Cation Exchange Of Na Research Articles

A modified zeolite (Na2SO4 @zeolite NaA) as a novel adsorbent for radium-226,228 from acidic radioactive wastewater: Synthesis, characterization and testing

The radiological contamination with radium in oil and gas production is challenging environmental and health concerns. This study investigated the synthesis of zeolite NaA modified with Na2SO4 (Na2SO4@zeolite NaA) hydrothermal method and subsequent use as an adsorbent along with manganese dioxide (MnO2) for removing radium isotopes (226Ra and 228Ra) from acidic radioactive wastewater (ARW). ARW was generated through acidic sequential leaching of petroleum-based organic soils collected from the South Rumaila fields in the Basra Governorate, Iraq. The optimum adsorption parameters were MnO2: Na2SO4@zeolite NaA mass ratio of 1:0.5 g.g−1 and a pH of 6.3 resulting in maximum removal of 78.7% and 66.7% for 226Ra and 228Ra, respectively. Higher levels of removal were not attainable due to co-elements effect. The adsorption was endothermic with cation exchange of Na+ with Ra2+ being the main mechanism. The incorporation of Na2SO4 increased the exchange sites available for Ra2+ and the surface area and pore size available for facilitating such reactions. The exhausted column was regenerated and subsequently used for five cycles with a small drop in the removal of 226Ra and 228Ra by 11% and 9.5%, respectively highlighting the propitious application of Na2SO4@zeolite NaA and MnO for treating contaminated wastewater in oil fields.

Destruction of groundwater quality and the risk of saltwater intrusion in the aquifers nearby Sirjan salt playa, Iran

ABSTRACTThis research investigated on the hydrochemistry and salt-fresh mixing of the groundwater in the aquifers nearby Sirjan salt playa near Sirjan city, Kerman province, Iran. Therefore, 62 groundwater samples were collected from Sirjan salt playa, Kheyrabad plain, Chahderaz plain and Golgohar mining area. Chemical diagrams, ion ratios, statistical method and mixing applied to hydochemical investigation. The water samples were then categorised into four water types; i.e. NaCl, Na-Ca-Cl, Na-SO4 and Ca-HCO3. The presence of salt playa in the area has led to the phenomenon of mixing between saline and freshwater. Saltwater intrusion occurred from 0.01 to 29% in the groundwater and it destroyed the quality of groundwater in the study area. Most percentages of intrusion were seen in Golgohar mine area and which is due to overexploitation of groundwater by dewatering process in the pit, where the saltwater intrudes from hard rock aquifer by upconing phenomena. Results showed that the actual concentrations of Na+ are less than expected concentrations; while for Mg2+ and Ca2+ their actual concentrations have been increased versus expected concentrations and it suggests cation exchange of Na+ by Mg2+ and Ca2+ in the aquifers of the study area.

Influence of Na+ content on the structure and morphology of TiO2 nanoparticles prepared by hydrothermal transformation of alkaline titanate nanotubes

ABSTRACTThe objective of this study is to investigate the role of Na+ content in the morphology evolution of TiO2 nanoparticles prepared by hydrothermal approach. Various TiO2 morphology from 0-dimensional (0D) nanoparticles to 1-dimensional (1D) nanorods were synthesised by hydrothermally treating the alkali titanate nanotubes with different Na+ content. The XRD patterns show the phase transformation and crystallographic nature of alkali titanate nanotubes are strongly dependent on the Na+ content, the cation exchange of Na+ by H+ ion exchange affects the crystallinity of the tubes and causes disorder of the interlayers of nanotubes. The SEM and TEM images confirm that Na+ rich titanate nanotubes were thermally stable. Moreover, BET measurements revealed that the Na+ content plays an important role on the specific surface area of formed TiO2 nanoparticles. The photocatalytic activity of the TiO2 nanoparticles was characterised via the decomposition rate of an aqueous solution of methyl orange (MO) under UV light irradiation. The TiO2 nanoparticles prepared by hydrothermally treating the alkali titanate nanotubes with no Na+ content has a surface area of 55.1 m2/g with nearly 100% photodecomposition of MO in 20 min.

THE ION-EXCHANGE PROPERTIES OF NATURAL ZEOLITE MORDENITE

The cation exchange properties of mordenite (a Nakhchivan natural zeolite) were studied. Ion exchange of the original cations - sodium, potassium and calcium - by magnesium, strontium, cadmium, zinc and nickel cations was carried out. It was found that in the case of Zn cations cation exchange occurs readily at a high speed and the maximum value of the degree of exchange. A low value of the degree of cation exchange is observed for Mg. This is due to the large hydration shell of magnesium, which adversely affects the cation exchange. High values of the exchange rate of Na+ cations have already been explained at the first exchange of low content of sodium cations and their location mostly in exchange for positions available. The lesser ability to exchange K+, Na+ cations than contained in the natural zeolite is due to several reasons. With an increasing number of degrees of ionic exchange value exchangeable cations K+ vary to a greater degree than the degree of exchange of the cations Na+. Firstly, the content and size of the K+ cation are greater than those of the Na+ cations. Furthermore, a part of the K+ cations is in exchange for hard cancrinites cells. It has been found that the degree of cation exchange of K+ (αK), contained in the original zeolite, with Mg2+, Ni2+, Sr2+, Zn2+, Cd2+ cations is considerably lower than the values of the degree of cation exchange of Na+ (αNa) at the same cations.

Polymericaly modified clays to preparation of polystyrene nanocomposite by nitroxide mediated radical polymerization and solution blending methods

Polymericaly modified clays that contain an oligomeric poly(styrene‐co‐chloromethyl styrene) ammonium salt have been prepared and used to preparation of polystyrene (PS) nanocomposites. First, PS and poly(styrene‐co‐chloromethyl styrene) [P(St‐co‐CMSt)] were synthesized by nitroxide mediated living free radical polymerization (NMRP) by TEMPO iniferter .Then the copolymer was coupled with N, N‐dimethyl hexadecyl amine to prepare polymeric modifier by anion exchange of chlorine group of chloromethyl styrene (CMSt) by quaternary amine. The synthesized polymeric modifier was mixed with nanoparticle of silica to change the property of clay surface from hydrophilic to hydrophobic via cation exchange of Na+ with alkylammonium ions. For synthesizing of nanocomposites, we used polymericaly modified montmorillonite and PS that was synthesized by NMRP technique. Intercalated nanocomposites and in some cases, exfoliated or mixed intercalated/exfoliated nanocomposites of all of these polymers have been produced by solution blending method. The prepared materials were characterized by X‐ray diffraction, Transmission electron microscopy, Fourier‐transform infrared, 1H nuclear magnetic resonance, and gel permeation chromatography techniques. Effect of layered silicates on thermal properties and glass transition temperature of PS was investigated using TGA and DSC techniques. POLYM. COMPOS., 38:1127–1134, 2017. © 2015 Society of Plastics Engineers

Hydrogeochemistry of Dal Lake and the potential for present, future management by using facies, ionic ratios, and statistical analysis

This paper presents the inventory study on the Dal Lake, the second largest fresh water lake in Kashmir Valley, India. A total of 336 water samples were monthly collected to assess the present scenario of weathering and anthropogenic impact on water for hydrological year (2012–2013). The results showed a significant spatio-temporal (monthly and basinal) variability in the concentration of the physical and chemical characteristics (major ions) of the lake water. The lake water is alkaline in nature (pH: 7.1–8.7) characterized by medium total dissolved solids of 80.8–230.7 mg L−1 and electrical conductivity of 126.3–384.6 µs cm−1. The order of major cations and anions is Ca2+ > Mg2+ > Na+ > K+ and HCO3 > SO42− > Cl− > NO3−, respectively. The geochemical processes suggested that the lake water composition is mostly influenced by the lithology of the catchment. Ca–Mg–HCO3 was found to be the dominant hydrochemical facies followed by mixed type of water (throughout the hydrological year). From sub-basin point of view all the four basins show Ca–Mg–HCO3 type water, but Hazratbal and Nigeen basins also show shift towards SO4 and Cl type of water reflecting the anthropogenic inputs in these two basins. Basin wise the average concentration of Ca2+, Mg2+, HCO3−, Cl−, and NO3− were highest in Nigeen basin due to high resistance time of water within the basin and Na+, K+, and SO42− in Hazratbal basin from the silicate weathering, and sewage plant sources. The Gagribal basin showed lowest values of Ca2+, Na+, K+, HCO3−, and Cl−, whereas Boddal and Hazratbal basin showed lowest values of SO42−, NO3−, and Mg2+, respectively. On monthly basis Ca2+, Na+, K+, and HCO3− were highest in April, Mg2+, and NO3− in January, Cl− in December and SO42− in September, lower value of Ca2+, and Cl− were observed in July, Mg2+ in April and HCO3−, and K+ in August. The study suggested that the predominant processes influencing water chemistry were congruent carbonate dissolution (61.9 %) and incongruent silicate weathering (12.7 %) and cation exchange of Na+ in rocks for Ca2+ and Mg2+ (10 %). The high major-ion concentrations indicated long water–rock interactions and long residence time of water in the lake. The higher concentrations SO42−, NO3− and Cl− reflect anthropogenic inputs from the immediate catchment.

English

  This study was conducted on the hydrochemistry of shallow groundwater and surface water in the Ndop plain, North West Cameroon. The objectives were to determine the physico-chemical characteristics of water, controls on water chemistry and suitability for drinking and irrigation. Forty-six shallow groundwater and 26 surface water samples were investigated. Field measurements of physical parameters were preceded by chemical analyses of the samples for major ions and F-. About 69% of the water sources had pH values below 6.5, classifying the water as barely acidic. Electrical conductivity (<282 µS/cm) and total dissolved solids (<183 mg/l) were low suggesting low-mineralised and freshwater. The relative abundance of major ions (meq/l) was Na2+>Ca2+>Mg2+>K+ for cations and HCO3->>NO3-≥Cl->SO42- for anions. Major ion concentrations were low, and within the WHO guidelines for drinking water, but F-concentrations were much lower (<0.39 mg/l) and below guideline value. Main water types and proportions were Na-HCO3 (53 %), Ca-HCO3 (35 %) and a mixed Na-Ca-HCO3 (11%). Predominant processes influencing water chemistry were incongruent dissolution of silicate minerals and cation-exchange of Na+ in rocks for Ca2+ in water. The low major ion concentrations indicated low water-rock interactions and short residence time. The analysed water was suitable for irrigation.   Key words: Water chemistry, hydrochemical controls, drinking-irrigation quality, Ndop plain, Cameroon.

Impact of anthropogenic and natural processes on the evolution of groundwater chemistry in a rapidly urbanized coastal area, South China

The moving of manufacturing industry from developed countries to Dongguan, China, promoted the semi-urbanization and rural industrialization in this area. It is urgent to acquire the impact of the enhanced anthropogenic pressure on the evolution of groundwater chemistry in this area. The objectives, in this study, were to understand the evolution of groundwater chemistry in Dongguan area based on the comparison of hydrochemical data variations and land use changes during the urbanization, to distinguish the impact of natural processes and anthropogenic activities on the groundwater chemistry by using principal components analysis (PCA) and hierarchical cluster analysis (HCA), and to discuss the origins of trace elements in groundwater. Eighteen physico-chemical parameters were investigated at 73 groundwater sites during July 2006. By analyzing the hydrochemical data, it shows that lateral flow from rivers and agricultural irrigation are the mechanisms controlling the groundwater chemistry in the river network area where the cation exchange of Na+ in sediments taken up by the exchanger Ca2+ occurs. Seawater intrusion is the mechanism controlling the groundwater chemistry in the coast area where the cation exchange of Ca2+ in sediments taken up by the exchanger Na+ occurs. The ion exchange reaction for fissured aquifer is weak in the study area. In addition, the comparison of hydrochemical data between in 2006 and in 1980 shows that anthropogenic activities such as excessive application of agricultural fertilizers, inappropriate emissions of domestic sewage and excessive emissions of SO2 are responsible for the occurrences of groundwater with NO3−, SO42− and Mg2+ types. Four principal components (PCs) were extracted from PCA, which explain 80.86% of the total parameters in water chemistry: PC1, the seawater intrusion and As contamination; PC2, the water–rock interaction, surface water recharge and acidic precipitation; PC3, heavy metal pollution from industry; and PC4, agricultural pollution and sewage intrusion. Four clusters were generated from HCA: cluster 1 is mainly influenced by the industrialization; cluster 2 is mainly affected by the water–rock interaction and the irrigation and lateral flow of river water; cluster 3 is mainly influenced by the seawater intrusion; and cluster 4 is mainly influenced by the sewage intrusion and agricultural pollution. The results show that both natural processes such as seawater intrusion, water–rock interaction and lateral flow of river water and anthropogenic activities such as industrialization, sewage intrusion and agricultural pollution are the two major factors for the evolution of groundwater chemistry in Dongguan area.

Pickering Emulsion as a Template to Synthesize Janus Colloids with Anisotropy in the Surface Potential

A versatile new concept is presented for the synthesis of Janus colloids composed of Laponite nanoclay armored poly(divinylbenzene) with an anisotropic surface potential via a double Pickering emulsion template. First, polystyrene or poly(divinylbenzene) colloids stabilized with Laponite nanoclay are synthesized via a Pickering miniemulsion approach. These nanoparticle-stabilized colloids were then templated at a wax-water interface in a second Pickering emulsion in order to chemically modify one hemisphere of the colloids. Janus modification of the colloids was accomplished by cation exchange of sodium ions, originally present on the surface of the Laponite with various salts of modifying ions (Ca(2+), Fe(2+), and Fe(3+)) in the suspension. The zeta potential of the chemically modified and unmodified colloids was compared. The maximum change in the zeta potential was given by the calcium ions, Ca(2+)-adsorbed modified colloids as compared to unmodified sodium ions, Na(+)-adsorbed colloids. The distribution of charges on the Janus colloids results in a nonuniform zeta potential. XPS and optical microscopy were used to verify the successful chemical modification by the cation exchange of Na(+) for Ca(2+) ions on one hemisphere of the Janus colloids.

Hydrogeochemistry of groundwaters in a semi-arid region. El Ma El Abiod aquifer, Eastern Algeria

In this work, we present results of the hydrogeochemical and isotopic studies on groundwater samples from the El Ma El Abiod Sandstone aquifer, in Tebessa, Algeria. Chemical and environmental isotope data are presented and discussed in order to identify the geochemical processes and their relation with groundwater quality as well as to get an insight into the hydrochemical evaluation, in space and time, of groundwater and of the origin of dissolved species. A combined hydrogeologic and isotopic investigation have been carried out using chemical and isotopic data to deduce a hydrochemical evaluation of the aquifer system based on the ionic constituents, water types, hydrochemical facies, and factors controlling groundwater quality. All of the investigated groundwaters are categorized into two chemical types: low mineralized water type and relatively high mineralized water type. Interpretation of chemical data, based on thermodynamic calculations and geochemical reaction models of selected water groups constructed using PHREEQC, suggest that the chemical evolution of groundwater is primarily controlled by water–rock interactions, involving (1) acidic weathering of aluminosilicates, (2) dissolution of secondary carbonate minerals, and (3) cation exchange of Na+ for Ca2+. However, the original composition of groundwater may have been modified by further secondary processes such as mixing of chemically different water masses. The combined use of SI and mass-balance modeling has shown to be a useful approach in interpreting groundwater hydrochemistry in an area where large uncertainties exist in the understanding of the groundwater flow system. Interpretation of 18O and 2H, suggest that the recharge of the investigated groundwaters may result from different mechanisms.

Understanding the salinisation process for groundwater in an area of south-eastern Australia, using hydrochemical and isotopic evidence

Increases in groundwater salinity down gradient are a common occurrence in catchments throughout Australia, exacerbating the effects of dryland salinisation in discharge areas. Groundwater hydrochemical and isotopic data from the Willaura catchment in south-eastern Australia, which is affected by both primary (natural) and secondary (human-induced) salinity, allowed the factors that cause the down gradient trend in salinisation within this catchment to be determined. The overall salinity of the groundwater (0.8–70 mS/cm) is controlled by evapotranspiration, which concentrates cyclic salts in the unsaturated zone, greatly increasing the salinity of the soil–water to 3700–6400 mg/L Cl −. The progressive addition of this saline soil–water to fresher groundwaters recharged on the catchment margins causes a gradual increase in salinity down gradient. The groundwater stable isotope compositions show that most recharge occurs in winter and spring. Groundwater salinities increase around the saline lakes of the discharge zone, due to direct evaporation from shallow watertables and minor dissolution of halite (as indicated by Cl −/Br − ratios). Mineral–water interactions within the aquifers cause a slight overall reduction in salinity; conversion of kaolinite to smectite and illite, and cation exchange of Na + for Ca 2+ on smectites, cause Na +/Cl −, Mg 2+/Cl −, K +/Cl −, Si/Cl − and HCO 3 −/Cl − ratios to progressively decline and pH to gradually increase down gradient. Oxidation of organic matter causes a strong decrease in the redox potential of the groundwaters down gradient. The groundwater ages increase from modern (containing tritium) on the catchment margins to ∼8000 years (based on 14C dating) at the end of the ∼25 km flow path. The older groundwaters are isotopically heavier than the younger waters, probably due to recharge during a wetter climate in the early Holocene. The groundwater ages show clearly that the progressive addition of saline soil–water, causing groundwaters to become more saline down gradient, has occurred throughout the Holocene and may explain the occurrence of primary salinisation within many Australian catchments.

Revised preparation procedure of calcium hydroxyapatite with sol consisting of sodium alginate and sodium diphosphate

Calcium hydroxyapatite (Ca10(PO4)6(OH)2; CaHAp) was prepared from the cation-exchange of Na+ in the gel consisting of sodium alginate and Na4P2O7 with Ca2+ from the mixture of Ca(CH3COO)2 and Ca(NO3)2 in an aqueous solution at pH 10 although it had been already reported that CaHAp could be prepared with the employment of CaCl2 at pH 6.5, which rather afforded calcium chlorapatite (Ca10(PO4)6Cl2).

PH neutralization and zonation in alkaline-saline tank waste plumes.

At the Hanford Site in Washington State, the pH values of contaminant plumes resulting from leaking of initially highly alkaline-saline radioactive waste solutions into the subsurface are now found to be substantially neutralized. However, the nature of plume pH neutralization has not previously been understood. As a master geochemical variable, pH needs to be understood in order to predict the fate and transport of contaminants carried by the waste plumes. Through this laboratory study, we found that the plume pH values spanned a broad range from 14 (within the near-source region) down to the value of 7 (lower than the pH value of the initial soil solution) while the plume was still connected to an actively leaking source. We defined two zones within a plume: the silicate dissolution zone (SDZ, pH 14-10) and the neutralized zone (NZ, pH 10-7). Quartz dissolution at elevated temperature and precipitation of secondary silicates (including sodium metasilicate, cancrinite, and zeolites) are the key reactions responsible for the pH neutralization within the SDZ. The rapid and thorough cation exchange of Na+ replacing Ca2+/Mg2+, combined with transport, resulted in a dynamic Ca2+/Mg2+-enriched plume front. Subsequent precipitation of calcite, sodium silicate, and possibly talc led to dramatically reduced pH within the plume front and the neutralized zone. During aging (after the plume source became inactive), continued quartz dissolution and the secondary silicate precipitation drove the pH value lower, toward pH 11 at equilibrium within the SDZ, whereas the pH values in the NZ remained relatively unchanged with time. A pH profile of 11 from the plume source to pH 7 at the plume front is expected for a historical plume. This laboratory-based study provided realistic plume pH profiles (consistent with that measured from borehole samples) and identified underlying mechanisms responsible for pH evolution.

Geochemistry, origin and recharge mechanisms of groundwaters from the Garoua Sandstone aquifer, northen Cameroon

This paper presents results of the geochemical and isotopic studies on groundwater samples from the Garoua Sandstone Basin, in northern Cameroon. Chemical and environmental isotope data are presented and discussed in terms of the origin of dissolved species and of groundwater. All of the investigated groundwaters are categorized into two chemical types: low mineralized and acidic waters of CaNaHCO 3 type, and relatively high mineralized waters of NaHCO 3 type, with relatively high pH, between 7.40 and 8.22. Interpretation of chemical data, based upon both thermodynamic calculations and stability diagrams, suggests that the chemical evolution of groundwater is primarily controlled by water-rock interactions, involving (1) acidic weathering of aluminosilicates, (2) dissolution of secondary carbonate minerals, and (3) cation exchange of Na + for Ca 2+. However, the original composition of groundwater may have been modified by further secondary processes such as mixing of chemically different water masses, and anthropogenic NO − 3 pollution. Tritium contents in the considered groundwaters are very heterogeneous, suggesting differences in the water turnover time or in the recharge conditions, or both. On the basis of the geographical distribution of 3H contents, a hydrogeological relation between river and the groundwater systems has been proposed for the study site. Interpretation of both 18O and 2H, as well as 3H, suggests that the recharge of the investigated groundwaters may result from three major mechanisms: (1) direct infiltration of local precipitation; (2) lateral inflow of river waters; (3) probably upward leakage of old groundwaters.

Nano-scale structure control of mesoporous silica

Structure change during a process from a layered sodium silicate, kanemite, to a noble mesoporous silica, folding sheet mesoporous materials (FSM), was studied by 29Si-MAS-NMR and X-ray powder diffraction. Cation exchange of Na + in the kanemite for hexadecyltrimethylammonium (HDTMA) ion folded unit silica sheets to form an HDTMA/silica intermediate with nano-scale hexagonal symmetry. Following pH adjustment at 8.5 promoted condensation reactions between adjacent silica sheets to form an HDTMA/silica complex, which caused local rearrangement of SiO 4-tetrahedra in the sheets. Removing the organic component from the HDTMA/silica complex by calcination at 550 °C gave a porous silica where uniform nano-scale pores were arranged regularly. XRD patterns suggested a characteristic SiO 4-tetrahedra arrangement in the walls of the porous materials.