Benny K.G. Theng

Bio: Benny K.G. Theng is an academic researcher from Landcare Research. The author has contributed to research in topics: Allophane & Halloysite. The author has an hindex of 28, co-authored 70 publications receiving 4688 citations.

Handbook of clay science

Abstract: 1. General Introduction: Clays, Clay Minerals, and Clay Science 2. Structures and Mineralogy of Clay Minerals 3. Surface and Interface Chemistry of Clay Minerals 4. Synthetic Clay Minerals and Purification of Natural Clays 5. Colloid Clay Science 6. Mechanical Properties of Clays and Clay Minerals 7. Modified Clays and Clay Minerals 8. Properties and Behavior of Iron in Clay Minerals 9. Clays, Microorganisms and Biomineralisation 10. Clays in Industry 11. Clays, Environment and Health 12. Critical Assessment of Some Analytical Techniques 13. Some Other Materials Related to Clays 14. Genesis of Clay Minerals 15. History of Clay Science: A Young Discipline 16. Teaching Clay Science: A Great Perspective

Intercalation Method Using Formamide for Differentiating Halloysite from Kaolinite

Abstract: A rapid and simple test to distinguish halloysite from kaolinite in mineral mixtures has been developed based on differences in the rate and extent of formamide intercalation. With halloysite, complex formation was both rapid (< 1 hr) and complete, whereas no significant intercalation occurred with kaolinite until at least 4 hr after contact with formamide, and then the process may not have been complete. Unheated halloysite formed complete complexes with formamide regardless of the interlayer hydration state of the mineral. The test, however, was inconclusive for halloysite that had been oven- dried at 110~C, although some water may still have been present in the interlayer space. The extent of formamide intercalation by kaolinite was likely influenced by sample crystallinity, and the rate of complex formation was enhanced by the addition of up to 10% v/v water to the system. Nevertheless, the formamide test unambiguously differentiated halloysite from kaolinite. N-methylformamide, which yields complexes with a basal spacing of 10.9/k, could be substituted for formamide (basal spacing = 10.4 A) for samples containing appreciable amounts of illite-mica.

Nanoparticles in the Soil Environment

Abstract: Soils contain many kinds of inorganic and organic particles with at least one dimension in the nanoscale or colloidal range (<100 nm). Well-known examples are clay minerals, metal (hydr)oxides, and humic substances, while allophane and imogolite are abundant in volcanic soils. Apparently, only a small proportion of nanoparticles in soil occur as discrete entities. Organic colloids in soil, for example, are largely associated with their inorganic counterparts or form coatings over mineral surfaces. For this reason, individual nanoparticles are difficult to separate and collect from the bulk soil, and extraction yields are generally low. By the same token, the characterization of soil nanoparticles often requires advanced analytical and spectroscopic techniques. Because of their large surface area and the presence of surface defects and dislocations, nanoparticles in soil are very reactive towards external solute molecules. The focus of research in recent years has been on the interactions of nanoparticles with environmental pollutants and on their impact on the movement, fate, and bioavailability of contaminants.

Metals, minerals and microbes: geomicrobiology and bioremediation

Abstract: Microbes play key geoactive roles in the biosphere, particularly in the areas of element biotransformations and biogeochemical cycling, metal and mineral transformations, decomposition, bioweathering, and soil and sediment formation. All kinds of microbes, including prokaryotes and eukaryotes and their symbiotic associations with each other and 'higher organisms', can contribute actively to geological phenomena, and central to many such geomicrobial processes are transformations of metals and minerals. Microbes have a variety of properties that can effect changes in metal speciation, toxicity and mobility, as well as mineral formation or mineral dissolution or deterioration. Such mechanisms are important components of natural biogeochemical cycles for metals as well as associated elements in biomass, soil, rocks and minerals, e.g. sulfur and phosphorus, and metalloids, actinides and metal radionuclides. Apart from being important in natural biosphere processes, metal and mineral transformations can have beneficial or detrimental consequences in a human context. Bioremediation is the application of biological systems to the clean-up of organic and inorganic pollution, with bacteria and fungi being the most important organisms for reclamation, immobilization or detoxification of metallic and radionuclide pollutants. Some biominerals or metallic elements deposited by microbes have catalytic and other properties in nanoparticle, crystalline or colloidal forms, and these are relevant to the development of novel biomaterials for technological and antimicrobial purposes. On the negative side, metal and mineral transformations by microbes may result in spoilage and destruction of natural and synthetic materials, rock and mineral-based building materials (e.g. concrete), acid mine drainage and associated metal pollution, biocorrosion of metals, alloys and related substances, and adverse effects on radionuclide speciation, mobility and containment, all with immense social and economic consequences. The ubiquity and importance of microbes in biosphere processes make geomicrobiology one of the most important concepts within microbiology, and one requiring an interdisciplinary approach to define environmental and applied significance and underpin exploitation in biotechnology.

Grassland management and conversion into grassland: effects on soil carbon

Abstract: Grasslands are heavily relied upon for food and forage production. A key component for sustaining production in grassland ecosystems is the maintenance of soil organic matter (SOM), which can be strongly influenced by management. Many management techniques intended to increase forage production may potentially increase SOM, thus sequestering atmospheric carbon (C). Further, conversion from either cultivation or native vegetation into grassland could also sequester atmospheric carbon. We reviewed studies examining the influence of improved grassland management practices and conversion into grasslands on soil C worldwide to assess the potential for C sequestration. Results from 115 studies containing over 300 data points were analyzed. Management improvements included fertilization (39%), improved grazing management (24%), conversion from cul- tivation (15%) and native vegetation (15%), sowing of legumes (4%) and grasses (2%), earthworm introduction (1%), and irrigation (1%). Soil C content and concentration in- creased with improved management in 74% of the studies, and mean soil C increased with all types of improvement. Carbon sequestration rates were highest during the first 40 yr after treatments began and tended to be greatest in the top 10 cm of soil. Impacts were greater in woodland and grassland biomes than in forest, desert, rain forest, or shrubland biomes. Conversion from cultivation, the introduction of earthworms, and irrigation resulted in the largest increases. Rates of C sequestration by type of improvement ranged from 0.1 1 to 3.04 Mg C-ha-l yr-l, with a mean of 0.54 Mg C-ha-l yr-l, and were highly influenced by biome type and climate. We conclude that grasslands can act as a significant carbon sink with the implementation of improved management.