Changes In Solids Concentration Research Articles

A real time in situ light-scattering technique for tailings solids content measurement: Near-infrared versus visible wavelengths

Optical scattering can be potentially used to develop an effective solids content measurement tool for tailings ponds monitoring and management. This bench-scale study investigated suitable laser wavelengths in both visible (405, 520 and 658 nm) and near infrared (980, 1310 and 1550 nm) ranges for real time in situ application in oil sands tailings. In general, the near infrared wavelengths demonstrated higher sensitivity over the entire test range compared to the visible wavelengths. Furthermore, residual bitumen in oil sands tailings tended to absorb the visible wavelengths, which interfered with the scattering light signals, leading to inaccurate measurements. Due to a sufficiently strong water absorption, the 1550 nm wavelength in particular showed an almost linear sensitivity of the light scattering with the change in solids concentration with a 1.5% accuracy and was able to overcome the effects of the variation in the physical and chemical properties of the samples including particle size distributions. Conveniently, the absorption was not strong enough to generate noise in the measurement caused by atmospheric moisture. The 1550 nm wavelength was identified as a promising candidate for the light scattering-based solids content analyzer for real time in situ tailings ponds monitoring. • Light scattering technique for real time in situ solids content measurement. • Investigate wavelengths from visible to near infrared. • 1550 nm wavelength demonstrated sensitivity to better than 2 percent level. • 1550 nm wavelength mitigates bitumen fouling effects in oil sands tailing applications.

TEMPERATURE AND CONCENTRATION EFFECTS OF OSMOTIC MEDIA ON OD PROFILES OF SWEET POTATO CUBES

A study was conducted to evaluate the effects of temperature and sucrose osmotic solution concentrations on osmotic dehydration profiles of sweet potato (Ipomea batata) cubes (3.5 cm sides). Two temperatures (26 and 50°C) and three concentrations (30:100, 50:100 and 70:100 w/w) were studied for various exposition times, up to 168 hours. Main influence was observed at higher temperature (50°C) due the fact that water loss (WL) and solids gains (SG) are faster and more intense. At 26°C no appreciable change in solids concentration was observed at distances deeper than 0.5 cm from the cubes surfaces even at 168 hours. At 50°C all the layers are affected even at shorter times (8 hours).

Ion Exchange and Surface Charge on Montmorillonite Clay

An ion‐exchange model originally developed for pure oxides prepared in the laboratory is extended to study of ion exchange and surface charge on a naturally occurring montmorillonite clay. The range of surface charges (−2.0 × 10−6 to 0 mol/m2) measured for montmorillonite with various electrolyte solutions and clay pretreatments is within the range of those measured for a wide variety of oxides prepared in the laboratory (−6.0 × 10−6 to 1.0 × 10−7 mol/m2), including MnO2‐IC1, MnO2‐IC12, MnO2‐IC22, titanium dioxide, ferric oxide, and aluminum oxide. In addition, fitted parameter values for lateral interaction constants and equilibrium constants for the acid sites that characterize ion exchange on montmorillonite are on the same order of magnitude as those obtained for pure oxides. Surface charge of montmorillonite in sodium nitrate solution is measured to be approximately 15 to 25% greater than that measured between a pH of 4 and 9 in calcium chloride solution. This difference is attributed to the greater charge on the calcium (2+) ion; thus, its stronger electrostatic attraction to the acid hydroxyl site. An order of magnitude change in solids concentration (Cp) can lead to a difference in measured net surface charge density of the same oxide sample of several orders of magnitude. This difference increases at higher pH, indicating the importance of reporting the corresponding Cp at which experiments are conducted.

Evaluation of the partitioning of hydrophobic pollutants between aquatic and solid phases in natural systems

Sorption partition coefficients are commonly used to quantify the distribution of organic pollutants between the aqueous and particulate phase of natural aqueous systems. Lotse et al. [6] found a significant increase in partitioning as the solid concentration decreases. Pollutants with larger partition coefficients have a more pronounced effect on the observed partitioning with changes in solid concentration. In the present study, partition coefficients for sediment-water systems were determined using Second Songhua River sediment. The effect of added DOC (using 12.5 ppm fulvic acid) and centrifuge speed on the partitioning of pollutants were studied. Dissolved organic carbon (DOC), nonsettling micro-particles (NSPs) and light absorption were also analyzed. From the results, the solids effect can be attributed to a transfer of solute-binding material from the solid phase to the liquid phase during the course of the partitioning procedure. This material, whether DOC or NSPs in nature, was not removed from the liquid phase during the separation procedure and possessed a higher capacity for the solute than the water itself. It increases the amount of solute in the liquid phase and makes the observed partition coefficients decrease. The true partition coefficients ( K oc t) of 11 constituents have been calculated from the observed partition coefficients at different solid concentrations. The values of K oc t approach a constant and cannot be affected by the solid concentration. It supports the explanation describing the effect of solids.