Adsorption of Phosphate and Ammonium on Waste Building Sludge.

Two selected waste building sludges (WBS) were used in this study: (i) sludge from the production and processing of prestressed concrete pillars (B) and (ii) sludge from the production of technical stone (TS). The materials were used in their original and Fe-modified forms (BFe/TSFe) for the adsorption of NH4+ and PO43- from contaminated waters. The experiments were performed on a model solution simulating real wastewater with a concentration of 1.7 mmol·L-1 (NH4+) and 0.2 mmol·L-1 (PO43-). The adsorption of PO43- had a high efficiency (>99%) on B, BFe and TSFe, while for TS, the adsorption of PO43- was futile due to the high content of available P in the raw TS. The adsorption of NH4+ on all sorbents (B/BFe, TS/TSFe) had a lower efficiency (<60%), while TS proved to be the most effective. Leaching tests were performed according to the CSN EN 12457 standard for B/BFe and TS/TSFe before and after NH4+ and PO43- sorption when the contents of these ions in the leachates were affected by adsorption experiments in the cases of B and TS. For BFe and TSFe, the ion content in the leachates before and after the adsorption experiments was similar.

Waste Brick Dust as Potential Sorbent of Lead and Cesium from Contaminated Water.

Adsorption properties of waste brick dust (WBD) were studied by the removing of PbII and CsI from an aqueous system. For adsorption experiments, 0.1 M and 0.5 M aqueous solutions of Cs+ and Pb2+ and two WBD (Libochovice-LB, and Tyn nad Vltavou-TN) in the fraction below 125 µm were used. The structural and surface properties of WBD were characterized by X-ray diffraction (XRD) in combination with solid-state nuclear magnetic resonance (NMR), supplemented by scanning electron microscopy (SEM), specific surface area (SBET), total pore volume and zero point of charge (pHZPC). LB was a more amorphous material showing a better adsorption condition than that of TN. The adsorption process indicated better results for Pb2+, due to the inner-sphere surface complexation in all Pb2+ systems, supported by the formation of insoluble Pb(OH)2 precipitation on the sorbent surface. A weak adsorption of Cs+ on WBD corresponded to the non-Langmuir adsorption run followed by the outer-sphere surface complexation. The leachability of Pb2+ from saturated WBDs varied from 0.001% to 0.3%, while in the case of Cs+, 4% to 12% of the initial amount was leached. Both LB and TN met the standards for PbII adsorption, yet completely failed for any CsI removal from water systems.

Removal of arsenate and antimonate by acid-treated Fe-rich clays.

Iron impurities in clays degrade the quality in many aspects, but available Fe oxides can significantly improve adsorption affinity of clays to anionic particles. Two natural Fe-rich clays (kaolin and bentonite) were treated in 0.5 M HCl (pH = 1.1) and 0.15 M (COOH)2 (pH = 1.2), and then used to adsorb AsV/SbV oxyanions from model solutions. After acid leaching, the equilibrium sorption capacities (qmax) increased from 2.3 × 10-3 to 39.2 × 10-3 mmol g-1 for AsV and from 2.4 × 10-3 to 40.1 × 10-3 mmol g-1 for SbV, more than doubling the adsorption yields (≈95%) of both oxyanions. Leaching in 0.5 M HCl enhanced both AsV and SbV adsorption, whereas leaching in 0.15 M (COOH)2 mainly improved the adsorption of SbV. Bentonite, which contained fewer crystalline forms of Fe, exhibited better sorption properties for both oxyanions. The leaching of Fe followed first-order kinetics, whereas the adsorption of AsV/SbV followed second-order kinetics. Acid leaching of Fe-rich clays can be used for the preparation of highly selective anionactive sorbents.

Interface Induced Growth and Transformation of Polymer-Conjugated Proto-Crystalline Phases in Aluminosilicate Hybrids: A Multiple-Quantum (23)Na-(23)Na MAS NMR Correlation Spectroscopy Study.

Nanostructured materials typically offer enhanced physicochemical properties because of their large interfacial area. In this contribution, we present a comprehensive structural characterization of aluminosilicate hybrids with polymer-conjugated nanosized zeolites specifically grown at the organic-inorganic interface. The inorganic amorphous Al-O-Si framework is formed by alkali-activated low-temperature transformation of metakaoline, whereas simultaneous copolymerization of organic comonomers creates a secondary epoxide network covalently bound to the aluminosilicate matrix. This secondary epoxide phase not only enhances the mechanical integrity of the resulting hybrids but also introduces additional binding sites accessible for compensating negative charge on the aluminosilicate framework. This way, the polymer network initiates growth and subsequent transformation of protocrystalline short-range ordered zeolite domains that are located at the organic-inorganic interface. By applying an experimental approach based on 2D (23)Na-(23)Na double-quantum (DQ) MAS NMR spectroscopy, we discovered multiple sodium binding sites in these protocrystalline domains, in which immobilized Na(+) ions form pairs or small clusters. It is further demonstrated that these sites, the local geometry of which allows for the pairing of sodium ions, are preferentially occupied by Pb(2+) ions during the ion exchange. The proposed synthesis protocol thus allows for the preparation of a novel type of geopolymer hybrids with polymer-conjugated zeolite phases suitable for capturing and storage of metal cations. The demonstrated (23)Na-(23)Na DQ MAS NMR combined with DFT calculations represents a suitable approach for understanding the role of Na(+) ions in aluminositicate solids and related inorganic-organic hybrids, particularly their specific arrangement and clustering at interfacial areas.

Modified aluminosilicates as low-cost sorbents of As(III) from anoxic groundwater.

The utilization of low-grade clay materials as selective sorbents represents one of the most effective possibilities of As removal from contaminated water reservoirs. The simple pre-treatment of these materials with Fe (Al, Mn) salts can significantly improve their sorption affinity to As oxyanions. The natural kaolin calcined at 550 degrees C (mostly metakaolin) and raw bentonite (mostly montmorillonite) pre-treated with Fe(II), Fe(III), Al(III) and Mn(II) salts were used to remove of As from the model anoxic groundwater with As(III) concentration about 0.5 and 10 mg L(-1). All the pre-treating methods were appropriate for bentonite; the efficiency of As(III) sorption varied from 92 to >99%, by the sorption capacity higher than 4.5 mg g(-1). In the case of metakaolin, Fe(II)- and Mn(II)-treatments proved the high sorption efficiency (>97%), while only <50% of As was removed after Fe(III) and Al(III) pre-treatment. The sorption capacities of treated metakaolin ranged from 0.1 to 2.0 mg g(-1).

Sorption of As(V) on aluminosilicates treated with Fe(II) nanoparticles.

Adsorption of arsenic on clay surfaces is important for the natural and simulated removal of arsenic species from aqueous environments. In this investigation, three samples of clay minerals (natural metakaoline, natural clinoptilolite-rich tuff, and synthetic zeolite) in both untreated and Fe-treated forms were used for the sorption of arsenate from model aqueous solution. The treatment of minerals consisted of exposing them to concentrated solution of Fe(II). Within this process the mineral surface has been laden with Fe(III) oxi(hydroxides) whose high affinity for the As(V) adsorption is well known. In all investigated systems the sorption capacity of Fe(II)-treated sorbents increased significantly in comparison to the untreated material (from about 0.5 to >20.0 mg/g, which represented more than 95% of the total As removal). The changes of Fe-bearing particles in the course of treating process and subsequent As sorption were investigated by the diffuse reflectance spectroscopy and the voltammetry of microparticles. IR spectra of treated and As(V)-saturated solids showed characteristic bands caused by Fe(III)SO(4), Fe(III)O, and AsO vibrations. In untreated As(V)-saturated solids no significant AsO vibrations were observed due to the negligible content of sorbed arsenate.