Application of riverbed sand for the adsorptive separation of cadmium(II) from aqueous solutions has been investigated. Removal increased from 26.8 to 56.4% by decreasing the initial concentration of cadmium from 7.5 x 10-5 to 1.0 x 10-5 M at pH 6.5, 25 °C temperature, agitation speed of 100 rpm, 100 μm particle size and 1.0 x 10-2 NaClO4 ionic strength. Process of separation is governed by first order rate kinetics. The value of rate constant of adsorption, kad, was found to be 2.30 x 10-2 per min at 25 °C. Values of coefficient of mass transfer, βL, were calculated and its value at 25 °C was found to be 1.92 x 10-2 cm/s. Values of Langmuir constant were calculated. Values of thermodynamic parameters ΔG0, ΔH0 and ΔS0 were also calculated and were recorded as -0.81 kcal/mol, -9.31 kcal/mol and -28.10 cal/mol at 25 °C. pH has been found to affect the removal of cadmium significantly and maximum removal, 58.4%, has been found at pH 8.5. Process can be used for treatment of cadmium(II) rich wastewaters.

Plant uptake is a major pathway by which toxic metals can enter the food chain. In this laboratory study we grew spinach, radish, and perennial ryegrass on sand blends containing 50% waste foundry sand (WFS) to assess the availability of Al, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, V, and Zn. The WFSs utilized in this study were from aluminum, iron, and steel foundries. Although there were differences in the amounts of metals accumulated by the various plant species, excessive amounts of heavy metals were not taken up, regardless of WFS treatment. In spinach and radish, B, Cu, Fe, Mn and Zn were found to be within or close to the sufficiency range for agronomic crops. In ryegrass cuttings at 27, 57, and 87 days, Cu and Zn were within sufficiency ranges, but plants were Fe deficient and contained elevated concentrations of B, Mn, and Mo. Data from this study will be useful for state regulatory agencies interested in developing beneficial use regulations for WFSs.

This paper reports the effect of using coarse substrates in the upper layer of a gravel-based tidal flow reed bed treating pig farm wastewater. The aim of this unconventional medium arrangement is to seek a solution for the problem of clogging that frequently takes place during the treatment of strong wastewaters. Results from lab-scale experiments demonstrated that, in general, employing coarse substrates in the upper layer of the reed bed gave greater efficiency for the removal of organic matter and suspended solids, due to reduced clogging. A specific clogging tendency rate was defined to quantitatively describe the clogging behaviour. Calculation of the tendency rate revealed that the unconventional medium arrangement had a clear advantage over the conventional arrangement of employing fine gravel or sand in top layer.

Anion exchange membrane (AEM), Nafion® tubing, and strong anion exchange cartridges (SAX) were evaluated as passive sampling devices for perchlorate uptake in soybean (Glycine max). Plant uptake studies and AEM studies were conducted in three soil textures: Ottawa sand, silt loam soil, and sandy loam soil. Nafion® tubing and SAX experiments were only conducted in Ottawa sand. AEMs were sampled every hour for the first 12 h, then every 12 h until 72 h. Perchlorate concentrations in plant tissues, SAX, and water solution in Nafion® tubing were determined weekly for 4 weeks. In sand, the amount of perchlorate accumulated in AEM increased linearly with time. Perchlorate uptake by soybean plants was poorly described by linear regressions with perchlorate concentrations on membranes. The only significant relationship between soybean uptake and membrane uptake occurred for data from membranes buried 6–12 h in sand. Significant differences (p < 0.0001) were observed for the amount of perchlorate exchanged on AEM in the three soil textures. There were no differences in perchlorate concentrations in soybean leaves among the three soil textures. Regression analysis of perchlorate concentrations in water within Nafion® tubing and in sand solution indicted that there was a significant linear relationship between them (r ² = 0.5132, p = 0.0006). Perchlorate was not detected in eluent of SAX. AEM demonstrated its potential to accumulate perchlorate. Nafion® tubing is not a good surrogate for plant uptake, but may be a promising PSD for soil solution. SAX may not be used as a PSD by itself.