Synthesis of metal-organic frameworks (MOFs): routes to various MOF topologies, morphologies, and composites.

Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

Recent advances in the intercalation of metal complex cations in smectite clay minerals are leading to the development of new classes of selective heterogeneous catalysts. The selectivity of both metal-catalyzed and proton-catalyzed chemical conversions in clay intercalates can often be regulated by controlling surface chemical equilibria, interlamellar swelling, or reactant pair proximity in the interlayer regions. Also, the intercalation of polynuclear hydroxy metal cations and metal cluster cations in smectites affords new pillared clay catalysts with pore sizes that can be made larger than those of conventional zeolite catalysts.

https://science.sciencemag.org/content/sci/220/4595/365.full.pdf

Intercalated Clay Catalysts

A comprehensive review of the sequential extraction schemes for metal fractionation in environmental samples (i.e., sediment, soil, sewage sludge, fly ash, etc.) is presented. The review contains more than 400 references and covers principally the literature published over the last decade. The use of each reagent involved in these schemes is looked at critically, and guidelines for their selectivity and extraction capacity are given. The operational character of these schemes is emphasised. Topics such as comparability between sequential extraction schemes of widespread use, harmonisation, acceleration, validation, etc. are addressed and future developments outlined.

Chemical sequential extraction for metal partitioning in environmental solid samples.

Soil washing for metal removal: a review of physical/chemical technologies and field applications.

The ion-exchange selectivity of cesium and rubidium ions is studied in illite clay, saturated with either calcium, strontium, barium, sodium or potassium ions. The cesium- and rubidium-exchange levels studied vary between 50% and vanishingly low values. It is shown that the equilibria can be described in terms of three kinds of sites--corresponding to 0.5%, 3%, and 96.5% of the exchange capacity--each of which shows a characteristic selectivity coefficient. The site representing 0.5% of the capacity exhibits an exceedingly high selectivity for cesium ions (33 and 40 kJ/equiv with respect to sodium and calcium ions) and discriminates strongly between cesium and rubidium (6kJ/equiv). The equilibria on this site are thermodynamically reversible, as shown from three kinds of evidence: (1) the Cs-Rb trace selectivity difference, obtained from the equilibria in Ca, Sr, and Ba clay, agrees with the value obtained in the Na or K clay; (2) the same result is obtained from direct Cs-Rb trace mixture selectivity studies in Sr and Na clay; (3) the K-Na selectivity difference for this site as calculated from trace Cs equilibria agrees with the result obtained from Rb equilibria (11kJ/equiv). Finally, it is shown that the driving force for the high selectivity on this sitemore » is exclusively enthalpic.« less

Cesium and rubidium ion equilibriums in illite clay

Selenite reduction in Boom clay: Effect of FeS2, clay minerals and dissolved organic matter

Spectroscopic extended X-ray absorption fine structure (EXAFS) evidence was obtained on the chemical environment of 99Tc(IV) atoms formed upon introduction of TcO4- into four types of laboratory-scale synthetic and natural systems which mimic in situ natural reducing conditions in humic-rich geochemical environments:  (a) magnetite/pyrite in synthetic groundwater in the absence of humic substances (HSs), (b) magnetite/pyrite in natural Gorleben groundwater in the presence of HSs, (c) Boom clay sediment mixed with synthetic groundwater, and (d) Gorleben sand mixed with natural Gorleben groundwater. The investigated systems obey to pH 8−9 conditions, and all measured samples show similar EXAFS spectra for Tc, which could be fitted by a hydrated TcO2·xH2O phase. The results are interpreted as follows:  upon introduction of high concentrations (millimolar to micromolar) of TcO4- to chemically reducing environments, small Tc(IV) oxidic polymers are formed, which either may aggregate into larger units (colloids...

Evidence for the interaction of technetium colloids with humic substances by X-ray absorption spectroscopy.

The solid-phase Se speciation after short-term (3 weeks) contact of selenite [Se(IV)] oxyanions with pyrite (FeS2) and troilite (FeS) was investigated using X-ray absorption spectroscopy (XAS; X-ray absorption near-edge spectroscopy−extended X-ray absorption fine structure (XANES-EXAFS)). It was found that the nature of the sulfide mineral dictates the final speciation since respectively Se0 and FeSex were formed, meaning that the reaction mechanism is different and that these phases cannot be regarded as geochemically similar. The experimental results support the previously proposed sorption/reduction mechanism for the reaction of selenite with pyrite (8). In the presence of troilite the reduction proceeds through the intermediate formation of Se0 by reduction of selenite with dissolved sulfide. XAS data recorded for the FeS2 and FeS were compared with different Se reference phases, ranging in oxidation state from —II to +IV, used for validation of the XAS analysis methodology. This methodology can in pr...

André Maes

Papers

Cesium and rubidium ion equilibriums in illite clay

Selenite reduction in Boom clay: Effect of FeS2, clay minerals and dissolved organic matter

Evidence for the interaction of technetium colloids with humic substances by X-ray absorption spectroscopy.

XANES-EXAFS analysis of se solid-phase reaction products formed upon contacting Se(IV) with FeS2 and FeS.

Adsorption mechanism of humic and fulvic acid onto Mg/Al layered double hydroxides