽  
Upward Movement ◽  
Chromite Ore Processing Residue ◽  
Chromite Ore ◽  
Ore Processing ◽  
Unsaturated Hydraulic Conductivity ◽  
Water Rise

Caps were constructed on chromite ore processing residue (COPR) sites in the Kearny, New Jersey, area between 1989 and 1994 to prevent human exposure to hexavalent chromium (Cr(VI)). The caps comprise geotextile overlain by 100 mm of dense graded aggregate (DGA) and 100 mm of hot mix asphalt (HMA). Prior to constructing these "composite asphalt caps" (CACs), Cr(VI) was sometimes deposited on surface soils as chromate (salts) during evaporative periods. We initially thought the geotextile and DGA acted as a capillary barrier, stopping capillary water rise, but site inspection revealed that the DGA and geotextile were too moist to perform this function. Further study included a literature review, DGA capillary rise estimates, in situ measurement of soil-water content over 7 months at a representative COPR site, and numerical modeling of matric suction gradients induced by evaporation. The collective results reveal that the CACs eliminate upward matric suction gradients from the COPR–soil through the DGA, thereby precluding surface chromate deposition. Even during evaporative periods, the low unsaturated hydraulic conductivity of the HMA restricts upward movement of moisture and soluble chromate from underlying COPR–soil. In contrast, there are almost always upward matric suction gradients in uncapped COPR–soil.Key words: capillary rise, chromite ore processing residue, chromate, hexavalent chromium, composite asphalt cap, evaporation.

scholarly journals Adsorption Characteristics and Transport Behavior of Cr(VI) in Shallow Aquifers Surrounding a Chromium Ore Processing Residue (COPR) Dumpsite

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Yu Liu ◽  
Yin Li ◽  
Yucheng Hu ◽  
Khan M. G. Mostofa ◽  
Siliang Li ◽  
...  
Keyword(s):  
Shallow Aquifer ◽  
Column Experiments ◽  
Silty Clay ◽  
Shallow Aquifers ◽  
Adsorption Characteristics ◽  
Comprehensive Management ◽  
Chromium Ore ◽  
Transport Behavior ◽  
Ore Processing ◽  
Pseudo Second Order

This study explored the stratigraphic distribution and soil/shallow aquifer characteristics surrounding a chromium ore processing residue (COPR) dumpsite at a former chemical factory in China. Total Cr levels in top soils (5–10 cm) nearby the COPR dumpsite were in the range of 8571.4–10711.4 mg/kg. Shallow aquifers (1–6 m) nearby the COPR dumpsite showed a maximum total Cr level of 9756.7 mg/kg. The concentrations of Cr(VI) in groundwater nearby the COPR dumpsite were 766.9–1347.5 mg/L. These results display that the top soils, shallow aquifers, and groundwater of the study site are severely polluted by Cr(VI). Then, three aquifers (silt, clay, and silty clay), respectively, collected from the depth of 1.4–2.4 m, 2.4–4.8 m, and 4.8–11.00 m were first used to evaluate the adsorption characteristics and transport behavior of Cr(VI) in shallow aquifers by both batch and column experiments. The adsorption of Cr(VI) on tested aquifers was well described by pseudo-second-order equation and Freundlich model. The adsorption capacities of Cr(VI) on three aquifers followed the order: clay > silty clay > silt. The kinetics proved that Cr(VI) is not easily adsorbed by the aquifer mediums but transports with groundwater. Thermodynamics indicated that Cr(VI) adsorption on tested aquifers was feasible, spontaneous, and endothermic. Cr(VI) adsorption on tested aquifers decreased with increasing pH. Furthermore, the transport of Cr(VI) in adsorption columns followed the sequence of clay < silty clay < silt. Desorption column experiments infer that the Cr(VI) adsorbed on aquifers will desorb and release into groundwater in the case of rainwater leaching. Therefore, a proper treatment of the COPR and a comprehensive management of soils are vital to prevent groundwater pollution.

Field Tests and Numerical Analyses of Subgrade Soil Reinforced with Grids of Stabilized Granular Columns

1996 ◽  
Vol 1534 (1) ◽  
pp. 72-79
Author(s):  
Evert C. Lawton ◽  
Anagha A. Mokashi ◽  
Nathaniel S. Fox
Keyword(s):  
Small Diameter ◽  
Field Tests ◽  
Reinforced Soil ◽  
Silty Sand ◽  
Silica Sand ◽  
Numerical Analyses ◽  
Triaxial Tests ◽  
Subgrade Soils ◽  
Subgrade Soil ◽  
Native Soil

Field tests and numerical analyses conducted to establish the feasibility of reinforcing soft, loose, or otherwise inadequate subgrade soils with a grid of small-diameter, stabilized, vertical granular columns to support traditional pavement systems are described. This technique may prove to be cost-effective if it is used to improve subgrade soils so that the sub-base or base courses can be reduced in thickness or eliminated. Field plate bearing tests were carried out on unreinforced cohesionless silty sand and on the same soil reinforced with vertical reinforcing columns constructed of four materials: crushed granitic gneiss, silica sand, cement-stabilized native soil, and cement-stabilized silica sand. The field tests indicated that the columns made of the two cement-stabilized materials substantially increased the subgrade modulus of the native soil. In contrast, the two unstabilized columnar reinforcing materials produced no substantial improvement in stiffness. The field tests were modeled by using an axisymmetric finite-element (FE) program and hyperbolic constitutive relationships for the native soil and the columnar reinforcing materials. Triaxial tests were performed on reconstituted specimens of the native soil and compacted specimens of cement-stabilized native soil to determine the stress–strain–strength parameters required for the FE analyses. The FE analyses modeled the plate bearing tests on the reinforced soil to a reasonable degree, indicating that the FE method used has the potential to simulate a complete pavement system (including a wearing surface) in which the subgrade soil is reinforced with columns of stabilized granular materials.

Conversion of Chromium Ore Processing Residue to Chrome Steel

2008 ◽  
Author(s):  
Jay N. Meegoda ◽  
Wiwat Kamolpornwijit ◽  
Zhengbo Hu ◽  
Robert Mueller ◽  
Ravi Patraju
Keyword(s):  
Chrome Steel ◽  
Chromium Ore ◽  
Ore Processing
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