Microwave-Assisted Extraction of Rare Earth Elements from Petroleum Refining Catalysts and Ambient Fine Aerosols Prior to Inductively Coupled Plasma - Mass Spectrometry

In the absence of a certified reference material, a robust microwave-assisted acid digestion procedure followed by inductively coupled plasma - mass spectrometry (ICP-MS) was developed to quantify rare earth elements (REEs) in fluidized-bed catalytic cracking (FCC) catalysts and atmospheric fine particulate matter (PM2.5). High temperature (200 C), high pressure (200 psig), acid digestion (HNO3, HF, and H3BO3) with 20 minute dwell time effectively solubilized REEs from six fresh catalysts, a spent catalyst, and PM2.5. This method was also employed to measure 27 non-REEs including Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb, and U. Complete extraction of several REEs (Y, La, Ce, Pr, Nd, Tb, Dy, and Er) required HF indicating that they were closely associated with the aluminosilicate structure of the zeolite FCC catalysts. Internal standardization using 115In quantitatively corrected non-spectral interferences in the catalyst digestate matrix. Inter-laboratory comparison using ICP-optical emission spectroscopy (ICP-OES) and instrumental neutron activation analysis (INAA) demonstrated the applicability of the newly developed analytical method for accurate analysis of REEs in FCC catalysts. The method developed for FCC catalysts was also successfully implemented to measure trace to ultra-trace concentrations of La, Ce, Pr, Nd, Sm, Gd, Eu, and Dy in ambient PM2.5 in an industrial area of Houston, TX

Quality and Membrane Treatability of the Lake Houston Water Supply

Currently, sections of Harris and Montgomery counties located North and Northeast of Houston use groundwater almost exclusively. These areas have witnessed substantial population growth and associated increases in water demand. In 1999 approximately 60% of potable water in Houston and its adjoining communities was produced from surface water. The remaining approximately 40% was derived from groundwater. However, the "Subsidence District" which is the authority responsible for granting groundwater permits has mandated that groundwater use needs to be decreased to 20% within the next few years so as to limit subsidence. Pipelines are not available to distribute purified water from the existing surface water treatment plants located in the South and East of Houston to the Northern areas that actually require additional water. Because Lake Houston is located in the geographical area of interest and is a surface water source, the City of Houston is interested in developing it for its future water needs. Additionally, a favorable hydraulic gradient exists from the Lake to the proposed service areas in Harris and Montgomery counties. Federal regulations such as the Stage II of the Disinfectant/Disinfection By-Products Rule (1) and the Enhanced Surface Water Treatment Rule (2) are expected to be promulgated in the near future. These rules are anticipated to introduce more stringent maximum contaminant levels (MCLs) for total trihalomethanes (THMs) and haloacetic acids (HAAs), possibly introduce new MCLs for individual species of THMs and HAAs, reduce turbidity levels, and enhance inactivation/removal requirements for Cryptosporidium. (Cryptosporidium was the causative protozoan for the more than 400,000 cases of acute gastrointestinal disease in Milwaukee, WI in March 1993.) The treatment processes in the City of Houston's existing water purification plants are not expected to be sufficient in meeting these anticipated regulations. Therefore, both regulatory requirements and engineering considerations point towards Lake Houston as an attractive surface water source for the next water purification plant to supply potable water to the City and its adjoining communities. However, water quality in Lake Houston can be characterized as being poor with high concentrations of turbidity, color, total organic carbon (TOC), nutrients such as phosphorus and nitrogen, etc. (3). Pressure-driven membrane processes can be employed as effective barriers against a wide range of contaminants including particles, turbidity, protozoan cysts and oocysts, bacteria, viruses, color, organic carbon, disinfection by-product (DBP) precursors, and dissolved metals. Additionally, microfiltration (MF) and ultrafiltration (UF) pretreatment may be necessary to reduce fouling rates and increase chemical cleaning intervals during surface water nanofiltration (NF) (4). Therefore, an integrated membrane system employing MF or UF pretreatment to NF is expected to be an important treatment candidate for Lake Houston water. Nanofiltration (NF) membranes typically operate at pressures less than 100 psi and are capable of high rejections of natural organic matter (NOM) and precursors to disinfection by-products (DBP) including trihalomethanes (THMs) and haloacetic acids (HAAs) (5-8), many of which are suspected carcinogens, mutagens, or teratogens

Predicting Ro/Nf Water Quality By Modified Solution Diffusion Model And Artificial Neural Networks

Membrane solute mass transfer is affected by physical-chemical properties of membrane films, solvent (water) and solutes. Existing mechanistic or empirical models that predict finished water quality from a diffusion controlled membrane can be significantly improved. Modelling membrane solute mass transfer by diffusion solution model is generally restricted to developing specific solute mass transfer coefficients that are site and stage specific. A modified solution diffusion model and two artificial neural network models have been developed for modelling diffusion controlled membrane mass transfer using stage specific solute MTCs. These models compensate for the effects of system flux, recovery and feed water quality on solute MTC and predict more accurately than existing models. © 2005 Elsevier B.V. All rights reserved

Natural atmospheric deposition of molybdenum: a global model and implications for tropical forests

Abstract Molybdenum (Mo) is an essential trace metal that plays a central role in biological nitrogen fixation (BNF) as the cofactor in the conventional form of the nitrogenase enzyme. The low availability of Mo in soils often constrains BNF in many terrestrial ecosystems. Atmospheric sources may supply a critical source of exogenous Mo to regions with highly weathered soils likely low in Mo, particularly in tropical forests where BNF is thought to be high. Here, we present results of a global model of Mo deposition that considers the principal natural sources of atmospheric Mo—windborne mineral dust, sea-salt aerosols, and volcanic sources—which operate over geologic time. The largest source of mineral dust globally is from North Africa. We quantified Mo concentrations in dust and sediments from the Bodélé Depression, a large source within North Africa, to constrain our model. Because the Mo concentration of seawater is relatively high for a trace element, we also hypothesized that sea-salt aerosols would contribute atmospheric Mo. Our model predicts higher Mo deposition to terrestrial ecosystems along coasts downstream in trade winds, near active volcanoes, and in areas that receive dust deposition from North Africa, such as the northern Amazon Basin, the Caribbean, and Central America. Regions with higher Mo deposition tend to be areas where BNF has previously been measured. The lowest Mo deposition occurs in the high latitudes, northern parts of North America, Western Australia, Southern Africa, and much of central South America. Atmospheric transport of Mo likely plays an important role in supplying Mo to ecosystems across geologic time, particularly in regions with highly weathered soils

Restoring India's Terrestrial Ecosystems: Needs, Challenges, and Policy Recommendations

<p>This document is a product of the preparatory phase project of the National Mission on Biodiversity and Human Well-Being which was catalysed and supported by the Office of the Principal Scientific Advisor to the Government of India. It is the outcome of a series of stakeholder consultation meetings on ecological restoration of terrestrial landscapes and climate change in India. The insights from these meetings have been used to develop this document which highlights the challenges and best-practices in the restoration of terrestrial ecosystems, can serve as a guide for successful restoration of landscapes across different biomes of the Indian subcontinent, and help achieve India’s commitments to the Bonn Challenge and the goals set by India for biodiversity conservation, land restoration, climate mitigation and adaptation.</p&gt

Data from: Anthropogenic Perturbations to the Atmospheric Molybdenum Cycle

Molybdenum (Mo) is an essential trace element that is, important for terrestrial and aquatic ecosystems, as it is required for biological nitrogen fixation and uptake. Mo is carried in particles to the atmosphere from sources such as desert dust, sea spray, and volcanoes resulting in losses and sources to different ecosystems. Atmospheric Mo deposition is essential on long time scales for soils which have lost Mo due to soil weathering, with consequences for nitrogen cycling. Anthropogenic changes to the Mo cycle from combustion, motor vehicles, and agricultural dust, are likely to be large, and have more than doubled sources of Mo to the atmosphere. Locally, anthropogenic changes to Mo in industrialized regions can represent a 100‐fold increase in deposition, and may affect nitrogen cycling in nitrogen‐limited ecosystems. This dataset supports these findings.We acknowledge the Atkinson Center for funding for this project, and NSF CCF-1522054