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The sorption properties of Na-modified Ukrainian Transcarpathian clinoptilolite towards neodymium aqueous solutions under dynamic conditions have been investigated. The sorption capacity of the Na-from of Transcarpathian clinoptilolite towards Nd(III) significantly depends on the concentration of neodymium salt, the pH of the solution, and the heat treatment temperature of the sorbent. Nd(III) is most efficiently sorbed from slightly alkaline solutions (pH 8.5), mainly by adsorption of neutral hydrolyzed forms of Nd(OH)3 on the surface of Na-clinoptilolite samples preheated at 75 °C. During the passage of an Nd(III) solution with a concentration of 1 µg mL-1 through the sorbent at a rate of 3 mL min-1 under optimal conditions, the sorption capacity of Na-clinoptilolite is 7.2 mg g-1, which is in 4 and 2.3 times higher than that of natural and acid-modified forms of this zeolite. It is shown that under the experimental conditions with an increase in the flow rate, the thickness of the stationary surface layer decreases, which leads to a decrease in the sorption capacity of Na-clinoptilolite. The best Nd(III) desorbents are solutions of mineral acids and acidified solutions of alkali metal salts (except NaCl), which provide 93-98 % extraction of lanthanide from the zeolite matrix. The method for neodymium trace amounts preconcentration from aqueous solutions in a solid-phase extraction mode with a further determination of this rare earth element by a spectrophotometric method was developed. The detection limit of this method is 0.75 ng mL-1 and the linearity was evaluated in the range of 2.5-500 ng mL-1.

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The authors report the potential adsorption capacities of three surfactant-modified clinoptilolites (MC)-cetylpyridinium chloride (CPC)-MC, didodecyldimethylammonium bromide (DDAB)-MC, and hexadecyltrimethylammonium bromide (HDTMA)-MC-for the removal of polycyclic aromatic hydrocarbons (PAHs) from aquatic environments and landfill leachate. A liquid-liquid extraction method was used to extract PAHs from water and GC/MS was used to analyse the PAHs. PAH accumulations on CPC-MC, DDAB-MC, and HDTMA-MC were linear over 21 successive batch adsorption tests for anthracene (708, 737, and 750 µg/g), fluoranthene (1355, 1583, and 1303 µg/g), fluorene (973, 1060, and 1147 µg/g), phenanthrene (844, 1057, and 989 µg/g), and pyrene (1343, 1569, and 1269 µg/g). The leachability after 21 successive accumulations was <2% for anthracene, <4% for fluoranthene, <3% for fluorene, <4% for pyrene, and <5% for phenanthrene for each adsorbent. PAH removals from landfill leachate for anthracene, fluoranthene, fluorene, phenanthrene, and pyrene were 97.8%, 98.6%, 95.7%, 97.0%, and 98.5% for CPC-MC and 99.0%, 99.6%, 98.0%, 99.0%, and 99.6% for DDAB-MC, respectively, meeting the fresh water quality standards established by British Columbia and the World Health Organization (WHO) for anthracene, fluoranthene, and fluorene. The molecular weight and molecular structure of PAHs and the hydrophobicity of adsorbents can fundamentally influence the PAH adsorption mechanism based on π-π stacking.

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This research paper addresses the hypothesis that an oral supplementation with organically modified clinoptilolite will improve colostrum quality in primiparous dairy cows whilst having no adverse effects on the cows' health. A total of 36 pregnant Holstein primiparous dairy cattle were randomly assigned to receive daily oral drenching, two hours following morning feeding, with 1 l of water containing either 0 g/l (n = 16) or 150 g/l (n = 20) of clinoptilolite. Treatment lasted from 24 ± 4 d prior to expected parturition until two days postpartum (pp). Colostrum was collected at 2 to 3 h, 12, 24 and 36 h pp and blood samples were collected at 24 ± 4 and 4 ± 2 d prior to parturition and 1, 2 and 7 d pp. Overall mean dry matter, fat and total protein percentage as well as IgG concentration and mass were significantly greater in colostrum collected from cattle drenched with clinoptilolite (total protein increased by 15% and IgG concentration and mass by 21 and 38% respectively at first sampling and further at second sampling). Total γ globulin and most other blood serum biochemistry parameters did not differ between cattle treated and not treated with clinoptilolite, the only exception being the fast anionic γ globulin fraction that was 17% greater at 4 ± 2 d prior to parturition and 10% lower on the 1st day pp in treated cattle. These results showed that organically modified oral clinoptilolite supplementation at 150 g/d significantly increases the IgG concentration in colostrum and has no adverse effects on the energy status, protein, lipid, and mineral metabolism in primiparous dairy cattle during prepartum period.

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Carcinogenic polycyclic aromatic hydrocarbons (PAHs) are widespread in the environment. In this study, the removal of PAHs from aqueous media was assessed using samples of clinoptilolite, a natural zeolite, pre-treated with 1 mol/L of NaCl, (Na pre-treated clinoptilolite, NC). Samples (10 g) of NC were separately modified with 5, 2, 2, and 20-mmol/L solutions of cetylpyridinium chloride (CPC), didodecyldimethyl ammonium bromide (DDAB), hexadecyltrimethylammonium bromide (HDTMA), and tetramethyl ammonium chloride (TMA) surfactants as potential cost-effective adsorbents. The kinetics, optimal sorbent dosage, and competitive effects were evaluated through batch adsorption tests using deionised water spiked with five PAHs (anthracene (50 µg/L), fluoranthene (100 µg/L), fluorene (100 µg/L), phenanthrene (100 µg/L), and pyrene (100 µg/L)). The surfactant non-modified (NC) and TMA-MC (modified clinoptilolite) exhibited PAH removal of <66% from the spiked concentration in aqueous solution, while CPC-MC, DDAB-MC, and HDTMA-MC achieved removal rates of >93% for the five PAHs after 24 h at a solid:liquid ratio of 1:100. The remaining concentrations of anthracene and fluoranthene were below 3 µg/L, and that of fluorene was <6 µg/L, lower than the water quality criteria of British Columbia, Canada, for protecting aquatic life. However, HDTMA-MC retained >83% of the fluorene. Over 80% of all PAHs were absorbed within 15 min for the CPC-MC and DDAB-MC, and the maximum adsorption was reached in <2 h. Three kinetic models were applied assuming pseudo-first-order, pseudo-second-order, and intra-particle equations, and the results were well-represented by the pseudo-second-order equation. The PAH sorption results indicated that the adsorption mechanism is based on PAH hydrophobicity, and π-π electron-donor-acceptor interaction with surfactant. CPC and DDAB with two long chain hydrocarbons had more PAH adsorption than HDTMA with one, and TMA with no long chain hydrocarbons (DDAB-MC > CPC-MC > HDTMA-MC â‰« TMA-MC > NC). With a solid:liquid ratio of 1:200, over 90%, 80%, and 70% of the anthracene, fluoranthene, and pyrene were adsorbed by the CPC-MC, DDAB-MC, and HDTMA-MC, respectively.

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Nitrogen (N) and phosphorus (P) pollution from aquaculture has increased dramatically in recent years, and it is urgent to develop a cost-effective method to clean these polluted waters. The objective of this study is to investigate N and P removal using a two-stage infiltration system based on NaCl modified clinoptilolite (NCLP) and thermally-treated calcium-rich attapulgite (TCAP). Results from a batch study indicated that the maximum ammonium sorption capacity of NCLPs was in the range of 6.64 to 7.27 mg. N/g and decreased slightly among the three particle sizes studied (0.2-0.5 mm, 0.5 mm-1.0 mm and 1-2 mm). A 150-day column experiment indicated that the two-stage infiltration system achieved an average removal efficiency of 99.4% N and 99.0% P, and a removal rate of 50.3 g N/m3/d and 8.83 g P/m3/d for an influent concentration of 50 mg N/L and 10 mg P/L with a hydraulic retention time (HRT) of 16 h. When the influent concentration increased to 100 mg N/L and 20 mg P/L, the average ammonium removal efficiency decreased to 65.3%, while the system can still keep a high average P removal efficiency of 97.9% for 72 days of the experiment. Longer HRT favored N and P removal efficiency, but short HRTs can oxygenate ammonium sorbed in the NCLP filter and thereby refresh its sorption capacity. The results also indicated that longer wet and dry cycles can enhance the N removal efficiency of the system, but had minor influence on P removal. The sorbed clays contained high N and P content and might have use as a slow-release fertilizer. The results of this study indicate that a reactive clay-based treatment system can be used for dual removal of N and P from aquaculture wastewaters, making possible the development of a sustainable aquaculture model.

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The physicochemical properties of the 24 modified clinoptilolite samples and their ammonia-nitrogen removal rates were measured to investigate the correlation between them. The modified clinoptilolites obtained by acid modification, alkali modification, salt modification, and thermal modification were used to adsorb ammonia-nitrogen. The surface area, average pore width, macropore volume, mecropore volume, micropore volume, cation exchange capacity (CEC), zeta potential, silicon-aluminum ratios, and ammonia-nitrogen removal rate of the 24 modified clinoptilolite samples were measured. Subsequently, the linear regression analysis method was used to research the correlation between the physicochemical property of the different modified clinoptilolite samples and the ammonia-nitrogen removal rate. Results showed that the CEC was the major physicochemical property affecting the ammonia-nitrogen removal performance. According to the impacts from strong to weak, the order was CEC > silicon-aluminum ratios > mesopore volume > micropore volume > surface area. On the contrary, the macropore volume, average pore width, and zeta potential had a negligible effect on the ammonia-nitrogen removal rate. The relational model of physicochemical property and ammonia-nitrogen removal rate of the modified clinoptilolite was established, which was ammonia-nitrogen removal rate = 1.415[CEC] + 173.533 [macropore volume] + 0.683 [surface area] + 4.789[Si/Al] - 201.248. The correlation coefficient of this model was 0.982, which passed the validation of regression equation and regression coefficients. The results of the significance test showed a good fit to the correlation model.

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Natural clinoptilolite tuff was mechanically converted to micro (MCP) and nano (NCP) particles. The MCP and NCP powders were respectively modified with hexadecyltrimethyl ammonium bromide (HDTMA) and dithizone (DTZ). The raw and modified samples were characterized by X-ray diffraction (XRD), Fourier transformation infra red (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and thermogravimetry (TG) and used for the removal of Pb(II) from aqueous solution. The results confirm that both ion exchange and complexation processes are responsible for removal of Pb(II) cations in the modified samples, while Pb(II) cations were only removed via an ion exchange process by the raw clinoptilolite. In this sorbent, the anionic removal property of surfactant modified zeolites (SMZs) changed to cationic removal property by an additional modification step. The best removal efficiency was observed by NCP-HDTMA-DTZ at the following experimental conditions: C(Pb(II)): 800 mg L(-1), HDTMA dosage: 0.2 mol L(-1), DTZ dosage: 5 mmol L(-1), contact time of DTZ with NCP-HDTMA: 1800 min and contact time of the sorbent with Pb(II): 360 min. The NCP-HDTMA-DTZ sorbent showed good efficiency for the removal of lead in the presence of different multivalent cations. Adsorption isotherms of Pb(II) ions obey the Langmuir equation that indicate the monolayer sorption of Pb(II). The adsorption kinetics based on the pseudo-second-order rate equation indicates that the rate limiting step involving a chemical reaction. The negative ΔH and ΔG indicate an exothermic and spontaneous process.

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