Metal removal from soil leachates using DTPA-functionalised maghemite nanoparticles, a potential soil washing technology

There is significant current interest in the application of magnetic (magnetite or maghemite) nanoparticles functionalised with chelating agents for the environmental remediation of metal contaminated waters and solutions. Whilst there is a body of knowledge about the potential remediation efficacy of such engineered nanoparticles from studies involving synthetic solutions of single metals, there is relatively little data involving mixed-metal solutions and virtually no studies about nanoparticle performance in chemically complex environmental solutions representing those to which a scaled-up nanoremediation process might eventually be applied. Therefore, we investigated the ability of diethylenetriaminepentaacetic acid (DTPA)-functionalised, silica-coated maghemite nanoparticles to extract potentially toxic (Cd, Co, Cu) and "non-toxic" (Ca, Mg) metals from solution (initial [metal] = 10 mg L ; pH range: 2-8) and to extract a wider range of elements (As, Ca, Cd, Co, Cr, Cu, Mg, Na, Pb, Zn) from leachate obtained from 10 different contaminated soils with variable initial pH, (semi-)metal and dissolved organic carbon (DOC) concentrations. The functionalised nanoparticles could extract the potentially toxic metals with high efficiency (in general >70%) from single metal solutions and with efficiencies that were either unaffected or reduced from the soil leachates. K values remained high (>500 L kg ), even for the soil leachate extractions. Our findings show that DOC and relatively high concentrations of non-toxic elements do not necessarily reduce the efficiency of metal contaminant removal by DTPA-functionalised magnetic nanoparticles and thus demonstrate the remediation potential of such particles when added to chemically complex soil-derived contaminated solutions. [Abstract copyright: Copyright © 2018 Elsevier Ltd. All rights reserved.

Adsorption of Pb and Zn from binary metal solutions and in the presence of dissolved organic carbon by DTPA-functionalised, silica-coated magnetic nanoparticles

The ability of diethylenetriaminepentaacetic acid (DTPA)-functionalised, silica-coated magnetic nanoparticles to adsorb Pb and Zn from single and bi-metallic metal solutions and from solutions containing dissolved organic carbon was assessed. In all experiments 10 mL solutions containing 10 mg of nanoparticles were used. For single metal solutions (10 mg L-1 Pb or Zn) at pH 2 to 8, extraction efficiencies were typically >70%. In bi-metallic experiments, examining the effect of a background of either Zn or Pb (0.025 mmol L-1) on the adsorption of variable concentrations (0 - 0.045 mmol L-1) of the other metal (Pb or Zn, respectively) adsorption was well modelled by linear isotherms (R2>0.60; p≤0.001) and Pb was preferentially adsorbed relative to Zn. In dissolved organic carbon experiments, the presence of fulvic acid (0, 2.1 and 21 mg DOC L-1) reduced Pb and Zn adsorption from 0.01, 0.1 and 1.0 mmol L-1 solutions. However, even at 21 mg DOC L-1 fulvic acid, extraction efficiencies from 0.01 and 0.1 mmol L-1 solutions remained >80% (Pb) and > 50% (Zn). Decreases in extraction efficiency were significant between initial metal concentrations of 0.1 and 1.0 mmol L-1 indicating that at metal loadings between c. 100 mg kg-1 and 300 mg kg-1 occupancy of adsorption sites began to limit further adsorption. The nanoparticles have the potential to perform effectively as metal adsorbents in systems containing more than one metal and dissolved organic carbon at a range of pH values

Analysis of water absorption onto ceria and thoria thin films by direst mass and contact angle measurements:14th International Nuclear Fuel Cycle Conference, GLOBAL 2019 and Light Water Reactor Fuel Performance Conference, TOP FUEL 2019

Plutonium oxide (PuO2) is one of the most highly radioactive products of the nuclear fuel cycle and its storage poses particular challenges due to the high temperatures produced by its decay and the production of gases from, inter alia, surface adsorbed water entrained with the PuO2 during the packaging process. Its high radiotoxicity necessitates the use of actinide oxides in similar oxidation states, such as CeO2 and ThO2, as model systems to allow the comprehensive study of its interaction with water under storage conditions. We have developed a method which enables direct gravimetric measurement of the adsorption of microgram amounts of water onto CeO2 and ThO2 thin films, also with masses in the microgram range. Additionally sessile contact angles of water droplets deposited onto the same films have been measured to provide a correlating measure of the affinity of the oxide surface with water. Porous CeO2 and ThO2 films were deposited from a surfactant based precursor solution onto thin GaPO4 crystal and glass substrates. The absorption of water onto the CeO2 or ThO2 coating at different relative humidities was then studied in a closed reactor using crystal nanobalance gravimetry, wherein changes in crystal resonant frequency due to absorbed mass are directly and linearly related to mass changes occurring at the crystal surface. Using this method, we have determined the enthalpy of absorption of water onto CeO2 to be 49.7 kJmol-1 and onto ThO2 to be 54.6 kJmol-1 at 75°C, 11 and 15 kJmol-1 greater than the enthalpy of evaporation. Sessile contact angle measurements on the same films provide values for CeO2 and ThO2 of 56° and 27° respectively - indicating that water shows a greater affinity for the ThO2 surface than CeO2, an observation consistent with the hierarchy of water adsorption enthalpies derived here These enthalpies are within the range predicted for the reversible absorption of water onto PuO2, confirming this method allows for the investigation of water absorption onto plutonia using microgram samples. The significantly higher enthalpy of water absorption for thoria over ceria, and the correspondingly smaller water droplet contact angles indicates a high variation in water-absorbing properties of commonly used plutonia analogues, further emphasizing the need for studies on active PuO2 samples. Copyright © GLOBAL 2019 - International Nuclear Fuel Cycle Conference and TOP FUEL 2019 - Light Water Reactor Fuel Performance Conference.All rights reserved

A distributed fuzzy logic controller for a prosthetic hand / Mohd Yazed Ahmad

A Fuzzy Logic with distributed control monitoring (D S) sy tern i implemented to control multiple degree-of-freedom (DOF) prosthetic fingers. Ther are four fingers with 3-DOF and a thumb with 4-DOF. Five identical microcontrollers programmed with Fuzzy Logic ontroller (FLC) and a ystem Handler are employed to control and monitor the fingers and the thumb to replicate the desired hand action of the grasp, the key pinch, the pulp to pulp pinch, the tripod pinch, and the open hand. Each finger is equipp d with position sensors at the pi ot joints and a tactile-pressure sensor at the fingertip. The finger mo ements are programmed to follow given set points and stopped ,. h ne er an obstacle is encountered and the pressure of the tactile sensor exceeds a specified limit. This allows the fingers and thumb to wrap round an object without crushing it. DC motors with reduced gear heads are used as actuators and they are dri en by H-Bridge sv itches. Input signals to the switches in the form of Pulse Width Modulation (PWM) and direction signals are generated by the microcontroller . The signal r present control action of the FLC. Membership functions of the FLC were tuned and the rule \ ere formed to obtain the desired response. Distributed control is implemented by conn cting all finger microcontrollers to a main microcontroller that can b integrated with the Brain omputer Interface. The o erall system was constructed and te ted successfully to control the prosthetic hand