Christian J. Engelsen

Speciation analysis of As, Sb and Se in leachates of cementitious construction materials using selective solid phase extraction and ICP-MS

A solid phase extraction (SPE) method has been developed for the separation of As(III), Sb(III) and Se(IV) from As(V), Sb(V) and Se(VI) in leachates of cementitious construction materials. The leachates were treated with ammonium pyrrolidine dithiocarbamate (APDC) and the APDC complexes of As(III), Sb(III) and Se(IV) were retained on a non-polar (C-18) sorbent, whereas As(V), Sb(V) and Se(VI) passed through. The SPE method was optimized in a multivariate approach: the effect of sample pH, APDC concentration, mixing time and sample percolation rate on the extraction of the analyte species was studied, and the optimum conditions of the significant parameters, i.e. sample pH and APDC concentration, were identified and experimentally verified. The two oxidation states of the elements can be separated using the SPE method from solutions of pH 3–8 (As), pH 4–10 (Sb) and pH 3–9 (Se) treated with 0.08% (w/v) APDC. The effect of matrix interferences was studied and the use of benzene sulfonate to remove interfering matrix metal ions by ion-pair SPE was demonstrated. The limit of detection of As(V), Sb(V) and Se(VI) by ICP-MS was 0.09, 0.14 and 0.37 µg L−1, respectively. A condition was established for the preconcentration of As(III), Sb(III) and Se(IV) by elution with 3.0 M HNO3 in a back-flushing mode. With a preconcentration factor of 50, concentrations of As(III), Sb(III) and Se(IV) down to 1–6 ng L−1 could be detected using the SPE method in combination with ICP-MS. The SPE method was validated using spike recovery tests, and was used to determine the oxidation states of the target elements in leachates of a concrete material. As(V), Sb(V) and Se(VI) were found to be the major species in most of the leachates.

Field site leaching from recycled concrete aggregates applied as sub-base material in road construction

The release of major and trace elements from recycled concrete aggregates used in an asphalt covered road sub-base has been monitored for more than 4 years. A similar test field without an asphalt cover, directly exposed to air and rain, and an asphalt covered reference field with natural aggregates in the sub-base were also included in the study. It was found that the pH of the infiltration water from the road sub-base with asphalt covered concrete aggregates decreased from 12.6 to below pH 10 after 2.5 years of exposure, whereas this pH was reached within only one year for the uncovered field. Vertical temperature profiles established for the sub-base, could explain the measured infiltration during parts of the winter season. When the release of major and trace elements as function of field pH was compared with pH dependent release data measured in the laboratory, some similar pH trends were found. The field concentrations of Cd, Ni, Pb and Zn were found to be low throughout the monitoring period. During two of the winter seasons, a concentration increase of Cr and Mo was observed, possibly due to the use of de-icing salt. The concentrations of the trace constituents did not exceed Norwegian acceptance criteria for ground water and surface water Class II.

Optimization of an anion-exchange high performance liquid chromatography-inductively coupled plasma-mass spectrometric method for the speciation analysis of oxyanion-forming metals and metalloids in leachates from cement-based materials

A method was developed for the speciation analysis of the oxyanions of As(III), As(V), Cr(VI), Mo(VI), Sb(III), Sb(V), Se(IV), Se(VI) and V(V) in leachates from cement-based materials, based on anion-exchange HPLC coupled with ICP-MS. The method was optimized in a two-step multivariate approach: the effect of sample pH and mobile phase composition on resolution, peak symmetry and analysis time was studied. Optimum conditions were then identified for the significant experimental factors by studying their interdependence. A mobile phase composition of 20 mM ammonium nitrate, 50 mM ammonium tartrate and pH 9.5 was found to be a compromise optimum for the separation of the target analytes using isocratic elution. The optimum condition provided separation of the analytes in less than 6 min, at a mobile phase flow rate of 1.0 mL/min. The signal intensities of the analytes were improved by adding 1% methanol to the mobile phase. The limit of detection of the method was in the range 0.2-2.2 μg/L for the various species. The effect of sample constituents was studied using spiked concrete leachates. The method was used to determine the target oxyanionic species in leachates generated from a concrete material in the pH range 3.5-12.4; CrO(4)(2-), MoO(4)(2-) and VO(4)(3-) were detected in most of the leachates.

Fractionation analysis of oxyanion-forming metals and metalloids in leachates of cement-based materials using ion exchange solid phase extraction

A simple and versatile solid phase extraction (SPE) method has been developed to determine the anionic species of As, Cr, Mo, Sb, Se and V in leachates of cement mortar and concrete materials in the pH range 3-13. The anionic fractions of these elements were extracted using a strong anion exchanger (SAX) and their concentrations were determined as the difference in element concentration between the sample and the SAX effluent. Inductively coupled plasma mass spectrometry (ICP-MS) was used off-line to analyse solutions before and after passing through the SAX. The extraction method has been developed by optimizing sorbent type, sorbent conditioning and sample percolation rate. Breakthrough volumes and effect of matrix constituents were also studied. It was found that a polymer-based SAX conditioned with a buffer close to the sample pH or in some cases deionised water gave the best retention of the analytes. Optimal conditions were also determined for the quantitative elution of analytes retained on the SAX. Extraction of the cement mortar and concrete leachates showed that most of the elements had similar distribution of anions in both leachate types, and that the distribution was strongly pH dependent. Cr, Mo and V exist in anionic forms in strongly basic leachates (pH>12), and significant fractions of anionic Se were also detected in these solutions. Cr, Mo, Se and V were not determined as anions by the present method in the leachates of pH<12. Anionic As and Sb were found in small fractions in most of the leachates.

Overcoming matrix interferences in ion-exchange solid phase extraction of As, Cr, Mo, Sb, Se and V species from leachates of cement-based materials using multiple extractions

Solid phase extraction (SPE) methods based on multiple extractions have been developed to overcome matrix interferences in the charge-based fractionation analysis of As, Cr, Mo, Sb, Se and V leached from cement-based materials. Disposable SPE tubes packed with 500 mg strong anion-exchange (SAX) or strong cation-exchange (SCX) sorbents were used to extract the anionic and cationic species of the elements, respectively. The multiple extractions were based on the percolation of a small sample volume (5.0 mL) through a series of identical ion-exchange tubes. For most of the elements, more than 90% of the anionic species were extracted from a sample containing up to 16 g L(-1) NO(3)(-) by passing the aliquot through five identical SAX tubes. Percolating a sample aliquot through three identical SCX cartridges gave more than 99% retention for Cr(III) from leachates containing a high concentration of interfering metal cations. The anionic and cationic analytes showed only slight non-specific adsorption on the SCX and SAX sorbents, respectively, except for V(V) on the SCX sorbent. A condition was established for the quantitative elution of the retained analytes from the ion-exchange sorbents with 1.0 mol L(-1) HNO(3). The multiple ion-exchange SPE procedures were validated using spike recovery tests. The methods were used to determine the anionic and cationic fractions of the target elements in concrete leachates covering a broad range of pH (3.8-13.4). The elements were found to exist predominantly as anions in the alkaline and neutral leachates. A high fraction (85%) of cationic Cr was detected in the most acidic leachate (pH 3.8).

A comprehensive physico-chemical, mineralogical and morphological characterization of Indian mineral wastes

This paper provides a comprehensive characterization of mineral waste such as fly ash, bottom ash, slag and construction demolition (C&D) collected from four different thermal power plants, three steel plants and three C&D waste generation sites in India. To determine utilisation potential and environmental concerns, as received fly ash, bottom ash, slag and C&D waste were analysed for physico-chemical, mineralogical and morphological properties. The physico-chemical properties analysed include pH, moisture content, acid insoluble residue, loss on ignition(LOI), carbon content, fineness, chloride content, sulphate content, reactive silica content, XRF and heavy metal analysis. Morphological and mineralogical characteristics were investigated using scanning electron microscopy–energy dispersive X-ray. Particle size distribution was obtained using particle size analyser. The material analysed has different compositions and were selected with a view to determine their suitability for different applications in cement and concrete industry and for further research studies.

Distribution of Hg, As and Se in material and flue gas streams from preheater–precalciner cement kilns and vertical shaft cement kilns in China

The aim of this study was to evaluate the behavior of Hg, As, and Se in cement production. Two types of cement plants were studied, including the vertical shaft kiln (VSK) and preheater–precalciner kiln (PPK) processes. Determination of Hg, As, and Se in the main material and gas streams were performed. It was found that recycling of particulate matter captured by an air pollution control device caused a significant enrichment of Hg and As inside both processes. The total quantity of Hg entering the process and the quantity emitted to the atmosphere were found to be 10–109 and 6.3–38 mg, respectively, per ton of clinker produced. The average Hg emission was calculated to be around 41% of the total mercury input. The emissions found complied with the European Union (EU) limit and exceeded partly the U.S. limit. Furthermore, it was found that oxidized mercury was the dominant species in the PPK process, whereas the reduced form was dominant in the VSK process, due to the oxidizing and reducing gas conditions, respectively. Regarding the distribution of As and Se, the major amounts were bound to the solid materials, that is, cement clinker and particulate matter. Based on cement production data in China in 2013, the annual emissions of Hg and As were estimated to be in the range of 8.6–52 and 4.1–9.5 tons, respectively. Implications: There are fairly limited studies on Hg, As, and Se measurements from cement manufacturing facilities in China, and even more limited studies on the behavior in vertical shaft kilns. The needs for increased emission reduction efforts in energy-intensive industries are globally recognized, and an improved understanding of the processes ongoing in a cement kilns system is decisive. Since the processes are complex and almost impossible to recreate in the laboratory, field measurements are indeed important. The findings in the present study were solely based on field measurements and the data are considered to be valuable for the further development of emission reduction technology.

Recycling of rock materials as part of sustainable aggregate production in Norway and Italy

Resource preservation and increased waste recycling are important for sustainability in Europe. Thus, it is essential to achieve environmentally safe and sound management of quarry waste (QW) at European and national level. Rock materials recycling practice has therefore been studied in Norway and Italy. At present, recycling levels vary and systematic recovery is not common in European countries. Furthermore, QW is often landfilled owing to unclear legislation and a general lack of technical data. It was found that 80 – 90% and 30 – 80% of the quarrying volumes end up as QW in Norway and Italy, respectively. Furthermore, the fine fraction constitutes around 40% of the total production of dimension stone and natural aggregate in Norway. However, continuing project initiatives over the past 5 – 10 years have shown that QW can be used to produce aggregate. In addition, positive economic and environmental effects are likely to be achieved by systematic recycling of QW planned by industries and public authorities. However, no significant incentives for recycling or systematic approaches for local aggregate exploitation exist in Italy and Norway. These need to be developed and implemented to change current practice in a major way.

CCR characterization and valorization as mineral additives during cement production in India

ABSTRACT The study emphasizes on physico-chemical, mineralogical, morphological, and mechanical characteristics of Coal Combustion Residues (CCRs) collected from two different thermal power plants. To determine utilization potential and valorization, specifically in the Indian cement sector more than governing guidelines of Indian Standards (IS), collected CCRs (Fly and Bottom Ash) samples were analyzed for physical, chemical, and mechanical characteristics. The characterization included pH, moisture content, acid insoluble residue, chlorides, reactive silica, LOI, carbon, Blaine fineness, XRF, SEM, XRD, FTIR, initial and final setting time, consistency and soundness, lime reactivity, and compressive strength at 7, 28, and 90 days. The characteristics were analyzed and selected with a view to determine their suitability as mineral additives in the cement sector. The study showed that; collected CCR samples fulfill the requirements of the Indian standard (IS:3812) as well as ASTM C-618 for physico-chemical and mechanical characteristics and show potential for increased use in the cement industry as mineral additives. The study also highlights that; up to 30% CCRs can be used as a mineral additives during cement manufacturing, and if long-term strength is considered up to 50% replacement can be possible.

An Assessment of C&D Waste Quality and Its Recycling Potential—An Indian Perspective

The present research work evaluates physico-chemical, mineralogical and mechanical characterizations of Construction–Demolition (C&D) waste so that basic and relevant information about nature of C&D waste can be determined. The comprehensive characterization of C&D waste collected from two waste generation sites in India were carried out. The material analysed has different compositions and was selected with a view to determine their suitability for concrete industry as Recycled Aggregates (RA) and for further research studies. It was observed that different physico-chemical, mineralogical and mechanical characteristics of C&D wastes were variable parameters. The basic mechanical properties of RA were within the limit of Indian Standard IS:383 and IS:6579. During compressive strengths test of C&D for M-20 grade cubes as per IS:516, it was observed that the target cube strength was achieved at 7 and 28 days and was higher for 90 days. The study shows the potential of C&D waste as RA and can be reliable alternatives to Natural Aggregates (NA) during concrete making.