Roelof D. Schuiling

Synthesis and paragenesis of Na-beidellite as a function of temperature, water pressure, and sodium activity

In the chemical system Na2O-Al2O3-SiO2-H2O, the stability field of Na-beidellite is presented as a function of pressure, temperature, and Na- and Si-activity. Na0.7-beidellite was hydrothermally synthesized using a stoichiometric gel composition in the temperature range from 275° to 475°C and at pressures from 0.2 to 5 kbar. Below 275°C kaolinite was the only crystalline phase, and above about 500°C paragonite and quartz developed instead of beidellite. An optimum yield of 95% of the Na0.7- beidellite was obtained at 400°C and 1 kbar after 20 days. Gels with a Na-content equivalent to a layer charge lower than 0.3 per O20(OH)4 did not produce beidellite. They yielded kaolinite below 325°C and pyrophyllite above 325°C. With gels of a Na-content equivalent to a layer charge of 1.5, the Na-beidellite field shifted to a minimum between temperatures of 275° and 200°C. This procedure offers the potential to synthesize beidellite at low temperatures. Beidellite synthesized from Na1.0-gel approach a Na1.35 composition and those from Na1.5- and Na2.0-gels a Na1.8 composition.

The interlayer collapse during dehydration of synthetic Na (sub 0.7) -beidellite; a 23 Na solid-state magic-angle spinning NMR study

The dehydration and migration of the interlayer cation of the synthetic beidellite Na0.7Al4.7Si7.3O20-(OH)4·nH2O, were studied with solid-state 23Na and 27Al MAS-NMR, heating stage XRD, and thermogravimetric analyses (TGA, DTA). The 23Na MAS-NMR of Na-beidellite at 25°C displays a chemical shift of 0.2 ppm, which indicates a configuration comparable with that of Na+ in solution. Total dehydration proceeds reversibly in two temperature ranges. Four water molecules per Na+ are gradually removed from 25° to 85°C. As a result, the basal spacing decreases from 12.54 Å to 9.98 Å and the Na+ surrounded by the two remaining water molecules is relocated in the hexagonal cavities of the tetrahedral sheet. The chemical shift of 1.5 ppm exhibited after the first dehydration stage illustrates the increased influence of the tetrahedral sheet. The high local symmetry is maintained throughout the entire first dehydration stage. During the second dehydration, which proceeds in a narrow temperature range around 400°C, the remaining two water molecules are removed reversibly without any change of the basal spacing.

Enhanced silicate weathering is not limited by silicic acid saturation.

Enhanced weathering of olivine as a means of sequestering carbon is investigated by Kohler et al. (1). Specifically, the study discusses the potential distribution of fine olivine powder, obtained from dunite mines, in the humid tropic regions of the Amazon and Congo River catchments. Olivine (forsterite) dissolution (Eq. 1) implies the sequestration of 4 moles of CO2 for each mole of olivine (2).

Power from closing the Red Sea: economic and ecological costs and benefits following the isolation of the Red Sea

The closure of the Red Sea at its southern entrance (the Bab-al-Mandab Strait) could well lead to the worlds largest hydropower generation, in the order of 50 000 MW. The cost and time-scales involved are beyond normal economical considerations. Macro-engineering projects of this size cause a massive destruction of existing ecologies. On the positive side of the environmental scale, however, are the big reductions of greenhouse gas emissions, and the reduced pace of fossil hydrocarbon resource exhaustion. This paper examines the ethical and environmental dilemmas and some of the political implications of macro-engineering, as exemplified by the Bab-al-Mandab project. The precautionary principle does not offer a guideline in such a decision, as it not only seeks to avoid irreparable ecological changes but also concerns the well-being of future generations of people living around the Red Sea, which is promoted by access to a large and emission-free source of energy.

Mineral Sequestration of CO2 and Recovery of the Heat of Reaction

Apart from saving energy, sequestration of CO2 is the most direct way of combating the excessive greenhouse effect. Current approaches focus mainly on CO2 storage in gaseous form in abandoned gas fields or aquifers. Sequestration in mineral form is still in its infancy, because the dry carbonation of common Mg- or Ca-silicates is unsuccessful. It can be deduced from natural examples that wet sequestration, combining hydration and carbonation is likely to be more successful. Several approaches are explored in this paper, either in situ in dunite massifs (olivine-rich rocks), or by reacting crushed olivine off-site in contained spaces with the off gases of thermal plants. The reaction produces a large amount of heat, which can be recovered as high enthalpy steam. In order to be effective, however, it should only be applied to large volumes of olivine, in a typical macro-engineering fashion, as the heat losses become unacceptably high in small systems with a high surface to volume ratio. One possibility would be to fill half of abandoned deep opencast mines with ground olivine and cover it by backfill. In the bottom part a mixture of hot CO2 and steam is injected in order to set up a convective system similar to geothermal systems

The Hormuz Strait Dam Macroproject— 21st Century Electricity Development Infrastructure Node (EDIN)?

ABSTRACT Ocean gulfs offer a means of artificially creating a depression, which can be used for a regionally significant hydroelectric macroproject. We examine here the case for a dam at the Strait of Hormuz that blocks a large gulf situated in an arid region. A 35 m evaporation of this concentration basin will reduce its watery surface area by ∼53% and allow generation of ∼2.050 MW (or possibly ∼2.500 MW) of electricity. Our conclusion is that the proposed Electricity Development Infrastructure Node (EDIN) is a feasible and desirable macroproject. If the macroproject starts in the near-term future, it would require a significant change in the logistics of oil and gas transport from this region. Alternatively, it can be considered as an attractive future solution for the energy requirements of the region after exhaustion of its oil and gas reserves.

Olivine Hills: Mineral Water Against Climate Change

Rainwaters passing through olivine-bearing rocks are transformed into magnesium-bicarbonate mineral waters, thereby capturing CO2 in a safe and sustainable way. It is estimated that this weathering of mafic and ultramafic rocks (silicate rocks rich in magnesium and calcium) accounts for an annual sequestration in the order of 2–2.5 billion tons of CO2. In preindustrial times this was enough to balance the input of CO2 from the Earth’s mantle. On a truly megaengineering scale we propose to restore the balance by enhancing the rate of weathering of such rocks worldwide. As a small, but very visible part of this approach every town in the world that is genuinely concerned about climate change should erect a large hill of olivine powder in an attractive location in or around the town. Rain, or a nice fountain on the hilltop should provide water that will pass first through the topsoil and then through the olivine powder. When the water reacts with the olivine it will sequester CO2. If any CO2 -rich stack gases are available nearby, these can be injected near the bottom of the olivine pile in order to make the capture of CO2 even more effective. As a bonus it can be mentioned that magnesium bicarbonate waters are very healthy, notably effective against cardiovascular diseases and diabetes. Olivine hills could also be constructed as a refuge in times of flooding, thus combining adaptation and mitigation on a modest scale.

Six commercially viable ways to remove CO2 from the atmosphere and/or reduce CO2 emissions

BackgroundThe burning of fossil fuels is the main cause of rising CO2 levels of the atmosphere. This will probably result in climate change. Another consequence is ocean acidification. Although these consequences are not yet proven beyond doubt, the risk of doing nothing is too large. The simplest response is the removal and sustainable storage of CO2. By reaction with basic minerals, nature has sequestered almost all of the CO2 that has ever been released by the planet. This weathering continues to play a role but nature cannot cope with the ongoing much (30 to 60 times) higher rates of anthropogenic greenhouse gas emissions.ResultsIn this paper six approaches are described which take advantage of the natural process of weathering and solve other problems as well, thereby making them cost-effective. All six make the maximum use of natural conditions (climate, tides, currents), natural materials (olivine, serpentine), and organisms (diatoms, hyperaccumulator plants).ConclusionsImpacts on the environment are minimized or even turned into benefits.

Capturing CO2 from air

Schellnhuber (1) proposed some well-known solutions to the climate problem: i) Phasing out of CO2 in the next decades ii) Energy efficiency iii) Emission reduction iv) Systematic decarbonation v) Efficiency and renewables These suggestions are commendable, but their suggested time scheme lacks realism. The emerging economies (China, India, and Brazil) want to develop their economies and raise the standard of living. A prerequisite is access to abundant and cheap energy. They want to realize their objectives by using their large coal reserves. The climate problem can be solved by removing CO2 from the atmosphere. House et al. (2) state that capturing CO2 from the air costs around

Asteroid impact in the black sea; a black scenario

1,000 per tonne. They have obviously not looked at enhanced weathering of olivine. We have shown that enhanced weathering of olivine leads to mineral carbonation at