clay and 2-chloroaniline

Chloro derivatives of aniline are commonly used in the production of dyes, pharmaceuticals, and agricultural agents. They are toxic compounds with a large accumulation ability and low natural biodegradability. Halloysite is known as an efficient adsorbent of toxic compounds, such as phenols or herbicides, from wastewater. Inverse LC was applied to measure the adsorption of aniline and 2-chloroaniline (2-CA), 3-chloroaniline (3-CA), and 4-chloroaniline (4-CA) on halloysite adsorbents. A peak division (PD) method was used to determine a Langmuir equation in accordance with the adsorption measurement results. The values of adsorption equilibrium constants and enthalpy were determined and compared by breakthrough curve and PD methods. The physical sense of the calculated adsorption enthalpy values was checked by applying Boudart's entropy criteria. Of note, adsorption enthalpy values for halloysite adsorbents decreased in the following order: aniline > 4-CA > 2-CA > 3-CA.

Topics: Adsorption; Aluminum Silicates; Aniline Compounds; Chromatography, Liquid; Clay

In this work microstructure, porosity and hydration degree of cement-based solidified/stabilized wasteforms were studied before assessing their leaching behaviour. 2-Chloroaniline was chosen as a model liquid organic pollutant and included into cement pastes, which were also modified with different admixtures for concrete: a superplasticizer based on acrylic-modified polymer, a synthetic rubber latex and a waterproofing agent. An organoclay, modified with an ammonium quaternary salt (benzyl-dimethyl-tallowammonium, BDMTA), was added to the pastes as pre-sorbent agent of the organic matter. All the samples were dried up to constant weight in order to stop the hydration process at different times during the first 28 days of curing, typically, after 1 day (1d), 7 days (7d) and 28 days. Then, the microstructure of the hardened cement-clay pastes was investigated by powder X-ray diffraction (XRD). The hydration degree and porosity were studied by thermal analysis (TG/DTA) and mercury intrusion porosimetry (MIP), respectively. For samples cured for 28 days a short-term leach test set by Italian regulation for industrial waste recycling (D.M. 5 February 1998) was performed. The best results showed a 5% release of the total initial amount of organic pollutant.

Topics: Adsorption; Aluminum Silicates; Aniline Compounds; Calcium Carbonate; Clay; Construction Materials; Mercury; Microscopy, Electron, Scanning; Organic Chemicals; Permeability; Polymers; Porosity; Quaternary Ammonium Compounds; Time Factors; Water; X-Ray Diffraction

The aim of the present work is to investigate the effect of a prolonged leaching test (more than a year) on the microstructure of solidified cementitious wasteforms. A set of four different cement-based monoliths (Ap, Bp, Cp and Dp) was prepared, and for each series an uncontaminated sample was prepared as reference (A-D). An organoclay was added in all pastes as pre-sorbent material for the pollutant; a model liquid organic pollutant, 2-chloroaniline (2-CA), was added only in the contaminated ones and different types of admixtures, chosen among those typically employed in the concrete mix-design, were used. After the first 28 days of curing, all the monoliths, contaminated and uncontaminated, underwent a dynamic leach testing (DLT) for more than 1 year in deionized water.

Topics: Adsorption; Aluminum Silicates; Aniline Compounds; Calcium Hydroxide; Carbonates; Clay; Construction Materials; Environmental Pollutants; Microscopy, Electron, Scanning; Minerals; Models, Chemical; Organic Chemicals; Porosity; Thermogravimetry; Water; Water Pollutants, Chemical; X-Ray Diffraction

The results of 2-chloroaniline (2-CA) immobilization experiments in cement matrices, using an organophilic clay modified with phenolic resins as pre-sorbent, are shown. The 2-CA suspended in water was kept in contact with the organoclay for 24 h, and the slurry obtained was then admixed with ordinary Portland cement (OPC) without additional water, to obtain a firm solid waste. Six cement-clay pastes were prepared with the same water-to-cement ratio (0.50 wt/wt), but with different slurry composition (water-to-organoclay ratio equal to 10 and 5 wt/wt, respectively) and different amounts of 2-CA suspended in water, namely 5000, 15 000, and 25 000 ppmw (weight). Dynamic leach tests were performed on solidified monoliths in order to assess the successful immobilization of the 2-CA. Moreover, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy analyses were carried out.

Topics: Aluminum Silicates; Aniline Compounds; Clay; Construction Materials; Environmental Pollutants; Microscopy, Electron, Scanning; Organic Chemicals; Phenols; Resins, Synthetic; Water

Immobilization of a model liquid organic pollutant, i.e. the 2-chloroaniline (2-CA), into a cement matrix using organoclays as pre-sorbent agents was investigated. Five cement-clay pastes were prepared with different nominal water-to-cement ratios (w/c=0.40, 0.25 and 0.15 wt/wt) and various amounts of waste (waste-to-cement o/c=0.20, 0.60 and 1.00 wt/wt); for comparison, a neat cement paste was also prepared. Dynamic leach tests were performed on solidified monoliths in order to assess the successful immobilization of the 2-CA. In monoliths at constant w/c ratio (0.40) the total amount of pollutant released increases with its initial content, and ranges from 15 to 35% with respect to it. By lowering w/c from 0.40 to 0.15 at constant o/c, the performances improved (<25% released). The microstructure of the hardened cement-clay pastes was characterized by quantitative X-ray diffraction (QXRD) and electronic microscopy (SEM-EDS) techniques; hydration degree was estimated by means of thermogravimetric analysis (TGA) in addition to QXRD. No evidence of any chemical reaction between 2-CA and cement phases was found. Moreover, it was shown that the most important factors affecting the cement hydration process were the total water content, i.e. the one taking also into account the water contained in the wet polluted clay, and the amount of 2-CA not firmly sorbed by the organoclay, and then freely dispersed in the paste.

Topics: Aluminum Silicates; Aniline Compounds; Clay; Construction Materials; Materials Testing; Refuse Disposal; Water Pollution