Simultaneous leaching and carbon sequestration in constrained aqueous solutions

The behavior of metal ions’ leaching and precipitated mineral phases of metal-rich fly ash (FA) was examined in order to evaluate microbial impacts on carbon sequestration and metal immobilization. The leaching solutions consisted of aerobic deionized water (DW) and artificial eutrophic water (AEW) that was anaerobic, organic- and mineral-rich, and higher salinity as is typical of bottom water in eutrophic algae ponds. The Fe- and Ca-rich FAs were predominantly composed of quartz, mullite, portlandite, calcite, hannebachite, maghemite, and hematite. After 86 days, only Fe and Ca contents exhibited a decrease in leaching solutions while other major and trace elements showed increasing or steady trends in preference to the type of FA and leaching solution. Ca-rich FA showed strong carbon sequestration efficiency ranging up to 32.3 g CO₂/kg FA after 86 days, corresponding to almost 65% of biotic carbon sequestration potential under some conditions. Variations in the properties of FAs such as chemical compositions, mineral constituents as well as the type of leaching solution impacted CO₂ capture. Even though the relative amount of calcite increased sixfold in the AEW and the relative amount of mineral phase reached 37.3 wt% using Ca-rich FA for 86 days, chemical sequestration did not accomplish simultaneous precipitation and sequestration of several heavy metals.     

Kinetic and mechanism studies of the adsorption of lead onto waste cow bone powder (WCBP) surfaces

This study examines the adsorption isotherms, kinetics and mechanisms of Pb²⁺ sorption onto waste cow bone powder (WCBP) surfaces. The concentrations of Pb²⁺ in the study range from 10 to 90 mg/L. Although the sorption data follow the Langmuir and Freundlich isotherm, a detailed examination reveals that surface sorption or complexation and co-precipitation are the most important mechanisms, along with possibly ion exchange and solid diffusion also contributing to the overall sorption process. The co-precipitation of Pb²⁺ with the calcium hydroxyapatite (Ca-HAP) is implied by significant changes in Ca²⁺ and PO₄ ^3? concentrations during the metal sorption processes. The Pb²⁺ sorption onto the WCBP surface by metal complexation with surface functional groups such as ≡ POH. The major metal surface species are likely to be ≡ POPb⁺. The sorption isotherm results indicated that Pb²⁺ sorption onto the Langmuir and Freundlich constant q _max and K _F is 9.52 and 8.18 mg g^?1, respectively. Sorption kinetics results indicated that Pb²⁺ sorption onto WCBP was pseudo-second-order rate constants K ₂ was 1.12 g mg^?1 h^?1. The main mechanism is adsorption or surface complexation (≡POPb⁺: 61.6%), co-precipitation or ion exchange [Ca_3.93 Pb_1.07 (PO₄)₃ (OH): 21.4%] and other precipitation [Pb 50 mg L^?1 and natural pH: 17%). Sorption isotherms showed that WCBP has a much higher Pb²⁺ removal rate in an aqueous solution; the greater capability of WCBP to remove aqueous Pb²⁺ indicates its potential as another promising way to remediate Pb²⁺-contaminated media.     

Effect of inorganic carbonate and organic matter in thermal treatment of mercury-contaminated soil

Environmental Science and Pollution Research - Thermal treatment of mercury (Hg)-contaminated soil was studied to investigate the desorption behavior of Hg at different temperatures. The soil...     

Effects of adding slags on strength and leaching properties of soft soil

Journal of Material Cycles and Waste Management - Dredged soils are typically mixed with additives to improve their mechanical properties and reduce the risks of leaching toxic elements. An...     

Degradation characteristics of methyl ethyl ketone by Pseudomonas sp. KT-3 in liquid culture and biofilter

With ketone pollution forming an ever-growing problem, it is important to identify a ketone-degrading microorganism and establish its effect. Here, a methyl ethyl ketone (MEK)-degrading bacterium, Pseudomonas sp. KT-3, was isolated and its MEK degradation characteristics were examined in liquid cultures and a polyurethane-packed biofilter. In liquid cultures, strain KT-3 could degrade other ketone solvents, including diethyl ketone (DK), methyl propyl ketone (MPK), methyl isopropyl ketone (MIPK), methyl isobutyl ketone (MIBK), methyl butyl ketone (MBK) and methyl isoamyl ketone (MIAK). The maximum specific growth rate (mumax) of the isolate was 0.136 h(-1) in MEK medium supplemented with MEK as a sole carbon source, and kinetically, the maximum removal rate (Vm) and saturation constant (Km) for MEK were 12.28 mM g(-1)DCW h(-1) (DCW: dry cell weight) and 1.64 mM, respectively. MEK biodegradation by KT-3 was suppressed by the addition of MIBK or acetone, but not by toluene. In the tested biofilter, KT-3 exhibited a>90% removal efficiency for MEK inlet concentrations of around 500 ppmv at a space velocity (SV) of 150 h(-1). The elimination capacity of MEK was more influenced by SV than by the inlet concentration. Kinetic analysis showed that the maximum MEK removal rate (Vm) was 690 g m(-3) h(-1) and the saturation constant (Km) was 490 ppmv. Collectively, these results indicate the polyurethane sequencing batch biofilter with Pseudomonas sp. KT-3 will provide an excellent performance in the removal of gaseous MEK.     

Comparison of fenton and photo-fenton processes for livestock wastewater treatment

In this study, the photochemical degradation of livestock wastewater was carried out by the Fenton and Photo-Fenton processes. The effects of pH, reaction time, the molar ratio of Fe(2 +)/H(2)O(2), and the Fe(2 +) dose were studied. The optimal conditions for the Fenton and Photo-Fenton processes were found to be at a pH of 4 and 5, an Fe(2 +) dose of 0.066 M and 0.01 M, a concentration of hydrogen peroxide of 0.2 M and 0.1 M, and a molar ratio (Fe(2 +)/H(2)O(2)) of 0.33 and 0.1, respectively. The optimal reaction times in the Fenton and Photo-Fenton processes were 60 min and 80 min, respectively. Under the optimal conditions of the Fenton and Photo-Fenton processes, the chemical oxygen demand (COD), color, and fecal coliform removal efficiencies were approximately 70--79, 70--85 and 96.0--99.4%, respectively.     

Sorption and reduction of tetrachloroethylene with zero valent iron and amphiphilic molecules

Effects of surfactants and natural organic matter (NOM) on the sorption and reduction of tetrachloroethylene (PCE) with zero valent iron (ZVI) were examined in this study. PCE reduction by ZVI depended on the ionic type of the surfactants. The removal of PCE and production of TCE with non-ionic Triton X-100 and cationic hexadecyltrimethyl-ammonium (HDTMA) at one-half and two times the critical micelle concentration (CMC) were 1.2-1.8 times higher than without surfactants because of the enhanced PCE partitioning and surface concentration by the sorbed surfactants. When anionic sodium dodecyl benzene sulfonate (SDDBS) at one-half and two times CMC and NOM at 20 mg l(-1) and 50 mg l(-1) concentrations were used, the removal of PCE doubled and TCE production decreased. In the presence of SDDBS, TCE production by ZVI was lower than with HDTMA and Triton X-100 while PCE removal was higher than with the other surfactants.