Study of Sulphatizing Roasting Process Using Iron Sulphates for the Treatment of Zinc Leach Residue

The paper presents the results of the investigation of zinc leach residue (ZLR) processing by sulphatizing roasting with iron sulphates FeSO4 and Fe2(SO4)3 followed by water leaching. The elemental and phase compositions of ZLR of JSC "Chelyabinsk Zinc Plant" were studied. Based on the thermodynamic calculations using HSC Chemistry 9.9 software, the temperature ranges of the sulphatizing roasting and the required amounts of iron sulphate additives for the sulphation of zinc and copper were determined. Subsequent experiments showed that recovery rates of zinc and copper reached 99.5% and 89.1% respectively, while iron remained in the leached residue. The results have indicated a high efficiency of sulphatizing roasting to transform zinc and copper contained in ZLR from ferrite to water-soluble sulphate.

Characteristics of the acidity and sulphate fractions in acid sulphate soils and their relationship with rice yield

SUMMARYMost acid sulphate soils (ASSs) in the Pearl River Delta of South China have been traditionally reclaimed for rice cultivation, but the rice yield in most of these paddy fields is lower than the average rice yield in China due to extremely high soil acidity. In the present study, a range of sulphate and acidity parameters were investigated in ASS profiles in three types of paddy fields in Taishan City (Guangdong Province, China) divided based on the local rice productivity (4500, 3000 and 1500 kg/ha) using an abandoned ASS (uncultivated) as the control treatment to ascertain key yield constraining parameters. Soluble acidity (SA), exchangeable acidity (ExA), soluble sulphate (SS) and net acid-soluble sulphate (NAS) increased with increasing soil depths from 0 to 100 cm and then decreased abruptly with further increases in the depth. However, the depth distribution of exchangeable sulphate (ES) was uniform. The soil acidity and sulphate contents differed significantly in three sampled paddy fields. The values of SA and SS in the soils at depths of 0–100 cm in the studied ASS were lower compared with those in the uncultivated ASS and the ExA in soils at depths of 0–40 cm in ASS were lower compared with those observed in the uncultivated ASS. A correlation analysis revealed that SA was strongly correlated with SS and ExA with NAS. Soluble acidity, ExA, SS and NAS in the ASS were significantly associated with rice yield. Exchangeable acidity in the plough layer (0–20 cm) of soils was the most sensitive indicator of soil quality affecting rice yield among those in soils from 0 to 140 cm depth. It is interesting to note that SA, SS and NAS were more sensitive indicators of soil quality affecting rice yield at 60–100 cm than at 0–40 cm depth. Principal component analysis showed that pH value, ExA and ES in soils at depths of 0–40 cm and SA, SS and NAS in soils at depths of 60–100 cm constituted the critical soil acidity and sulphate characteristics that were strongly correlated with rice yields. This finding implies that controlling the ExA in the plough layer and the SA and NAS in the Jarosite layer should be the major focus of studies aimed at the amelioration of ASSs.

Determination of sulphur species in solidified cryolite melts

Solidified cryolite melts containing a known amount of Na2SO4 (0–713 mg kg−1 SO42−), Na2S, FeS, and CdS (0–400 mg kg−1 S2−) together with industrial electrolyte samples were tested for the content of sulphate and sulphide ions by ion chromatography. Added and analytically determined contents of sulphate and sulphide were compared and processed by means of linear regression analysis. It was found that the method of ion chromatography yields satisfying results (uncertainty below 1.1 %) and that it is especially suitable for the determination of low content of soluble sulphate or sulphide in solidified cryolite electrolytes. The method can be used for the estimation of insoluble sulphide content in cryolite melts as well. Results of industrial samples analysis showed that the content of sulphate and sulphide in the samples is influenced by their treatment before the analysis.

The extraction of intracrystalline biomarkers and other organic compounds from sulphate minerals using a microfluidic format – a feasibility study for remote fossil-life detection using a microfluidic H-cell

Water-soluble sulphate minerals such as epsomite and gypsum have been reported on a number of planetary bodies of astrobiological interest and their presence is often used as an indicator for potential habitability as it can indicate the presence of liquid water. The sulphate minerals can incorporate biomarkers and biomolecules as intracrystalline inclusions. These intracrystalline inclusions are protected from their exterior chemical environments and their analysis can yield a biomarker record, even in environments where extreme oxidizing conditions may have degraded any record present in non-intracrystalline organic matter. In this study, organic compounds were incorporated within epsomite as intracrystalline inclusions by co-precipitating a mineral from solutions of a mineral and organic compound. A feasibly study utilizing a microfluidic H-cell to process finely ground samples of the inclusion-bearing epsomite indicates that a similar device may be used to extract biomarkers for analysis.

Recovery of chemical and physical properties of boreal plain soils impacted by pipeline burial

Pipeline construction on the Canadian boreal plain occurs on woodland and/or agricultural fields, but soil recovery from its impact is not well documented. Therefore, we quantified changes over 3 yr (1992 to 1994) in the chemical properties of two Grey soils and the physical properties of a Grey soil that were subjected to pipeline burial and cropped to barley. The pipeline right-of-way (RoW) was divided into three zones: a road (or work) area used for vehicular traffic, a trench area for burying pipeline, and a pile (or spoil) area where soil was stockpiled during excavation. Pipeline construction resulted in mixing of subsoil material with topsoil, and the chemical properties most affected were those that varied most with depth. The pH, electrical conductivity, soluble sulphate, and exchangeable Ca and Na were increased in the surface 20 cm of soil, particularly the road and trench areas. The affected properties moderated 2 or 3 yr after pipeline construction as soluble components were dissolved or dispersed and translocated back to lower soil depths. The RoW zones had increased soil strength and compaction, and reduced water retention and infiltration rates. However, the deterioration in soil physical condition was similar across the RoW zones, indicating that it was due mainly to land clearing, a requirement to convert woodland to agricultural land. Improvement in bulk density, and water infiltration and retention in 1993 and 1994 indicated that the RoW was undergoing rehabilitation with time as a result of natural processes and annual cropping. Key words: Chemical properties, exchangeable cations, sulphate, physical properties, soil-water, pipelines

Development of sunny-facing high country using different forms of sulphur fertiliser

Different forms and rates of sulphur (S) fertiliser were examined for developing oversown tussock in sunny-lying South Island high country. Sulphur significantly increased dry matter (DM) production (p = 0.0001). Soluble forms of S were most effective in the first year, and lasted 15-18 months. Sulphur bentonite prills took 6 months to be effective, but over time the higher rate (56 kg S/ha) was one of the better treatments. Elemental S on its own was ineffective even after 3 years. The combination of soluble sulphate and finely divided elemental S (56 kg S/ha as sulphur super extra) was the most effective treatment. In the first 2 years alsike clover was the most dominant pasture species. Native grasses became dominant in the third year. After retopdressing at the beginning of year 4, pasture production again improved, particularly in those treatments containing only soluble forms of S. White clover was the dominant pasture species in the fourth year. Sulphur significantly increased soil-available nitrogen levels (p = 0.0001). Keywords development, sunny hill country, sulphate sulphur, elemental sulphur, sulphur super extra, sulphur bentonite prills, available nitrogen

APPLICATION OF A SEQUENTIAL EXTRACTION PROCEDURE TO THE DETERMINATION OF THE DISTRIBUTION OF SULPHUR FORMS IN SELECTED PEAT MATERIALS

Total S (St), soluble sulphate, pyritic S, elemental S, carbon-bonded S (C-S) and organic sulphate S were determined on four peat samples and three sedimentary gyttja samples, one of which (Ginc.) had been subjected to aerobic incubation. A sequential extraction procedure was used to assess the distribution of St and of organic S forms in a series of peat fractions. Total S varied from 0.42 to 3.67%, with values below 1% associated only with freshwater-derived peats. The S content of brackish peat and of gyttja was consistently high and in some cases, organic S exceeded 6% of the organic matter. With the exception of Ginc., organic S accounted for a very high proportion of St (mean 94%), with C-S the dominant organic S form. Ginc. showed a very different S form distribution from the unincubated gyttja samples, with organic S accounting for only 44.5% of St, and organic sulphate-S exceeding C-S. Ginc. also had a lower pH, suggesting acidification resulting from oxidation of the organic C-S fraction during incubation. The recovery of St in seven peat (or gyttja) fractions averaged 99%, and indicated that humic acid and residue ("humin") fractions together generally accounted for most of the organic S (73.3–90.4%), with the notable exception of Ginc., for which these fractions only accounted for 42–47% of organic S. The proportion of humic acid-S increased with increase in degree of peat decomposition. The fulvic acid fraction contained variable proportions of St and had relatively more oxidized S forms than humic acid or residue fractions. Some oxidation of C-S occurred during alkaline extraction. Minor amounts of organic S were extracted with water, chloroform and ethanol-benzene. Key words: Sulphur forms, peat sulphur, gyttja, peat fractions

Evaluation of the sulphur status of some grasses for silage in Northern Ireland

Seventy-five grass samples for first-cut silage and 131 samples for second-cut silage were collected in 1983 from intensively managed farms with coarse-textured soils. Samples with total sulphur less than 2·0 g/kg or Kjeldahl nitrogen greater than 28 g/kg, together with nitrogen to sulphur ratio greater than 14, and adequate phosphorus and potassium, were selected as suboptimal in sulphur. The extent of sulphur deficiency was assessed using water-soluble sulphate values of 300–500 and 200–300 mg S/kg to indicate yield depressions of less than 5 and 10% respectively. In the first cut, 20 and 8% of sites were likely to have suffered yield depressions of less than 5 and 10% respectively. Soil-extractable sulphate values less than 10 mg S/kg indicated marginal sulphur reserves for second-cut silage at 49% of the sites. Grass analyses of the second-cut samples showed that 11 and 3% of the sites were likely to have suffered yield depressions of less than 5 and 10% respectively. Incidental sulphur inputs from deposition, organic manures and mineralization may have obviated much of the potential sulphur deficiency for second-cut grass.