Variation of Al species during water treatment: correlation with treatment efficiency under varied hydraulic conditions

The concentration of hydrolyzed coagulant ion species is a key factor in determining drinking water treatment efficiency. Direct correlation of water treatment efficiency with changes in species during coagulation has not been addressed. We investigated the correlation under different hydraulic conditions and water treatment efficiencies including changes in removal of turbidity, ultraviolet adsorption at 254 nm (UV254) and dissolved organic carbon (DOC). Results highlighted that Al species (monomeric species as Ala, medium polymeric species as Alb and colloidal species as Alc) behaved differently during coagulation and treatment efficiencies were affected. When varying the mixing speed, the removal of Alc species had a strong negative correlation with water treatment efficiency but under other hydraulic conditions positive correlations were found. The removal of Ala species was positively correlated with water treatment efficiency, but under other hydraulic conditions the low abundance of Ala species meant the correlation was difficult to observe. The Alb species were significantly and positively correlated with water treatment efficiency with the highest correlation coefficient (R2) of 0.87. The correlation of metallic species with removal efficiencies of the DOC and the UV254 produced higher R2 values. Correlation of the rate of removal of Alb species with the removal efficiencies of the DOC or the UV254 was better than for Alc.

Opto-Thermophoretic Tweezers and Assembly

Opto-thermophoretic manipulation is an emerging field, which exploits the thermophoretic migration of particles and colloidal species under a light-controlled temperature gradient field. The entropically favorable photon–phonon conversion and widely applicable heat-directed migration make it promising for low-power manipulation of variable particles in different fluidic environments. By exploiting an optothermal substrate, versatile opto-thermophoretic manipulation of colloidal particles and biological objects can be achieved via optical heating. In this paper, we summarize the working principles, concepts, and applications of the recently developed opto-thermophoretic techniques. Opto-thermophoretic trapping, tweezing, assembly, and printing of colloidal particles and biological objects are discussed thoroughly. With their low-power operation, simple optics, and diverse functionalities, opto-thermophoretic manipulation techniques will offer great opportunities in materials science, nanomanufacturing, life sciences, colloidal science, and nanomedicine.

Solubilities and solubility products of thorium hydroxide under moderate temperature conditions

The Th solubilities of the sample solutions that initially contained Th(OH)4(am) prepared by undersaturation and oversaturation methods in the pHcrange of 2.0–8.0 in a 0.5 M ionic strength solution of NaClO4and HClO4and stored at aging temperatures (Ta) of 298, 313 and 333 K were investigated in this study. After a certain period of time up to 40 weeks depending onTa, supernatants of the sample solutions were ultrafiltrated through 3 kDa membranes under the measurement temperature (Tm) of 298, 313 and 333 K. Size distributions of the colloidal species were investigated by ultrafiltration using membranes with different pore sizes ranging from 3 to 100 kDa, and the solid phases were examined by X-ray diffraction (XRD). The solubility of the sample solutions obtained after aging atTa=298 K using undersaturation method with continuous shaking was similar to those of dried precipitate of Th hydroxide. The solubilities obtained after aging atTa=313 and 333 K were lower than those atTa=298 K. The XRD spectra suggested that the crystallization of the solid phase proceeded under these elevated temperatures. The solubility of the sample solutions obtained after aging atTa=333 K using the oversaturation technique were similar to those prepared by undersaturation method and aged at the sameTa. A slight temperature dependence of the apparent solubilities on theTmwas observed in the sample solutions prepared by both methods. The solubility products$({K_{{\text{sp,}}{T_{\text{a}}}}}({T_{\text{m}}}))$after differentTaandTmwere determined from the solubility analysis. The observed increase in the formation constant$({K_{{\text{s,}}{T_{\text{a}}}}}({T_{\text{m}}}))$of Th4++(4+x)H2O(1)⇌Th(OH)4·xH2O(s,Ta)+4H+with increasingTmindicated that the reaction was endothermic. The enthalpy change$(\Delta_{r}H_{m\_ T_{\text{a}} \to {\text{cr}}}^{\circ} )$between the solid phases of Th(OH)4·xH2O(s,Ta) and ThO2(cr) suggested that the solid phase transformation from Th(OH)4·xH2O(s,Ta) to ThO2(cr) contains an endothermic process.

Uranium Dissolution and Geochemical Modeling in Anoxic and Oxic Solutions

ABSTRACTHigh Level Waste (HLW) glasses are to be stored in deep geologic repositories around the world. Some potential repository geologies have oxidizing groundwaters while some have reducing or anoxic groundwaters. The differences in the oxidizing potential of the groundwater, expressed as groundwater Eh, which has a profound impact on the release of multivalent species such as iron and uranium from the glass. Static leach testing of monolithic glass samples (ASTM C1220) doped with uranium were performed at 90°C in an Ar glovebox under anoxic and oxic conditions. Tests were performed in both deionized water and in simulated basaltic groundwater that was pre-equilibrated at low Eh. Geochemical modeling of the measured Eh-pH conditions from the oxic and anoxic experiments using Geochemist’s Workbench software, suggested that different colloidal species control the release of uranium species under oxic and anoxic conditions.

Light Sensitized Disinfection with Fullerene

Fullerene has drawn wide interest across many fields due to its favorable electronic and optical properties, which has spurred its use in a myriad of applications. One of the hallmark properties of fullerene is its ability to act as a photosensitizer and efficiently generate 1O2, a form of Reactive Oxygen Species (ROS), upon visible irradiation when dispersed in organic solvents. However, the application of fullerene in environmental systems has been somewhat limited due to fullerene's poor solubility in water, which causes individual fullerene molecules to aggregate and form large colloidal species, quenching much of fullerene's 1O2 production. This is unfortunate given that 1O2 provides many advantages as an oxidant compared to ROS produced from typical advanced oxidation processes, such as OH radicals, due to 1O2's greater chemical selectivity and its ability to remain unaffected by the presence of background water constituents, such as natural organic matter and carbonate. Hence, fullerene materials may hold great potential for the oxidation and disinfection of complex waters. Herein, we chronicle the advances that have been made to propel fullerene materials towards use in emerging water disinfection technologies. Two approaches to overcome fullerene aggregation and the subsequent loss of 1O2 production in aqueous systems are herein outlined: 1) addition of hydrophilic functionality to fullerene's cage, creating highly photoactive colloidal fullerenes; and 2) covalent attachment of fullerene to solid supports, which physically prevents fullerene aggregation and allows efficient 1O2 photo-generation. An emphasis is placed on the inactivation of MS2 bacteriophage, a model for human enteric viruses, highlighting the potential of fullerene materials for light-activated disinfection technologies.

Towards better understanding of C60organosols

The C60colloidal species in acetonitrile are negatively charged owing to formation of anion-radicals. Electrolytes coagulate the organosol, and multi-charged cations cause the re-charging of the particles.