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Processed spent bleaching earth (PSBE) is the end product derived from the processing of de-oiled spent bleaching earth (SBE) after the oil is recovered. Bleaching earth is very fine powder clay, and its main component is silicon dioxide used for refining process of palm oil and its by product is known as SBE is commonly disposed to landfill. The bleaching earth that is used for decolouring during the palm oils refining process form a solid sludge called the SBE. The SBE is generated in large quantities and it is becoming increasingly difficult to ignore the disposal of SBE when production of palm oil increases rapidly. Hence, the problem can be overcome by reusing solid waste as construction materials. In this study, the effect of using PSBE as a partial cement replacement in foamed concrete on durability resistance sulphate attack is investigated. Sulphate resistance in terms of expansion, loss in mass and loss in compressive strength after 52 weeks immersed in 5% sodium sulphate was evaluated. On the other hand, the microstructure changes in the specimens were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA). Comparisons are made between two mixtures which main ly control foamed concrete (FC) and foamed concrete containing 30% PSBE (PFC). Major findings show that when 30% PSBE added in a concrete mixture, after 52 weeks samples being immersed in 5% sodium sulphate, it will be more durable compared to control specimen (FC). It was recorded that change in mass, in expansion and loss in strength was 1.32%, 0.98% and 7.5% respectively. The microstructure study has confirmed that inclusion of PSBE in foamed concrete is known to improve the internal structure of PFC to be denser than control FC specimen with the visible image of crowded tiny of cotton shaped (CSH) and few hexagonal plates (CH) contributing to enhanced strength and durability. Conclusively, the foamed concrete containing 30% PSBE as partial cement replacement which exhibits enhanced strength and durability than plain foamed concrete has the potential to be used in construction application. [ABSTRACT FROM AUTHOR]

This paper analyzes the ability of magnesium oxide-based additives to stabilise a low bearing gypsum marly soil, in order to reach subgrade requirements. This soil was not adequate for stabilisation with lime or cement because of its high sulphate content. Binders considered in this investigation were composed of three reactive Mg products and by products, both with and without ground granulated blast furnace slags (GGBS). They were compared to two cements and an aerial lime as soil stabilisers in a laboratory investigation and a field trial. Laboratory tests showed that Mg products with GGBS reached strength results close and at times even better than those of cement. One of the Mg products was the only additive able to reduce the natural soil swelling. Leaching tests demonstrated the ability of the Mg products to reduce the soil leaching of substances like calcium, magnesium, sulphate and chloride. In field trials two of the Mg products combined with GGBS met the bearing capacity requirements for subgrades, in accordance with the Spanish standard. [ABSTRACT FROM AUTHOR]

The head-to-tail cyclic hexapeptide, [cyclo(Val-Thr)3], was found to bind to a range of anions in DMSO-d6 with higher affinity for tetrahedral oxo-anions than halides. 1H NMR spectroscopy indicated that anion binding results in an overall change in peptide conformation with the binding of both sulphate and selenate leading to similar peptide conformations. In the more competitive solvent mixture of 2:8 v/v H2O/DMSO-d6 this cyclic peptide displayed five-fold stronger binding to sulphate than to selenate. [ABSTRACT FROM AUTHOR]

The geotechnical properties of subgrade soils may need to be enhanced for appropriateness in pavement construction using mineral additives such as cement, lime (L) and fly ash. An experimental investigation was undertaken to study the effects of sodium (Na2SO4) and calcium (CaSO4·2H2O) sulphates on pH and pozzolanic reactions of soil–lime–natural pozzolana (soil–L–NP) mixtures in order to choose an adequate mixture for pavement subgrade soil stabilisation. The pH was measured for different curing periods with and without sulphates. The results showed that increases and decreases in pH values depend on the type of additive and its amount, type of sulphate and its content, mineralogical composition of stabilised soil and curing period. In addition, the pH parameter can be used as an indicator to track the pozzolanic reactions process. On the other hand, clayey subgrade soils can be stabilised with Lime–Natural Pozzolana (L–NP) mixtures containing any amounts of CaSO4·2H2O which is highly recommended. However, Na2SO4 with a low content has a better effect on the behaviour of these soils but become deleterious when its content is greater than 2%. In general, the addition of sulphates accelerates both the pozzolanic reactions and NP dissolution. [ABSTRACT FROM AUTHOR]

In this study, a physically and chemically based model including thermodynamic equilibrium, kinetic control and surface complexation is used. Different cases are proposed and simulated with the same set of parameters. The results are compared with experimental data. They show very good agreement between experimental and numerical results. They also show that the parameters are not very sensible to cement composition, concrete mix-design or environmental exposition. Hence, this numerical model seems to be used as a reliable tool to predict the chloride binding capability and external sulphate attack. It is also convenient because of its limited number of parameters. [ABSTRACT FROM AUTHOR]

Burkeite formation is important in saline evaporites and in pipe scales. Burkeite is an anhydrous sulphate-carbonate with an apparent variable anion ratio. Such a formula with two oxyanions lends itself to vibrational spectroscopy. Two symmetric sulphate stretching modes are observed, indicating at least at the molecular level the nonequivalence of the sulphate ions in the burkeite structure. The strong Raman band at 1065 cm−1is assigned to the carbonate symmetric stretching vibration. The series of Raman bands at 622, 635, 645, and 704 cm−1are assigned to the ν4sulphate bending modes. The observation of multiple bands supports the concept of a reduction in symmetry of the sulphate anion fromTdtoC3vor evenC2v. [ABSTRACT FROM AUTHOR]

A total of 42 rain water samples were collected for a period of one year, March 2005 to February 2006, at Jorhat, a rural site of North-East India. The pH of the samples varied from 4.1 to 7.1 with a mean 5.5 showing the acidic nature of rainwater with reference to 5.6 (natural pH of rain water due to CO2 equilibrium in the atmosphere). More than 50% of the rain events have been found to be acidic. Mean concentrations of major ions in the rain water followed the order SO > Ca2+ > NH > NO > PO > H+ > HCO > Na+ > Mg2+ > Cl– > K+ > F–. Ca2+, NH and Mg2+ have shown a neutralization factor less than 1, indicating partial neutralization of anions. EFSoil indicated that soil plays a major role in rain water composition. Maximum concentration for most of the ionic species has been observed during winter followed by summer, post-monsoon and monsoon periods, respectively. Occurrence of acid rain events has been observed throughout the year suggesting that the soil is acidic. [ABSTRACT FROM AUTHOR]

An indolocarbazole dimer with the urea functional group was prepared as an anion receptor which contained eight NH hydrogen bonds donors. Two indolocarbazole units were coupled through a butadiynyl linker to allow for helical folding of the resulting dimer by intramolecular hydrogen bonding and dipole–dipole attractions as proven in the1H NMR spectroscopy. The dimer was found to bind anions (Cl− , Br− , N3− , AcO− ,and) by multiple hydrogen bonds in 10% (v/v) MeOH–acetone, showing high selectivity for sulphate ion. The1H NMR spectra clearly demonstrated that only indolocarbazole NH protons were involved in the hydrogen bonding with small anions such as chloride, but all of the existing indolocarbazole and urea NHs participated in the hydrogen bonding with sulphate ion. This difference in the binding mode might be responsible for the high affinity and selectivity towards sulphate ion. [ABSTRACT FROM PUBLISHER]

Pretreatment methods for measuring stable sulphur (δ34S) and oxygen (δ18O) isotope ratios of dissolved sulphate from watersheds have evolved throughout the last few decades. The current study evaluated if there are differences in the measured stable S and O isotope values of dissolved sulphate from forested watersheds when pretreated using three different methods: Method 1 (M1): adsorb sulphate on anion exchange resins and send directly to isotope facility; Method 2 (M2): adsorb sulphate on anion exchange resins, extract sulphate from anion exchange resins, and send the produced BaSO4 to the isotope facility; and Method 3 (M3): directly precipitate BaSO4 without anion exchange resins with the precipitates being sent to the isotope facility. We found an excellent agreement of the δ34Ssulphate values among all the three methods. However, some differences were observed in the δ18Osulphate values (M1 versus M2:−1.5 ‰; M1 versus M3:−1.2 ‰) associated with possible O contamination before isotope measurement. Several approaches are recommended to improve the pretreatment procedures for δ18Osulphate analysis. [ABSTRACT FROM AUTHOR]

The isotope ratios of various sulphur components (total sulphur content in the sediment, sulphate and H2S in the pore-water) were measured in a number of cores from recent marine sediments taken from the Kieler Bucht (Kiel Bay) region in the western Baltic Sea. Additionally, the quantitative contents of total sulphur, sulphate, sulphide, chloride, organic carbon, iron and water in the sediment and in the pore-water solutions, respectively, were determined. These investigations provided the following results: 1. The sulphur contained in the sediment (∼ 0.3–2% of the dry sample) was for the most part introduced only after sedimentation. This confirms the deliberations of Kaplan et al. [The Distribution and Isotopic Abundance of Sulfur in Recent Marine Sediments off Southern California, Geochim. Cosmochim. Acta 27, 297 (1963)]. The organic substance contributes to the sulphur content of the sediment only to an insignificant degree (in our samples with ∼5–10% of the total sulphur). 2. The sulphate in the pore-waters has been identified as a source for sulphur in the sediment. During normal sedimentation, the exchange of sulphate by diffusion significant for changes in the sulphur content goes down to a sediment depth of 4–6 cm. In this process, the sulphate consumed by reduction and formation of sulphide or pyrite is mostly replaced. The uppermost sediment layer thus represents a partially open system for the total sulphur. The diagenesis of the sulphur is allochemical. At depths below 4–6 cm, we are dealing with a closed system. The further diagenesis of sulphur here is isochemical. 3. The isotope values of the sediment sulphur are influenced primarily by sulphur which comes into the sediment by diffusion and which is bound by subsequent bacteriological reduction as either sulphide or pyrite. As a consequence of the prevailing reduction of 32S and reverse-diffusion of sulphate into the open sea water, a 32S enrichment takes place in the uppermost layer of the sediment. The δ34S values in the sediment range in general between−15 and−35‰, while seawater sulphate is+20‰. No relationship could be established between sedimentological or chemical changes and isotope ratios. In the cores, successive sandy and clayish layers showed no change in the δ34S values. However, the sedimentation rate seems to influence δ34S values. In one core with relatively low sedimentation rates, the δ34S values varied between−29 and−33‰, while cores with higher sedimentation rates showed values between−17 and−24‰. 4. As sediment depth increases, the pore-water sulphate shows, as expected, decreasing concentrations (in a depth of 30–40 cm, we found between 20 and 70% of the seawater values), and increasing δ34S values (in one case reaching more than+60‰). The concentration of sulphide in the pore-water increases, however, with sediment depth (to various extents, reaching 80 mg S per litre in one case). The δ34S values of the pore-water sulphide in all cores show increases paralleling the sulphate sulphur, with a nearly constant δ difference of 50–60‰ in all cores. This seems to confirm the genetic relationship between the two components. [ABSTRACT FROM AUTHOR]