Robert F. Benson

A micro-fluidic galvanic cell as an on-chip power source

We present a micro-fluidics actuated galvanic cell for on demand power generation. The galvanic cell is an aluminum anode/alkaline electrolyte/air cathode cell. The concept is based upon an actuation mechanism that pushes an electrolyte into a micro-channel containing electrodes. When the electrolyte reaches the electrodes of a galvanic cell, it produces energy through an electrochemical reaction. The proof of concept is presented herein by fabricating and characterizing a single cell using micro-fabrication techniques. The actuation mechanism is based on the thermal expansion of a working fluid. A brief discussion on the optimization of this actuation is also presented. The open voltage of this micro-cell was experimentally measured to be around 1.9 V. The Al/air galvanic cell chemistry has been compared with commercial Zn/air battery and has been found to perform better. The present micro-cell design (with an area of 0.75 cm 2 ), is capable of providing an energy of 5 J after 6.0 min when subjected to a load of 20 � . The actuation mechanism takes less than a minute and consumes about 3.5 J.

Extraction of Heavy Metals by Amines Adsorbed onto Silica Gel

Abstract Previous work has established the possibility of using known coordinating agents supported on silica gel in the removal of heavy metals such as lead, copper, cadmium, and nickel from aqueous media. Functionalized silica gel has been used in the removal of heavy metals with notable success. Silica gel is currently being used as a support for various monofunctional aliphatic amines as coordinating ligands. The current study reports the results of an investigation involving the use of saturated, straight chain primary amines as coordinating ligands in the removal of copper(II), cadmium(II), lead(II), nickel(II), and silver(I) ions from aqueous solutions of known concentration. Primary amines used in this investigation were n-butylamine, n-hexylamine, n-octylamine, n-decylamine, and n-hexadecylamine.

EXTRACTION OF HEAVY METALS BY MERCAPTANS ATTACHED TO SILICA GEL BY A CORKSCREW MECHANISM

ABSTRACT Saturated, straight chain mercaptans were attached to silica gel and used as coordinating agents for removal of cadmium(II), copper(II), lead(II), and nickel(II) ions from standard solutions. It is believed that the mercaptans become wedged in the silica pores, but are available for reaction. Four thiols were used, viz., 1-hexanethiol, 1-dodecanethiol, 1-hexadecanethiol, and 1-octadecanethiol. Standard solutions of metals (1.57 mM) were stirred with the supported mercaptans for two hours, and at 25°C, and the sample supernatants were analyzed using atomic absorption spectrometry. At pH = 8, the percent removal was 99 (Cd), 91.5 (Cu), 80.8 (Pb), and 97 (Ni). It was possible to acidify the metal-containing solids, and regenerate the supported chelating agents.

ACCUMULATION AND RETENTION OF LEAD BY CATTAIL (TYPHA DOMINGENSIS), HYDRILLA (HYDRILLA VERTICILLATA), AND DUCKWEED (LEMNA OBSCURA)

ABSTRACT Investigation of lead levels in Delaney Creek, which flows through a former lead-acid battery manufacturing and disposal site in Tampa, FL, revealed low but significant lead levels in the water and sediments along the creek,[1] Known phytoaccumulator plants populate certain locations within the creek and adjacent wetlands. Three representative plants from the study site—cattail (Typha domingensis Pers.), hydrilla (Hydrilla verticillata Royle), and duckweed (Lemna obscura L.)—were investigated for their potential to remove lead from contaminated waters under the controlled conditions of a phytotron room. The plants were collected at the site and cultured in hydroponic medium under conditions that mimicked their natural environment (26°C and 80% humidity). Results indicate that, of the three species, duckweed and hydrilla achieve high lead removal efficiencies after a short exposure period (98% removal using hydrilla, 97% with duckweed after one week of exposure) while cattail appears to be less efficient than the other two species. The kinetic rates of lead removal were studied for Lemna obscura.

Supported chelating agents in remediation. The corkscrew model

Abstract High‐porosity, high‐surface area, inert, solid substrates have been used for many years to support reactive phases. Solid substrates supporting liquid phases have been the basis of gas and liquid chro‐matographic techniques. In the present study, supported chelating agents were successful in the treatment of aqueous solutions for ion extraction. In particular, a s‐diketone (LIX® 54), supported upon silica gel, was used in one step to extract copper ions from solution (749 ppm) to levels of approximately 1 ppm in a two‐minute contact time. This treatment shows an advantage over conventional liquid‐liquid extraction techniques. The 13‐diketone was incorporated on the solid substrate using a wedging or “corkscrew”; technique that promises to be useful.

Magnetic treatment of solid carbonates, sulfates, and phosphates of calcium

Abstract Anti‐scale magnetic treatment was applied to four calcium compounds that are known to be scale formers. Aqueous suspensions of the compounds were cycled through a closed‐system consisting of PVC pipe and a 1‐L reservoir in the absence (control) or presence (test) of a 2,000 gauss magnetic field. After a one‐hour treatment period, the suspensions were rapidly filtered, and aliquot portions of the filtrate were acidified and analyzed for calcium content by atomic absorptíon spectroscopy. Solubilities of test and control systems were compared, and the enhanced solubility (? s) of the test system over the control (s) was evaluated as a percentage increase over the control system solubility %change = 100 (? s)/s. The percent change was 25% (limestone), 14.7 % (calcite), 4.9% (gypsum) , 0.92% (dolomite), and 64% (tricalcium phosphate). In addition, the tendency to attain smaller average size distribution (comminution) was measured for all compounds. A hypothesis for the basis of anti‐scale magnetic treatment, and implications of the research are summarized.

Rapid Design, Fabrication and Optimization of a Single Event Thermo-Pneumatic Microactuation for the Delivery of Minute Amounts of Liquids

The need for efficient metering control of liquids in small devices has led to a boom in the advent of different micro-fluidic actuation mechanisms. Here we present a brief study on a thermal-pneumatic actuation mechanism for an on-demand delivery of minute amounts of liquids. A closely coupled, iterative design-fabrication strategy is used for optimization of a system in which no freely moving membranes are included. Special consideration was given to the heating device, minimizing the energy consumed. The fabrication method and performance of two types of fabricated resistors are compared herein. The first, a conventional Nickel-Chromium resistor using, lift-off micro-fabrication techniques, was initially tested. The second, a Copper cladded liquid crystal polymer in conjunction with a novel mask-less patterning system was used to produce nonconventional heating micro-ohmic heaters. The heating efficiency was proven to be superior using the latter approach. Various micro-fabricated fluidic devices have been designed as case studies and have been fabricated and integrated using a variety of materials to illustrate the functionality of the approach. The combination of design and fabrication steps, the simplicity of the resistive device, and the materials selected combined, yield a direct path to making fluidic transport devices for micro-analytical and power systems.Copyright

Fabrication of Micro-Actuated Galvanic Cells as Power on Demand for Lab on a Chip Applications by Means of Novel PCB/MEMS Technology

A novel copper-clad liquid crystal polymer material is proposed as a basic material for the construction of galvanic cells. Copper is an ideal material that allows not only the formation of conductor patterns in the material but also can be electroplated selectively with a wide variety of metals to create heterogeneous systems. The use of a novel mask-less patterning system described herein opens up the opportunity for micro fabrication of different microstructures that can be layered to form complex two and potentially three-dimensional micro fluidic networks. Achieving the photo-imprinting by the use of a novel mask-less system not only reduces the cost but also allows for ease and flexibility in making systems and is ideal for research and development environments. In this paper micro galvanic cells actuated by means of fluidic actuators have been designed and constructed. The electrochemical galvanic cells used as power source examples are a Daniell’s (Copper-Zinc) electrochemical battery, and an aluminum-air galvanic system. The choice for the electrochemical systems is discussed and some preliminary results are presented to show the levels of energy available. In addition, the basic concept of an electrically induced expansion mechanism for circuit activation on demand is described. Lastly, the mechanics of the suggested actuation mechanism are discussed.Copyright

Interaction of nitric oxide with the surface of stabilized calcium sulfate.

This work explores surface interactions between stabilized gypsum and nitric oxide. Gypsum is a common air-borne mineral particulate that has a potential two-fold relationship to the air pollution problem: as a particulate pollutant and as a catalyst or adsorbent for pollutant gases. Nitric Oxide is found in stack gases and automotive exhausts. Isotherms of nitric oxide adsorbed on stabilized gypsum were studied at 24 °C, 0°C, and −78°C. Coverages were related to a monolayer based upon a surface area of 17.0 m2/g as determined from a nitrogen adsorption isotherm and the B.E.T. method. Multilayer coverages containing both reversible and irreversible adsorption were observed for nitric oxide adsorbed on stablized hydrated calcium sulfate. An irreversible coverage of 41% at 24 °C and 61% at 0°C of the nitrogen monolayer was observed for nitric oxide adsorbed on hydration stabilized gypsum. The heat of adsorption at zero coverage was found to be 80.4 kJ/mol for nitric oxide on stabilized hydrated calcium sulfate for the irreversible adsorption and 7.5 kJ/mol for the reversible adsorption.

Iron Removal from Phosphoric Acid by Paramagnetism

Abstract A two-step separation technique was used in the laboratory to purify industrial grade phosphoric acid. Step 1 used a hydrocyclone, and step 2 used paramagetism. A total of 78.4% of the iron was removed without loss of phosphorus, mostly through step 1. In addition, 13% of the initial chromium was removed. Probably recycling or enhanced fields would enhance the removal of iron and chromium.