Berezniak, A. ; Ben-Gal, A. ; Mishael, Y. G. ; Nachshon, U. .
Manipulation Of Soil Texture To Remove Salts From A Drip-Irrigated Root Zone.
Vadose Zone Journal 2018,
17.
Publisher's VersionAbstractDrip irrigation is a useful method for the application of low-quality water because it does not wet the foliage and limits the spread of contaminants. Nevertheless, when using water containing high levels of dissolved salts, drip irrigation may be insufficient for leaching and can lead to soil salinization. A new conceptual model was tested experimentally and numerically to examine if manipulation of the distribution of soils with different textures could promote the removal of salts from the root zone and increase leaching efficiency. The manipulated root zone consisted of a volume of coarse soil, located under a drip irrigation emitter, surrounded by finer texture soil. We hypothesized that the differences in hydraulic properties between the two soils and the capillary barrier developed at their interface would generate a one-directional flow path of the salty water from the location of irrigation to the fine soil. This would enforce salt accumulation beyond the root zone. The concept was tested in a series of lysimeter and Hele–Shaw chamber experiments, together with a two-dimensional flow model created in HYDRUS-2D. Results showed preferential salt accumulation beyond the coarse segment of the manipulated soil, providing a volume of leached soil sufficient to support a healthy root system. Under conditions of homogenous soil texture, a notable buildup of salinity was observed in the central root zone, whereas under the manipulated texture conditions, such salt buildup was not observed.
Shabtai, I. A. ; Mishael, Y. G. .
Polycyclodextrin&Ndash;Clay Composites: Regenerable Dual-Site Sorbents For Bisphenol A Removal From Treated Wastewater.
ACS Applied Materials & Interfaces 2018,
10, 27088 - 27097.
Publisher's VersionAbstractThe greatest challenge of wastewater treatment is the removal of trace concentrations of persistent micropollutants in the presence of the high concentration of effluent organic matter (EfOM). Micropollutant removal by sorbents is a common practice, but sorbent employment is often limited because of fouling induced by EfOM and challenging sorbent regeneration. We directly addressed these two issues by designing regenerable dual-site composite sorbents based on polymerized β-cyclodextrin, modified with a cationic group (pCD+) and adsorbed to montmorillonite (pCD+-MMT). This dual-site composite was tailored to simultaneously target an emerging micropollutant, bisphenol A (BPA), through inclusion in β-cyclodextrin cavities and target anionic EfOM compounds, through electrostatic interactions. The removal of BPA from treated wastewater by the composite was not compromised despite the high removal of EfOM. The composites outperformed many recently reported sorbents. Differences in composite performance was discussed in terms of their structures, as characterized with TGA, XRD, BET and SEM. The simultaneous filtration of BPA and EfOM from wastewater by pCD+-MMT columns was demonstrated. Furthermore, successful in-column regeneration was obtained by selectively eluting EfOM and BPA, with brine and alkaline solutions, respectively. Finally, the composites removed trace concentrations of numerous high priority micropollutants from treated wastewater more efficiently than commercial activated carbon. This study highlights the potential to design novel dual-site composites as selective and regenerable sorbents for advanced wastewater treatment.The greatest challenge of wastewater treatment is the removal of trace concentrations of persistent micropollutants in the presence of the high concentration of effluent organic matter (EfOM). Micropollutant removal by sorbents is a common practice, but sorbent employment is often limited because of fouling induced by EfOM and challenging sorbent regeneration. We directly addressed these two issues by designing regenerable dual-site composite sorbents based on polymerized β-cyclodextrin, modified with a cationic group (pCD+) and adsorbed to montmorillonite (pCD+-MMT). This dual-site composite was tailored to simultaneously target an emerging micropollutant, bisphenol A (BPA), through inclusion in β-cyclodextrin cavities and target anionic EfOM compounds, through electrostatic interactions. The removal of BPA from treated wastewater by the composite was not compromised despite the high removal of EfOM. The composites outperformed many recently reported sorbents. Differences in composite performance was discussed in terms of their structures, as characterized with TGA, XRD, BET and SEM. The simultaneous filtration of BPA and EfOM from wastewater by pCD+-MMT columns was demonstrated. Furthermore, successful in-column regeneration was obtained by selectively eluting EfOM and BPA, with brine and alkaline solutions, respectively. Finally, the composites removed trace concentrations of numerous high priority micropollutants from treated wastewater more efficiently than commercial activated carbon. This study highlights the potential to design novel dual-site composites as selective and regenerable sorbents for advanced wastewater treatment.
Gardi, I. ; Mishael, Y. G. .
Designing A Regenerable Stimuli-Responsive Grafted Polymer-Clay Sorbent For Filtration Of Water Pollutants.
Science and Technology of Advanced Materials 2018,
19, 588 - 598.
Publisher's VersionAbstractABSTRACTA novel, stimuli-responsive composite, based on poly(4-vinylpyridine) (PVP) brushes, end-grafted to montmorillonite clay (GPC), was designed as a regenerable sorbent for efficient removal of pollutants from water. We characterized the novel composite sorbent and its response to pH, employing Fourier transform infrared, X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetry analysis and zeta potential measurements. In comparison with conventional, electrostatically adsorbed PVP composites (APC), the GPC presented superior characteristics: higher polymer loading without polymer release, higher zeta potential and lower pH/charge dependency. These superior characteristics explained the significantly higher removal of organic and inorganic anionic pollutants by this composite, in comparison with the removal by APC and by many reported sorbents. For example, the filtration (20 pore volumes) of selenate by GPC, APC and a commercial resin column was complete (100%), negligible (0%) and reached 90% removal, respectively. At low?moderate pH, the grafted polymer undergoes protonation, promoting pollutant adsorption, whereas at high pH, the polymer deprotonates, promoting pollutant desorption. Indeed, ?in-column? regeneration of the GPC sorbents was achieved by increasing pH, and upon a second filtration cycle, no reduction in filter capacity was observed. These findings suggest the possible applicability of this stimuli-responsive sorbent for water treatment.