Pore water chemistry applications

Electrokinetic remediation is limited by the type of contaminant, heterogeneities or anomalies in the soil, extreme pHs, pore water chemistry, lack of pore water, contaminant and noncontaminant ion concentrations, metals precipitation, and reduction-oxidation changes induced by the process electrode reactions. It may be difficult to estimate the time that will be required to remediate a site using this technology. Laboratory treatability testing may provide a false indication of the applicability of electrokinetic remediation at a specific site. Further research is required to determine the technology s limitations and ramifications. 

The application of lanthanides as indicators of paleoredox conditions must take into consideration their diagenetic chemistry (German and Elderfield 1990). More sensitive analytical methods are required before the lanthanide pore water chemistry of deep ocean sediments can be studied. This research subject is challenging and would provide answers to the transport rate of lanthanides across the sediment/water interface in pelagic enviromnents. 

Cochran JK (1984) The fates of U and Th decay series nuclides in the estuarine environment. In The Estuary as a Filter. Kennedy VS (ed) Academic Press, London, p 179-220 Cochran JK (1992) The oceanic chemistry of the uranium - and thorium - series nuclides. In Uranium-series Disequilibrium Applications to Earth, Marine and Environmental Sciences. Ivanovich M, Harmon RS (eds) Clarendon Press, Oxford, p 334-395 Cochran JK, Masque P (2003) Short-lived U/Th-series radionuclides in the ocean tracers for scavenging rates, export fluxes and particle dynamics. Rev Mineral Geochem 52 461-492 Cochran JK, Carey AE, Sholkovitz ER, Surprenant LD (1986) The geochemistry of uranium and thorium in coastal marine-sediments and sediment pore waters. Geochim Cosmochim Acta 50 663-680 Corbett DR, Chanton J, Burnett W, Dillon K, Rutkowski C. (1999) Patterns of groundwater discharge into Florida Bay. Linrnol Oceanogr 44 1045-1055... 

Kosian, P. A., Makynen, E. A., Monson, P. D. et al. (1998). Application of toxicity-based fractionation techniques and structure-activity relationship models for the identification of phototoxic polycyclic aromatic hydrocarbons in sediment pore water. Environmental Toxicology and Chemistry, 17, 1021-33. 

When water is present in the gas stream, it reacts with the SO, and O2 to produce sulfuric acid on the carbon surface, and can subsequently desorb. The overall SO adsorption capacity is enhanced due to its solubility in the water film that forms on the carbon surface. Conversely, active sites for SO2 capture are simultaneously reduced by water coverage. In general, the SO2 adsorption characteristics of an activated carbon are dependent upon its physical form, the pore structure, the surface area, and the surface chemistry. Similarly, both temperature and contact time also affect the efficiency of the process. The temperature for practical application is usually between ambient and 200°C, with ambient to 50°C being favored due to the decreasing solubility of SO2 in water at higher temperatures. 

Dr. Turov and Professor Leboda combine their expertise in nuclear magnetic resonance and adsorption phenomena to propose a new tool for a more incisive analysis of adsorbate-adsorbent interactions. Such an analysis is of critical importance in so many applications where it is becoming increasingly clear that adsorbate-carbon interactions are governed by both pore size and surface chemistry effects. These range from the ubiquitous water adsorption to the design of carbon-coated silicas with tailored ratios of hydrophobic to hydrophilic surface sites. 

To follow the environmental law and to remove small but sometimes persistent concentrations of pollutants activated carbons seem to be the media of choice. They are relatively inexpensive, easily to obtain, and owing to their enormously high surface area and pore volume, they are able to remove and retain even traces of air and water pollutants. Activated carbons, due to their unique surface chemistry act not only as adsorbents but also as catalysts for oxidation of inorganic and organic species. Moreover, their surface can be modified and tailored toward desired applications. 

Analyzing the effect of surface chemistry one should not forget about the effects of porosity. In fact the pores are significant assets of activated carbons used in environmental applications. As mentioned above, pores smaller than 5 mn should be especially active in the adsorption process due to the possibility to accommodate water together with MM molecules and thus due to formation of microreactors for DMDS synthesis. The dependence of the amount of DMDS formed on the carbon on their volume of pores less than 5 nm is plotted in Fig. 33. A good linear agreement with slope equal to 1.02 was found for samples for which the saturation conditions were reached... 

Activated carbon, in powdered (PAC) or granular (GAC) form, has many applications in drinking water treatment. It can be used for removing taste and odor (T O) compoimds, synthetic organic chemicals (SOCs), and dissolved natural ot] nic matter (DOM) from water. PAC typically has a diameter less than 0.15 mm, and can be applied at various locations in a treatment system (Fig. 1). GAC, with diameters ranging from 0.5 to 2.5 mm, is employed in fixed-bed adsorbers such as granular media filters or post filters. Despite difference in particle size, the adsorption properties of PAC and GAC are fundamentally the same because the characteristics of activated carbon (pore size distribution, internal surface area and smface chemistry) controlling the equilibrium aspects of adsorption are independent of particle size. However, particle size impacts adsorption kinetics. 

In contrast to the optimization of physical surface properties of activated carbons — where we know what is needed for a particular adsorption or water treatment task (an adequate surface area and a specific pore size distribution) and we also know how to achieve it very few guidelines were available for the optimization of the chemical surface properties. Much progress has been made in our understanding of the surface chemistry of carbons and in developing techniques for modifying it for catalyst support applications. So, in using carbons for water treatment we have long known how to modify their surface chemistry, but only recently have we learned what kind of surface chemistry we need for a specific... 

Research has shown that a solute with a diameter closer to that of zeolite pore dimension showed higher adsorption (close fit mechanism). An important consideration for applying zeolites in drinking water treatment practice is that their size exclusion and close fit adsorption mechanism makes them effective for the removal of specific solutes. [4]. Because the Si Al ratio allows for tuning of the surface properties and the resultant electrostatic double layer such membranes could also be tuned for specific ion-selective applications, but further work is needed to fully understand the connection between zeolite chemistry and membrane performance. Osewe (2014) investigated the dissipation half-life of malathion as affected by the largest window opening for FAU, MOR, and ZSM-5s zeolites [16]. 

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