Empirical and mechanistic evaluation of sodium exchange isotherms on natural mineral and organic adsorbents and organically functionalized nanoparticles

This study was conducted to evaluate the efficiency of low-cost adsorbents including bentonite, kaolinite and zeolite saturated with calcium and potassium, potato and wheat residues, and three metal oxide nanoparticles functionalized with an acidic extract of potato residues in improving the quality of sodic waters. The optimization of factors such as pH, contact time, and adsorbent dosage was investigated using a solution containing sodium, calcium, magnesium, and potassium. The optimal pH and contact time were 7.0 and 24 h, respectively. The optimal dosage for using functionalized nanoparticles was 0.1 g and for using other adsorbents was 1.0 g. The sodium exchange isotherms were conducted in binary sodium–calcium and sodium–potassium and quaternary sodium–calcium–magnesium–potassium systems. Zeolite saturated with potassium was the most effective adsorbent in removing sodium from aqueous solutions with an average removal efficiency of 69.2 and 66.5 % in binary and quaternary systems, respectively. Freundlich and Langmuir equations fitted well to experimental data in both binary and quaternary systems. Cation selectivity coefficients calculated based on the Gaines–Thomas convention varied with changing pH and adsorbent dosage. Graphical and statistical evaluations confirmed that the mechanistic cation exchange model using average Gaines–Thomas selectivity coefficients in geochemical PHREEQC program was able to successfully simulate the sodium exchange on different adsorbents in both systems. The Gaines–Thomas selectivity coefficient values greater than unity and as a consequence, the negative values of the Gibbs free energy change of adsorption indicated that sodium exchange reactions in the presence of different adsorbents used is this study were exergonic and spontaneous.     

Correlation between the adsorption of sodium dodecyl sulphate on calcium fluoride (fluorite) and its floatability — An infra-red internal reflection spectrophotometric study

The adsorption of sodium dodecyl sulphate (DSNa) on the surface of calcium fluoride and fluorite was investigated by means of internal reflection spectroscopy in the infra-red range of the spectrum. Samples of calcium fluoride in the form of thin layers evaporated onto the surface of germanium reflection elements, and samples of calcium fluoride and fluorite in the form of finely ground powders were used. As was stated, dodecyl sulphate anions are chemisorbed onto the surfaces of fluoride and of calcium fluoride. Halimondtube flotation experiments showed that a good floatability of calcium fluoride is obtained in the range of concentrations (up to about 1 × 10^?3 mol.dm^?3) where the surface is covered by the chemisorbed product. For concentrations higher than about 1.24 × 10^?3 mol.dm^?3 precipitation of calcium dodecyl sulphate has been observed, accompanied by an abrupt decrease in floatability. The adsorption is greatly affected by the presence of calcium ions and impurities in the solution.     

离子固化剂改性蒙脱土水合-孔隙关联演化机制

以天然钙蒙脱土为研究对象,采用不同浓度的离子固化剂对其进行改性处理,开展素土与改性蒙脱土在相对湿度（P/P0）0～0.95区间的水汽等温吸-脱附试验,通过吸附速率曲线、晶层间距d001值变化曲线分析蒙脱土水合机制,并采用蒙脱土孔隙比变化曲线关联分析水合-孔隙演化规律,提出不同尺度孔隙吸附水的界限相对湿度区间。在此基础上,基于X射线衍射(XRD)、氮气吸附以及压汞试验对离子固化剂改性蒙脱土水合过程的孔隙分布特征进行验证分析。试验结果表明：对于钙蒙脱土,00.8～0.9时,黏土颗粒表面持续吸附弱结合水,此时大孔内逐渐充填水分。离子固化剂通过改变蒙脱土的微观物理化学性质（阳离子与晶层基面）调控其吸附水特性,进而影响不同尺度孔隙的吸附水过程。     

Suitability assessment of shallow and deep groundwaters for drinking and irrigation use in the El Khairat aquifer (Enfidha, Tunisian Sahel)

The El Khairat aquifer is an important groundwater aquiferous system, which is considered a major source for drinking and irrigation water in Enfidha in Tunisian Sahel. The analysis of groundwater chemical characteristics provides much important information useful in water resources management. Assessing the water quality status for special use is the main objective of any water monitoring studies. An attempt has been made for the first time in this region to appreciate the quality and/or the suitability of shallow and deep groundwater for drinking and irrigation. In order to attend this objective, a total of 35 representative water samples were collected during February 2007 from both boreholes (17) and wells (18); and analyzed for the major cations (sodium, calcium, magnesium and potassium) and anions (chloride, sulphate, bicarbonate, and nitrate) along with various physical and chemical parameters (temperature, pH, total dissolved salts, and electrical conductivity). Based on the physico-chemical analyses, irrigation quality parameters like sodium absorption ratio (SAR), residual sodium carbonate (RSC), percentage of sodium (Na%), and permeability index (PI) were calculated. In addition to this, iso-concentration maps were constructed using the geographic information system to delineate spatial variation of qualitative parameters of groundwater samples. The correlation of the analytical data has been attempted by plotting different graphical representations such as Piper, Wilcox, and US Salinity Laboratory for the classification of water. The suitability of the water from the groundwater sources for drinking and irrigation purposes was evaluated by comparing the values of different water quality parameters with World Health Organization guideline values for drinking water. A preliminary hydrochemical characterization shows that most of the groundwater samples fall in the field of calcium–magnesium–chloride–sulphate type of water. Majority of the samples are not suitable for drinking purposes and far from drinking water standards. The high EC value and the percentage of Na in most of the groundwater render it unsuitable for irrigation. Wilcox classification suggested that around 50% of both deep and shallow groundwater samples are unsuitable for irrigation. According to the US Salinity Classification, most of the groundwater is unsuitable for irrigation unless special measures are adopted.     

Characterization of groundwater contamination using factor analysis

 The effluent contamination of groundwater at two industrial sites at Visakhapatnam, India, was studied using factor analysis. Thirty groundwater samples near a zinc smelter plant and 19 from the polymers plant were analyzed for specific conductance, chloride, bicarbonate, sulfate, calcium, magnesium, sodium, and potassium. The data were subjected to R-mode factor analysis and the factor scores transferred to areal maps. While magnesium and sulfate are the dominant contaminants at the zinc site, sodium, chloride, and bicarbonate from the effluent are affecting groundwater in the polymers area. Contour maps for each factor suggest the areal extension of the contaminants. Received: 1 March 1995 · Accepted: 18 September 1995     

Soil chemical changes resulting from irrigating with petrochemical effluents

Irrigating food crops with treated wastewater is a popular management option in India. This study evaluated the impacts of land application of treated petrochemical effluent on soil chemical properties. Soil samples were collected from different depths from sites irrigated with petrochemical effluent for 2?years and from control sites. The effluent collected was analysed for different physic?Cchemical properties and its impact on Lagenaria siceraria (Bottle gourd) growth. 100% concentrated effluent was used for the study and compared with the control. It was observed that application of effluent significantly increased the major cations and anions in the field. On the basis of the study, it may be suggested that treated petrochemical effluent can be used as an alternate source for irrigating crops as it increases the nutrient content of the soil. The overall application indicates a lavishing growth of L. siceraria crop in petrochemical irrigated soil than control sites. This study provides information for better understanding of changes in soil properties due to land application of petrochemical effluent. These changes must be considered in developing possible criteria for preserving delicate ecosystems.     

Vapor-phase interactions and diffusion of organic solvents in the unsaturated zone

This article presents an analysis of the interactions and static movement of 37 organic solvents as vapors through the unsaturated soil zone. The physicochemical interactions of the organic vapors with unsaturated soil materials were emphasized with focus on diffusive, and adsorptive interactions. Fick's Law and porous media diffusion coefficients for most of the solvent vapors were either compiled or estimated; coefficients were not available for some of the fluorinated solvents. The adsorption of some of the solvent vapors by silica was concluded to be due to hydrogen bond formation with surface silanol groups. Heats of adsorption data for different adsorbents were also compiled. There were very few data on the adsorption of these solvent vapors by soils, but it appears that the magnitude of adsorption of nonpolar solvents is reduced as the relative humidity of the vapor-solid system is increased. Consequently, the interaction of the vapors may then separated into two processes; (1) gas-water partitioning described by Henry's Law constants, and (2) solid-water adsorption coefficients which may be estimated from liquid-solid partition coefficients (K _d values).     

A study of groundwater irrigation water quality in south-central Bangladesh: a geo-statistical model approach using GIS and multivariate statistics

Southern Bangladesh’s irrigation and drinking water is threatened by saline intrusion. This study aimed to establish an irrigation water quality index (IWQI) using a geostatistical model and multivariate indices in Gopalganj district, south-central Bangladesh. Groundwater samples were taken randomly (different depths) in two seasons (wet-monsoon and dry-monsoon). Hydrochemical analysis revealed groundwater in this area was neutral to slightly alkaline and dominating cations were Na⁺, Mg²⁺, and Ca²⁺ along with major anions Cl^? and HCO₃ ^?. Principal component analysis and Gibbs plot helped explain possible geochemical processes in the aquifer. The irrigation water evaluation indices showed: electrical conductivity (EC) >750 µS/cm, moderate to extreme saline; sodium adsorption ratio (SAR), excellent to doubtful; total hardness (TH), moderate to very hard; residual sodium bicarbonate, safe to marginal; Kelly’s ratio >1; soluble sodium percentage (SSP), fair to poor; magnesium adsorption ratio, harmful for soil; and IWQI, moderate to suitable. In addition, the best fitted semivariogram for IWQI, EC, SAR, SSP, and TH confirmed that most parameters had strong spatial dependence and others had moderate to weak spatial dependence. This variation might be due to the different origin/sources of major contributing ions along with the influence of variable river flow and small anthropogenic contributions. Furthermore, the spatial distribution maps for IWQI, EC, SSP, and TH during both seasons confirmed the influence of salinity from the sea; low-flow in the major river system was the driving factor of overall groundwater quality in the study area. These findings may contribute to management of irrigation and/or drinking water in regions with similar groundwater problems.     

含盐土水理参数的试验研究

By the indoor experiment research the hydraulic parameters of the saline soil (soil-water potential and coefficient of permeability), find the some characters of the soil- water potential of saline soil: for the same saline soil at the same dry bulk density, whenever salt solution in soil, at the same liquor content the absolute value of the soil-water potential is always bigger than the saltless soil. And at the same liquor content the absolute value of the soil-water potential increases with increasing the concentration of the salt liquor. And at the same concentration of the salt liquor and at the same liquor content, the absolute value of the soil-water potential of sulphate salt liquor soil is bigger than chloride salt liquor soil. Moreover, the absolute value of the soil-water potential of calcium chloride liquor is bigger than sodium chloride liquor. The disciplinarian of the coefficient of permeability to the saline soil is that whenever saline soil the coefficient of permeability decreases with increasing the salt content and the fine soil change more obviously than coarse-grained soil and the sulphate salt soil change more obviously than sodium chloride salt soil.     

The 14-year Performance of a Compacted Clay Liner used as Part of a Composite Liner System for a Leachate Lagoon

The migration of contaminants through a 2.9 m thick compacted clay liner (CCL) for a landfill leachate lagoon is examined 14 years after construction. The clay liner formed the lower portion of the composite liner system but the geomembrane (GM) was found to have defects that had allowed leachate to migrate between the GM and CCL. Chloride, sodium, potassium, calcium and magnesium pore water profiles through the CCL are examined. It is shown that chloride migrated approximately 1.7 m into the CCL during the 14 years of the lagoon operation, sodium approximately 1.2 m, and potassium 0.7 m. Diffusion and sorption data from laboratory diffusion testing are utilized in combination with a finite layer contaminant transport model to predict field contaminant migration profiles through the composite liner system and to establish the time of ‘failure’ of the geomembrane at sometime between 0 and 6 years after installation. Relatively high sorptive uptake of potassium by the CCL soil is observed from batch testing and diffusion testing with field data suggesting an even larger amount of sorption. It is hypothesized that organic sludge matter at the base of the lagoon is responsible for potassium uptake from the leachate. This field case highlights the importance of the compacted clay liner as part of the composite liner system in acting as a diffusion barrier during the lifetime of the lagoon as well as using relatively non-conservative contaminants such as chloride and sodium to estimate geomembrane ‘failure’ times     

A comparative evaluation of groundwater suitability for irrigation and drinking purposes in two intensively cultivated districts of Punjab, India

Punjab is the most cultivated state in India with the highest consumption of fertilizers. Patiala and Muktsar districts are two agricultural dominated districts of Punjab located in extreme south-east and south-west of the state. This paper highlights temporal variations of the groundwater quality and compares its suitability for irrigation and drinking purpose in these two districts. Water samples were collected in March and September 2003, representing the pre-monsoon and post-monsoon seasons, respectively. Water samples were analysed for almost all major cations, anions, dissolved heavy metals and turbidity. Parameters like sodium adsorption ratio, % sodium, residual sodium carbonate, total hardness, potential salinity, Kelley’s ratio, magnesium ratio, index of base exchange and permeability index were calculated on the basis of chemical data. A questionnaire was also used to investigate perception of villagers on taste and odour. Comparison of the concentration of the chemical constituents with WHO (world health organization) drinking water standards of 2004 and various classifications show that present status of groundwater in Patiala is better for irrigation and drinking purposes except for a few locations with a caution that it may deteriorate in near future. In Muktsar, groundwater is not suitable for drinking. Higher total hardness (TH) and total dissolved solids at numerous places indicate the unsuitability of groundwater for drinking and irrigation. Results obtained in this forms baseline data for the utility of groundwater. In terms of monsoon impact, Patiala groundwater shows dilution and flushing but Muktsar samples show excessive leaching of different chemical components into the groundwater leading to the enrichment of different anions and cations indicating pollution from extraneous sources. No clear correlation between the quality parameters studied here and perceived quality in terms of satisfactory taste response were obtained at electrical conductivity values higher than the threshold minimum acceptable value.     

有机污染物(菲)在弱透水层中的越流迁移特征

采用高渗透压渗流试验装置,模拟已被污染的浅层地下水越流通过弱透水层污染深层地下水的过程,研究不同矿化度、不同pH条件下有机污染物（菲）通过饱和黏性土弱透水层时的质量浓度变化特征。结果表明：矿化度的增加有利于弱透水层吸附截留渗滤液中的菲;高矿化度水中的Na+交替土层中的Ca²⁺、Mg²⁺,使水中的Ca²⁺、Mg²⁺质量浓度增加,与HCO^-₃、菲组合形成络合物;不同pH条件下,Ca²⁺、Mg²⁺、HCO^-₃对菲的迁移有阻滞作用,SO^2-₄参与还原反应并可与菲形成络合物,对菲迁移有促进作用。菲在弱透水层中的迁移能力很弱,衰减率达82％～96％,高渗透压下菲的污染锋面迁移速度为0.714 m/d,pH=8时菲通过弱透水层的迁移质量浓度最小。控制渗滤液的pH、组分可有效阻止菲在弱透水层中的迁移。     

Assessment and Modification of Sherard Chemical Method for Evaluation of Dispersion Potential of Soils

Soil dispersion is a phenomenon in which soil particles become afloat when they are exposed to water, and are carried away by the force of seepage. In spite of that soil dispersion is due to its chemical composition, the results obtained from the chemical methods, especially from the most widely used, Sherard method does not match with the results of well-known Pinhole test. This study tries to evaluate and modify the Sherard diagram for determination of dispersion potential of clayey soils. For this purpose, several natural soil samples were collected from different regions of Iran and some artificial soil samples were made by adding different percentages of four chemical agents, including sodium chloride, sodium carbonate, sodium sulfate, and sodium polyphosphate to a natural soil. The physical, chemical and index properties of all samples were determined and for determination of dispersion potential, the commonly used chemical test (Sherard method) and Pinhole test were employed. The results obtained from the tests showed that the Sherard chemical method which is solely based on the amount and type of the existing cations, is not able to determine soil dispersion correctly since the role of some anions, especially chloride is neglected. It was also found that among the existing anions in the soil, the chloride on the contrary to sodium acts as a flocculating factor. The results showed that by converting the vertical axis of the Sherard chart from sodium% to (sodium chloride)%, its conformity to the results of Pinhole tests increases considerably.     

改性石灰粘土固化剂的研究

通过运用正交试验和XRD等方法,研究了改性石灰粘土固化剂的最佳配比及各种外加剂的增强机理,试验表明：对于最佳含水量的土壤,改性石灰粘土固化剂的最佳配比为：生石灰84％,石膏3％,硫酸钠5％,硫酸铝8％。用它固化的土壤州抗压强度比同一条件下用生石灰固化的土壤提高56．9％。外加剂的作用机理在于使稳定土早期形成较多的钙矾石。     

Interaction between groundwater quality and hydraulic head in an area around an underground LPG storage cavern,Korea

The interactive influence between groundwater flow and salinization that occurs in an underground LPG cavern site in Korea was investigated using chemical analysis data and cross-correlation analysis between hydraulic head and operating pressure data. The concentration of the major cations and anions showed a large difference between rainy and dry seasons due to the seasonal intrusion of highly saline water into the cavern area. However, the Cl/Br ratio and '¹⁸O-Cl relationship showed that two types of saline water (seawater and halite-dissolved solution) influenced the groundwater salinization of the study area. The cross-correlation results revealed that a positive relationship between hydraulic head and cavern operating pressure was far more conspicuous in the propane cavern area (89-91% of correlation coefficients), and tidal change influenced the head variation in the butane cavern area. That is, continuous intrusion of seawater near the South Sea could bring about a high concentration of major cations and anions in the butane seepage waters and groundwaters near the coastal area, and seasonal variation in the operating pressure at the propane cavern played an important driving force in fast infiltration of halite-dissolved solution from surface halite stock and a subsequent increase in Na and Cl concentration during the dry season.     

An experimental study on diffusion characteristics of hardened liner materials to inorganic chemicals

For materials of very low hydraulic conductivity used in the landfill liner systems, e.g., natural clay liners, soil-cement liners, etc., diffusion characteristics should be evaluated, as the transport mechanism of contaminant through them is diffusion controlled. Studies on the diffusion characteristics of the hardened liner materials, such as the soil cement, are relatively few compared with those of clayey soils. In this paper, diffusive characteristics of hardened liner materials (HLMs) applied to the liner system of Sudokwon Metropolitan Landfill in Korea, were studied. Laboratory pure diffusion column tests in the pure- and the advection-diffusion status were performed for the chemicals, NaCl, KCl, and CaCl₂. To evaluate the diffusion coefficient of a HLMs system, a one-dimensional numerical transport program was developed for use in a multi-layered HLMs system. The range of dispersion coefficients of advection diffusion column tests was a little narrower than that of diffusion coefficients of pure diffusion tests, although the two coefficients were quite close. The effective diffusion coefficients of chloride ions of a HLMs were about a half of those in clayey soil due to the high density by compaction and curing. Diffusion coefficients of chloride ions in this study were correlated closely with hydraulic conductivities of the materials tested and were consistent with work in the literature.     

水玻璃固化硫酸盐渍土强度特性及固化机制研究

盐渍土化学固化法是解决盐渍土盐胀、溶陷和腐蚀等不良工程问题的有效方法之一。通过无侧限抗压强度试验、X射线衍射试验、化学成分分析和扫描电镜试验研究了石灰粉、煤灰、水玻璃联合固化硫酸盐渍土的强度特征,分析探讨了其固化机制。试验结果表明：石灰含量小于8%时,石灰、粉煤灰、水玻璃联合固化硫酸盐渍土的抗压和抗剪强度较石灰粉煤灰固化土有大幅度提升,固化土强度随水玻璃浓度几乎呈线性增长。水玻璃固化硫酸盐渍土强度增加的机制在于：水玻璃的碱激发粉煤灰作用和水玻璃与盐渍土中化学成分的吸附作用所生成各类凝胶的填充和包裹,使得骨架颗粒的接触面积增大,颗粒之间的孔隙逐步减小,骨架颗粒由点接触变为面接触,固化盐渍土通过凝胶而黏结成为一个紧密的空间网状整体结构,土体强度得以提高。同时,复杂的物理化学作用大幅度降低了固化盐渍土中 含量,有效地抑制了硫酸盐渍土的盐胀特性。     

Groundwater quality in the coastal stretch between Sirkazhi and Manampandal, Tamil Nadu, India using ArcGIS Software

An attempt has been made in this research paper to understand the groundwater quality of coastal stretch from Sirkazhi to Manampandal of Nagapattinum district, Tamil Nadu (India). A total of 47 samples were taken for the baseline study. The water samples collected in the field were analyzed for electrical conductivity, pH, total dissolved solids (TDS), major cations like calcium, magnesium, sodium, potassium, and anions like bicarbonate, carbonate, chloride, nitrate, and sulfate, in the laboratory using the standard methods given by the American Public Health Association. The groundwater locations were selected to cover the entire study area and attention was given to the area where contamination is expected. The expected groundwater contaminants were chloride, nitrate, TDS, Na, and K. The results were evaluated in accordance with the drinking water quality standards given by the World Health Organization. To know the distribution pattern of the concentration of different elements and to demarcate the higher concentration zones, the contour maps for various elements were also generated, discussed, and presented.     

A geochemical assessment of coastal groundwater quality in the Varahi river basin, Udupi District, Karnataka State, India

The Varahi Irrigation project site is located at 13°39′15″N (latitude) and 74°57′E (longitude) in Hole Shankaranarayana village, approximately 6 km from Siddapura, Kundapura taluk, Udupi district. A total of 59 groundwater samples were collected from dug and tube wells in November 2008 to evaluate hydrochemistry and suitability for drinking and irrigation purposes. The physico-chemical parameters estimated include pH, electrical conductivity (EC), total dissolved solids (TDS), redox potential (Eh), total hardness (TH), total alkalinity (TA), temperature, major cations and anions, besides irrigation quality parameters like boron, sodium absorption ratio (SAR), % Na, residual sodium carbonate (RSC), residual sodium bicarbonate (RSBC), chlorinity index, soluble sodium percentage (SSP), exchangeable sodium ratio (ESR), non-carbonate hardness, potential salinity (PS), permeability index (PI), Kelly index (KI), magnesium hazard (MH), magnesium ratio (MR), index of base exchange. Chloride, sulphate and bicarbonate concentrations classified the groundwater samples into normal chloride, normal sulphate and normal bicarbonate water types, respectively. The Salinity (Class I; 98.3%), Chlorinity (Class I; 100%) and Sodicity (Class 0; 96.6%) indices suggest the suitability of groundwater for irrigation. The Wilcox diagram illustrates that 96.6% of the samples belongs to excellent to good category, while the US Salinity Laboratory (USSL) diagram indicates the low salinity/low sodium content in 86.44% of samples (C1S1). Positive index of base exchange in majority of the samples (91.52%) indicates direct base exchange reaction or chloro-alkaline equilibrium in the study area. The positive value of RSC in majority of samples signifying higher concentrations of HCO₃ over alkaline earths indicates that groundwater are base exchange-softened water as there is an exchange of alkaline earths for Na⁺ ions. Majority of water samples fall in the precipitation dominance field based on Gibbs’ ratio.     

Interactions Between Soils and Laboratory Simulated Electrolyte Solution

To study the impact of salt water intrusion on two types of soils from west coast region of India were investigated in the laboratory. The key characteristics evaluated included Atterberg limits, compaction characteristics, hydraulic conductivity and chemical characteristics of selected soils. The sea at this coast receives effluent from different points and hence the characteristics change with time and locality. Therefore, to maintain uniform composition, 0.5 N sodium chloride solution (NaCl) was prepared in the laboratory and batch tests were used to determine the immediate effect on soils. Soil specimens were prepared by mixing the soils with 0.5 N NaCl in the increments of 0, 5, 10 and 20% by weight to vary the degree of contamination. Experimental results of soils mixed with 0.5 N NaCl showed that the maximum dry density increases and the optimum moisture content (OMC) decreases with increasing sodium chloride concentration. The study also revealed that the hydraulic conductivity of the soils tested increases with increase in sodium chloride concentration. The Atterberg limits of contaminated specimens show a remarkable change when compared with uncontaminated specimens.