China
Africa
Explore chapters and articles related to this topic
Speciation of Heavy Metals: an Approach for Remediation of Contaminated Soils
Published in Donald L. Wise, Debra J. Trantolo, Edward J. Cichon, Hilary I. Inyang, Ulrich Stottmeister, Remediation Engineering of Contaminated Soils, 2000
Two different thermodynamic approaches can be used to calculate metal-ion speciation, either by using equilibrium constants or by using Gibbs free-energy values, which are subject to conditions of equilibrium and mass balance. Even though the same thermodynamic calculations can be applied to both inorganic and organic metal complexes, the structure and binding mechanism of the organic ligands is not clearly understood at the present time and hence we do not have reliable thermodynamic data for realistic organic species.
Performance of acid mine drainage sludge as an innovative catalytic oxidation source for treating vehicle-washing wastewater
Published in Journal of Dispersion Science and Technology, 2021
The interaction between the pH (Γ2) and AMD (Γ3) is represented in Figures 4D and 5D, which shows the ideal removal efficiency that is at the acidic pH medium and the optimum AMD dose. However, the AMD dose rather than the optimum influences the COD and TOC oxidation rate and, therefore, reduces the process performance. The excess AMD results in more iron species in the system that traps the ˙OH radicals. Hence, the overdosing of the AMD to the system inhibits the overall reaction rate. Moreover, the change in pH plays a vital role on the iron ion speciation in the solution that also affects ˙OH radical production. This signifies that both AMD speciation and hydrogen peroxide decomposition are influenced with the pH range.[48]
The electric conductance of dilute sulfuric acid in water: a new theoretical interpretation
Published in Molecular Physics, 2021
The conductance data of sulfuric acid in pure methanol fit a 1–1/1–2 mixed electrolyte behaviour, thus negating a 1–3 behaviour. This further strengthens the view that the analysis in the present study and preceding papers [1–4], according to which aqueous sulfuric acid is a strong 1–3 electrolyte hence a fully dissociated triprotic H3A acid, is not coincidental and/or the product of theory’s flaws. The proposed H4SO5 structure (para-sulfuric acid) in water obviously cannot be generated by dissolving H2SO4 in pure methanol. Also, H4SO5 is not expected to be stable in methanol: First, methanol has much lower permittivity (ε, ∼30–35 at 25 ± 5°C) compared to water (78.4 at 25°C) and weaker hydrogen bonding capabilities. Second, the stability of H4SO5 very strongly depends on the solvent water being very acidic; the H2SO4–methanol solution is apparently not as acidic. In summary, as indeed should be a priori expected, sulfuric acid in methanol fully conforms to the conventional structure and ion speciation of the dissolved acid as H2SO4, but the aqueous acid behaves otherwise, dissociating as a triprotic acid and fully following a strong 1–3 electrolyte’s thermodynamics.
Quality and hydrogeochemistry appraisal for groundwater in Tenth of Ramadan Area, Egypt
Published in Water Science, 2020
Lubna A. Ibrahim, Eman R. Nofal
On the further hand, carbonate ion speciation for all sites, Table 3, showed that the main aqueous species is HCO3−> H2CO3> CO32-(relying on the pH). The combined metal carbonates will constitute only 2.7%, 2.9% and 9.1% of the aqueous carbon in site 1, site 2 and site 3, respectively, and thus don’t have any real effect on carbonate speciation. The sulfate speciation showed that the major aqueous form of sulfate is free sulfate ion (SO42-). These inorganic species are in the order CaSO4> NaSO4> MgSO4> KSO4 under a variety of conditions. The free ions of NO3− records the following range 97% – 99% of the overall dissolved concentration within the three sites. Chloride ion speciation in the three sites show that the major aqueous form is Cl−, which account more than 99%, 99% and 95% in site 1, site 2 and site 3, respectively. Fluoride ion speciation indicated that 94%, 92% and 80% of the whole species are in the form of F− ion. These results are similar to those given by Falck, Quinn, Duffield, and Williams (1988).