Recovery of soluble chlorides from municipal solid waste incineration fly ash using evaporative crystallisation and flotation methods

Surface chemistry features in the flotation of KCl

At present, domestic waste incineration fly ash is classified as hazardous waste. The technical hurdle of fly ash detoxification and resource usage must be overcome in order to effectively utilize fly ash resources. In this study, we investigate the migration and transformation of heavy metal contaminants in the course of utilizing domestic waste incineration fly ash resources through the technology pathway of low-temperature pyrolysis, cyclic rinsing, and evaporation crystallization. Firstly, a comparative analysis was conducted on the fly ash (FA), pyrolysis ash (PA), and water-washing ash (WA) resulting from domestic waste incineration, revealing 24 types of metals, 3 types of non-metals, and 8 types of oxides. We observed the variations in heavy metal concentrations as well as the acidity and alkalinity in three types of ash resulting from the regenerated salt (RS) and incineration processes. Moreover, we analyzed the changes in heavy metal levels and acidity and alkalinity of treated saline water (TSW) and industrial brine (IB), which originate from the fly ash treatment process. The study’s results have confirmed that the heavy metal content in RS was below the detection limit following resource treatment. In addition, the regenerated salt product is determined to be a CaO-SiO2-Al2O3-Fe2O3 system, which enables the utilization of fly ash as a valuable resource. Notably, there were significant changes observed in heavy metal content in TSW and IB. Continued attention needs to be paid to the potential risk of environmental contamination from heavy metals and dioxins in FA infiltration. This research will prove beneficial in assessing resource utilization potential of products subjected to environmentally sound incineration fly ash treatment.

The stability of coal/n-alkane film—air bubble—water systems and froth flotation of coal

Relationship between breakthrough pressure and contact angle for organo-silane treated coal fly ash

The separation of sylvite (KCl) and halite (NaCl), two main minerals in potash ores, is difficult because of the high ion concentration, fine particles of NaCl, and aggregation of KCl and NaCl in the saturated system. This study employed ammonium chloride (NH4Cl) as a new depressant and dodecyl morpholine as a collector in the reverse flotation process. The depressing mechanisms were studied by adsorption capacity experiments, infrared spectral analysis, and molecular dynamics simulations. The flotation tests showed that NaCl recovery increased to 97% after the addition of NH4Cl, while KCl recovery was reduced to <1%. Notably, NH4Cl not only acted as a selective KCl depressant, but also activated NaCl flotation. The FTIR measurements showed that NH4Cl was physically adsorbed onto the KCl and NaCl surfaces. Adsorption capacity experiments and molecular dynamics simulations confirmed more favorable NH4Cl adsorption on the KCl surface than on the NaCl surface. Moreover, the KCl mineral surface was more hydrophilic, while that of NaCl was more hydrophobic. Relative concentration analysis revealed that >90% ammonium and chloride ions were distributed 2–10 Å away from the KCl surface but were dispersed on the NaCl surface, indicating that NH4Cl exhibited stronger intermolecular interactions with KCl than with NaCl.

Flotation has become a significant technique for the KCl separation from NaCl-containing complex systems, but the true nature of adsorption selectivity of collector on the crystal surface of KCl is still unclear. In this study, using density functional theory calculations, we investigated the adsorption behaviors of a commonly used collector, octadecylamine hydrochloride (ODA), on the crystal surfaces of KCl and NaCl, respectively. The results demonstrate that the structure of built crystals for calculation is validity and the crystal surfaces containing two-layer atoms are most stable. All adsorption energies of ODA+ cation and H2O molecule on the crystal surfaces of KCl and NaCl are negative with the decreased absolute value according to the sequence of KCl-ODA+ >NaCl-H2O > KCl-H2O > NaCl-ODA+, suggesting that the interaction between ODA and KCl is stronger than that in the other considered systems. The differences of interaction energies demonstrate the adsorption selectivity of ODA on KCl, resulting in the selectively flotation. Therefore, we construct accurate models to simulate the actual crystal surface structures of KCl and NaCl, and we provide adsorption energies as complementary evidences to interpret the floatability of KCl from the NaCl mixture, which can help to design new collectors for the flotation of soluble salts.

A mixed separation-immobilization method for soluble salts removal and stabilization of heavy metals in municipal solid waste incineration fly ash

Improved water and efflorescence resistance of flue gas desulfurization gypsum-based composites by generating hydrophobic coatings

Carbon removal flotation performance and economic analysis of different coal fly ash using waste fried oil as a collector

Lead-zinc sulphide ore mined from the Toranica deposit and is processed in the concentrator. Thedeposit is located in the Osogovo mountain, the northeastern part of the Republic of North Macedonia, near theBulgarian Macedonian border. The main ore minerals in the lead-zinc ore are represented by galena, sphalerite,chalcopyrite, pyrite, and the non-ore minerals by quartz, carbonates, barite. After crushing and grinding, the oreis beneficiated using a direct selective flotation. It is common knowledge that slurry agitation is important forthe flotation efficiency and makes the mineral particles fully mix with the flotation reagent. It was establishedthat with the available conditioning tank agitator in the Toranica lead-zinc concentrator, the necessary slurryagitation is not achieved. This leads to inefficient flotation process and low-quality Pb and Zn concentratesproduction. During certain periods of the concentrator's operation, a zinc concentrate with an average monthlycontent of lead impurities is produced, reaching up to 6.08%, while at the same time a lead loss was registeredin the final flotation tails. To eliminate the causes leading to deteriorate technological indicators, the lead-zincore mineral composition was investigated. Moreover, slurry agitation has been improved by implementing anadvanced conditioning tank. High-quality final concentrates production was achieved, and the recovery degreewas also increased. This paper is organized divided into four sections. Section 1 gives a brief overview ofsulphide lead-zinc ores, their flotation beneficiation, reagents and flowsheets. The second section examines ourresearch and development program to establish the technological possibilities for replacement of an availableconditioning tank agitator. In the third section the case study is analyzed, and we propose a new procedure forconditioning tank agitator improvement. Our conclusions are drawn in the final section

1.25 per cent gelatin solutions containing enough NaOH to bring them to pH 7.367 (or KOH to pH 7.203) were made up with various concentrations of NaCl, KCl and MgCl(2), alone and in mixtures, up to molar ionic strength. The effects of these salts on the pH were observed. MgCl(2) and NaCl alone lower the pH of the Na gelatinate or the K gelatinate, in all amounts of these salts. KCl first lowers the pH (up to 0.01 M K(+)), then raises the pH. Mixtures of NaCl and KCl (up to 0.09 M of the salt whose concentration is varied) raise the pH; then (up to 0.125 M Na(+) or K(+)) lower the pH; and finally (above 0.125 M) behave like KCl alone. Mixtures of MgCl(2) and NaCl raise the pH up to 0.10 M Na(+), and lower it up to 0.15 M Na(+)regardless of the amount of MgCl(2). Higher concentrations of NaCl have little effect, but the pH in this range of NaCl concentration is lowered with increase of MgCl(2). Mixtures of MgCl(2) and KCl behave as above described (for MgCl(2) and NaCl) and the addition of NaCl plus KCl to gelatin containing MgCl(2) produces essentially the same effect as the addition of either alone, except that the first two breaks in this curve come at 0.07 M and 0.08 M [Na(+) + K(+)] and there is a third break at 0.12 M. In this pH range the free groups of the dicarboxylic acids and of lysine are essentially all ionized and the prearginine and histidine groups are essentially all non-ionized. The arginine group is about 84 per cent ionized. Hence we are studying a solution with two ionic species in equilibrium, one with the arginine group ionized, and one with it non-ionized. It is shown that the effect of each salt alone depends upon the effect of the cation on the activity of these two species due to combination. The anomalous effects of cation mixtures may be qualitatively accounted for if one or both of these species fail to combine with the cations in a mixture in proportion to the relative combination in solutions of each cation alone. Special precautions were taken to ensure accuracy in the pH measurements. The mother solutions gave identical readings to 0.001 pH and the readings with salts were discarded when not reproducible to 0.003 pH. All doubtful data were discarded.

Comprehensive understanding the transition behaviors and mechanisms of chlorine and metal ions in municipal solid waste incineration fly ash during thermal treatment

This paper investigates the influence of using environmental by-product materials such as Silpozz and Fly Ash (FA) in concrete properties to resist saline water. The mix design is targeted for M30 grade concrete. Five concrete mixtures were designed to have the same degree of workability with water to cementitious material ratio of 0.43. The plain cement concrete samples made 0% replacement of FA and Silpozz with cement. The blended cement concrete samples made with 10% replacement of FA and 10%, 20%, 30%, and 40% replacement of silpozz with cement. Two set of samples (cube, cylinder and prism) have been prepared. One set of sample, after 28 days of Normal Water Curing (NWC) was being immersed in sea water for 7, 28 and 90 days and the other set of samples have been cured in normal water for 7, 28 and 90 days. The studied parameters include the compressive strength, flexural strength and split tensile strength of NWC and Sea Water Curing (SWC) samples after 28 days of NWC for 7, 28, and 90 days curing period. The acid soluble chloride and water soluble chloride contents were measured through the concrete samples of 28 days SWC after 28 days of NWC. The obtained test results indicated that the use of FA and Silpozz in concrete showed significant resistance to chloride penetration up to 10% replacement of FA and 30% replacement of Silpozz with cement. The carbonation depth of concrete samples for 90 days SWC after 28 days of NWC was measured. There is no significant change in depth of carbonation. The percentage increase in compressive strength for blended cement concrete in NWC is better than the samples in SWC after 28 days of NWC.

Organosilane (OS) treatment for water repellency has gained attention as a mechanism for mitigating leaching and for possible beneficial reuse of coal combustion residuals, particularly coal fly ash (CFA). However, little effort has been devoted to understanding the interaction between OS-treated CFA and water under conditions representative of field applications. In this study, the construction conditions of OS-treated CFA were simulated in the laboratory, and the degree of induced water repellency was investigated through contact angle measurements. A class F CFA from a coal-fired electric power plant ash impoundment and a commercially available OS were used. Besides CFA geotechnical and geochemical characterisation, samples were prepared by post-compaction treatment of CFA with OS solutions applied by spraying, which simulates a field irrigation truck. Results indicate that a 7% volume concentration of the OS solution is appropriate for construction purposes. However, the degree of water repellency, as measured by using contact angles, is strongly dependent on the water content of the compacted CFA. This suggests that the contractor should compact the CFA first, then apply truck-mounted jet drying or a similar technique and finally spray the OS solution on the surface. Results also demonstrate that about 84% of the treatment accumulates in the upper 5 cm of the compacted CFA.

This work aims to evaluate the performance of graphene nanoplatelet (GNP) as conductive filler with the presence of 0.5 wt.% cellulose nanofiber (CNF) on the physical, mechanical, conductivity and thermal properties of jatropha oil based waterborne polyurethane. Polyurethane was made from crude jatropha oil using an epoxidation and ring-opening process. 0.5, 1.0, 1.5, 2.0 wt.% GNP and 0.5 wt.% CNF were incorporated using casting method to enhance film performance. Mechanical properties were studied following standard method as stated in ASTM D638-03 Type V. Thermal stability of the nanocomposite system was studied using thermal gravimetric analysis (TGA). Filler interaction and chemical crosslinking was monitored using Fourier-transform infrared spectroscopy (FTIR) and film morphology were observed with field emission scanning electron microscopy (FESEM). Water uptake analysis, water contact angle and conductivity tests are also carried out. The results showed that when the GNP was incorporated at fixed CNF content, it was found to enhance the nanocomposite film, its mechanical, thermal and water behavior properties as supported by morphology and water uptake. Nanocomposite film with 0.5 wt.% GNP shows the highest improvement in term of tensile strength, Young’s modulus, thermal degradation and water behavior. As the GNP loading increases, water uptake of the nanocomposite film was found relatively small (<1%). Contact angle test also indicates that the film is hydrophobic with addition of GNP. The conductivity properties of the nanocomposite film were not enhanced due to electrostatic repulsion force between GNP sheet and hard segment of WBPU. Overall, with addition of GNP, mechanical and thermal properties was greatly enhanced. However, conductivity value was not enhanced as expected due to electrostatic repulsion force. Therefore, ternary nanocomposite system is a suitable candidate for coating application.