Removal of harmful components from MSWI fly ash as a pretreatment approach to enhance waste recycling.

Mineral carbonation using alkaline waste and byproducts to reduce CO_2 emissions in Taiwan

Abstract This study was conducted to evaluate the phosphate sorption properties of eggshell (ES) and calcined ESs (C-ESs) in a high-concentration phosphate solution. The C-ESs yield decreased rapidly at 900 °C, indicating that the CaCO 3 constituting the ES was converted to CaO by the high calcination temperature. The optimum calcination temperature for phosphate removal using C-ES was 900 °C. The actual sorption amount of phosphate by ES and C-ES900 was in agreement with the Langmuir isothermal sorption equation, and the maximum sorption capacities derived from this equation were 178.6 and 270.3 mg/g, respectively. The sorption rate of phosphate by ES and C-ES900 was divided into two stages: an initial fast sorption stage, followed by a slow sorption stage. The sorption of phosphate by ES was dominantly influenced by the initial pH and salt concentration, whereas C-ES900 exhibited a constant sorption capacity regardless of environmental changes. The SEM–EDS and XRD results demonstrated that phosphate was successfully adsorbed on the ES and C-SE900 surfaces. In this study, it was found that the sorption of phosphate by ES occurred via ion exchange and precipitation reactions and that the sorption of phosphate by C-ES900 was dominantly affected by precipitation. Above all, C-ES can be applied as an effective adsorbent for removing high concentrations of phosphate under a wide range of environmental conditions. 

/pdf/removal-of-phosphates-using-eggshells-and-calcined-eggshells-589ryam6.pdf

Removal of phosphates using eggshells and calcined eggshells in high phosphate solutions

High-sulfur coal gangue (HS-CG) is extremely unstable in the environment, releasing acid mine drainage with high concentrations of harmful heavy metals (HMs). The effects of HS-CG particle size, leaching solution pH, Fe3+ and acidophilic microorganisms on the release of HMs from the HS-CG and their kinetic behavior were studied using static leaching tests. The results showed that the smaller the particle size of HS-CG and the more acidic the leaching solution, the greater the release of HMs. As the chemical catalyst, the external addition of 300 mg/L Fe3+ can make the leaching amount of Fe, Mn, Cu, Zn, Ni, Cr reached 10,224.93, 93.88, 52.25, 11.56, 7.55, 2.97 mg/kg respectively, and the release of HMs was 1.36–2.60 times of the tests without the addition of iron. However, the concentration of Fe3+ above 800 mg/L promoted the production of jarosite on the surface of HS-CG, which led to decrease in the release of HMs. The HMs forms in HS-CG were different, while the effect of microorganisms on the leaching of Zn (54.99%) and Mn (52.35%) in the higher acid soluble fraction was more obvious, their leaching amount reached 87.21 and 107.58 mg/kg respectively. The kinetic analysis indicated that the rate-controlling step was mainly redox reaction at first, and then gradually controlled by the diffusion of ash layer. So, the kinetic equation controlled jointly by two rate-controlling stages has been proposed to describe the dissolution of HS-CG. This work help develop pertinent strategies for mine area remediation via controlling the HMs generation path. 

Release characteristics of heavy metals in high-sulfur coal gangue: Influencing factors and kinetic behavior.

Novel hydroxyapatite (HAP)-assisted hydrothermal solidification of heavy metals in fly ash from MSW incineration: Effect of HAP liquid-precursor and HAP seed crystal derived from eggshell waste

Stability evaluation of potentially toxic elements in MSWI fly ash during carbonation in view of two leaching scenarios

Stability evaluation of potentially toxic elements in MSWI fly ash during carbonation in view of two leaching scenarios.

Toxicity Characteristic Leaching Procedure (TCLP, USA) and Acetic Acid Buffer Solution Method (HJ/T 300–2007, China) are often used to simulate the leaching process of heavy metals from MSW incineration fly ash after entering sanitary landfill under the influence of landfill leachate. However, the results based on the standards can neither obtain the actual leaching pattern of heavy metals, nor evaluate or predict their environmental risk evolution. In this study, the leachate characteristics and leachability of Cd, Cu, Pb, Zn, Cr, and Ni during the co-landfilling of chelating agents or phosphate stabilized fly ash and MSW were investigated using three simulated landfill columns under rainfall conditions. The maximum leaching concentration of Pb and Cd in the co-landfill of chelate stabilized fly ash and MSW exceeded the corresponding standard limits, and that of Pb, Cd, and Ni for the scenario of co-landfill of phosphate stabilized fly ash and MSW exceeded the corresponding standard limits. In general, there were higher leaching concentrations of heavy metals in the initial stage (Pb, Cd, Zn, and Cr) and middle stages (Cu and Ni) of the landfill. Compared with those of the landfill with MSW alone, the pH, volatile fatty acids (VFA) and ammonia (NH4+-N) concentration were high in the leachate from the co-landfill with stabilized fly ash and MSW. The pH and chemical oxygen demand (COD) of the leachate might be the primary factors affecting the leaching behavior of heavy metals, whereas VFA and NH4+-N seemed to have little effect. This study demonstrated that evaluating the leaching risk of heavy metals according to actual disposal scenarios, is a more effective method than the standard methods. 

Thomas Doherty

Papers

Stability evaluation of potentially toxic elements in MSWI fly ash during carbonation in view of two leaching scenarios

Stability evaluation of potentially toxic elements in MSWI fly ash during carbonation in view of two leaching scenarios.

Stabilized MSW incineration fly ash co-landfilled with organic waste: Leaching pattern of heavy metals and related influencing factors