Mass transfer in bubble column contractors

Gas holdup and overall volumetric mass transfer coefficients in bubble column contactors have been investigated for water and aqueous electrolyte solutions. Two methods were used to obtain experimental data on volumetric mass transfer coefficients: the steady state oxidation technique and a transient method. The former technique was found to be unsuitable for absorption measurements because chemical enhancement of mass transfer, due to simultaneous absorption and fast reaction, caused erroneously high mass transfer coefficients to be evaluated. In the transient experiments the effect of superficial gas velocity, concentration of electrolytes in solution, bubble column diameter and gas inlet orifice diameter on the gas holdup and the mass transfer rate, were investigated. The experimental data for gas holdup and overall mass transfer coefficients obtained both in this study and from the literature have been correlated by dimensionless equations

In situ synthesis of zeolitic imidazolate frameworks/carbon nanotube composites with enhanced CO2 adsorption

A series of ZIF-8 and hydroxyl-functionalized carbon nanotube (CNT) composites were successfully synthesized by the solvothermal method. The obtained ZIF-8/CNT composites were characterized by XRD, SEM, TGA and N2 adsorption at 77 K. The contents of ZIF-8 and CNTs in the composites were calculated from thermal analysis data. CO2 and N2 adsorption at 273 K on the composites was also investigated and compared. The ZIF-8 particles in the composites exhibit similar crystal structures and morphology to those of pure ZIF-8, but display enhanced thermal stability. The surface areas and pore volumes of the ZIF-8/CNT composites are higher than the values calculated for hypothetical physical mixtures, and the synergetic effect between ZIF-8 and CNTs can be proposed. This phenomenon demonstrates that the incorporation of CNTs into ZIF-8 can facilitate the nucleation and crystallization of ZIF-8. As a result, the composites with an optimal CNT content (3.63 wt%) show improved CO2 adsorption capacity and higher relative selectivity for CO2/N2 compared with pure ZIF-8

Survey of persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of rural, urban and industrial areas of Concepción, Chile, using passive air samplers

Passive air samplers (PAS) consisting of polyurethane foam (PUF) disks were used to assess air concentrations of polychlorinated biphenyl (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) in rural, urban, and industrial sites in Concepcion, Chile during a two-month deployment in the summer of 2007. Results for PCBs and PAHs showed a clear rural-urban-industrial gradient. PCB air concentrations (pg m(-3)) ranged from similar to 30 to similar to 350 and were similar to 2 to 5 times higher at industrial sites compared to rural sites. For PAHs, air concentrations (ng m(-3)) ranged from 26 to 230 and were 4 to 8 times higher at industrial sites. The PCB congener profile was dominated by high molecular weight PCBs at urban and industrial sites. The PAH profile was dominated by 3- and 4-ring PAHs accounting for more than 90% of the Sigma(15)PAH, and dominated by phenanthrene (similar to 40%). Of the HCH isomers, only gamma-HCH was detected with air concentrations ranging from 5 to 120 pg m(-3). While for DDT isomers, p,p'-DDE was the only compound detected, ranging from below detection limit (BDL) to 360 pg m(-3). Other OCPs (chlordanes, heptachlor and Dieldrin) showed low air concentrations (pg m(-3)) on the order of similar to 1 - 3. Endosulfan, which is a newly listed persistent organic pollutant (POP) under the Stockholm Convention (SC) on POPs, ranged from 14 to 20 pg m(-3). Polybrominated diphenyl ethers (PBDEs) also newly listed under the SC, were relatively uniform across the transect with air concentrations (pg m(-3)) in the range of similar to 5 to 10. This study represents one of the first efforts to characterize the POPs composition in ambient air for urban and industrial areas of Chile

Planning for nuclear security: Design Basis Threats and physical protection systems

A Design Basis Threat was developed which was based on the threat the facility was exposed to in terms of its assets including the radioactive source. The purpose of this was to serve as a tool providing a common basis for planning for physical protection system by the operator and approval of its physical protection plan by the competent authority for nuclear security. The DBT assessment methodology is an IAEA recommended method which is best to design the security measures for specific radioactive sources. This method has a correlation between risk and security systems. The higher the risk, the more capability will be required from the security systems to protect the sources.

Preparation and characterisation of manganese and iron compounds as potential control-release foliar fertilisers

Nanoscale crystals containing manganese and iron as potential foliar fertilizers have been further investigated with the experience accumulated from previous research on potential zinc foliar fertilizer. Compared to Zn(II), Mn(II) and Fe(II) are easily oxidisable in ambient environment, adding stricter criteria to compound selection to prevent oxidation. Adoption of phosphate buffer saline system and chelate have been proposed as the solution and extensively assessed in this paper. After quick co-precipitation, as-prepared crystals were characterised via XRD, FTIR, SEM, TEM, elemental analysis, and AAS to confirm the compositions and two-dimensional nanoscale morphology and assess the nutrient ion release and aqueous stability. In particular, the available Mn concentration in manganese ammonium phosphate and manganese oxalate suspensions was similar to 10 and similar to 110 mg/L, respectively. In comparison, ferrous ammonium phosphate and ferrous oxalate suspensions contained similar to 10 and similar to 30 mg/L of iron ions, respectively. Therefore, these suspensions can all be used as long-term foliar fertilizers for the correction of Mn and Fe deficiency in plants

Hierarchically structured metal–organic framework/vertically-aligned carbon nanotubes hybrids for CO 2 capture

A novel carbon/metal–organic framework composite was synthesized by confined growth of HKUST-1 in the interspace of the vertically-aligned carbon nanotube (VACNT) arrays. The grown HKUST-1 crystals are much smaller than the HKUST-1 crystals produced without the confinement growth. The derived HKUST-1/VACNT hybrids possess a hierarchical microporous–mesoporous structure. In comparison to the calculated hypothetical value assuming the physical mixture of the components, the synthesized HKUST-1/VACNT composites exhibit larger surface area and porosity, higher CO2 adsorption amount, and better CO2/N2 selectivity, which indicate the positive synergistic effect between HKUST-1 and VACNT. Besides the superior adsorption properties of hybrids, they are easier to handle than powder adsorbent for gas storage/separation

Biogenic methane production from Bowen Basin coal waste materials

A microbial consortium derived from sewage sludge from the treatment of wastewater (Luggage Point Wastewater Treatment Plant, Brisbane, Australia) has been applied to Jameson Cell (J-cell) rejects (R\ua0=\ua00.96\ua0±\ua00.008) of a Bowen Basin coal preparation plant to assess the potential for biogenic methane production. A maximum methane yield of 26.20\ua0μmol/g J-cell rejects (0.64\ua0m\ua0CH/ton) was observed, suggesting biogenic methane production from coal waste materials is a feasible process if yields can be improved. Molecular analysis performed on the microbial consortium showed similar microbial community compositions to those observed in natural coal bed environments. The study demonstrates that Australian coal waste materials can be used as a viable feedstock for biogenic methane production using microorganisms that are not native within the coal beds

Aquaponics

poster abstractThis document outlines the low level design for an aquaponics system. This system is intended to be fully automated and modular, running without the necessity direct end-user input or technical knowledge. The system was designed by the 2014 MURI Grant Aquaponics Team, directed by Dr. David Goodman, and Mr. Bob Durkin. This aquaponics system consists of an aquaculture tank, used to grow freshwater prawns, a reservoir tank, a de-chlorination tank; three horticultural grow beds used to cultivate greens, and an automation system for water flow, temperature, dissolved oxygen, and PH control. These components are combined together in a modular stand designed for use in a ten foot by ten foot area. The design of this system was broken up into tasks assigned to individual members of Dr. Goodman’s aquaponics team. Each team member was responsible for the research and design of all aspects of his individual task. The end goal of this project is to create a marketable, ‘green living’ indoor garden for use in residential homes and apartments. This aquaponics system will be modular in order to fulfill the needs of the consumer, and automated in order to be used without technical skill or knowledge of the end user