Mok-Ryun Yu

Buffalo weed (Ambrosia trifida L. var. trifida) biochar for cadmium (II) and lead (II) adsorption in single and mixed system.

AbstractBiochars (BWBC 300, BWBC 500 and BWBC 700) derived from buffalo weed (Ambrosia trifida L. var. trifida) at different pyrolysis temperatures of 300, 500 and 700°C were investigated for the removal of Cd(II) and Pb(II) ions from aqueous solutions. The physicochemical properties of the biochars were studied using FTIR, scanning electron microscopy (SEM), X-ray diffraction, Brunauer, Emmett and Teller surface area, cation exchange capacity and energy dispersive X-ray analysis. The adsorption at solution pH = 5 could be well described by Freundlich model for Cd(II) and Pb(II) in their single and mixed system with R2 ⩾ 0.95. The maximum adsorption capacities of the biochar BWBC 700 from the Langmuir equation were found to be 11.63 and 333.33 mg g−1 for Cd(II) and Pb(II), respectively. Pseudo-second-order kinetic model was fitted well in describing the adsorption kinetics of Cd(II) and Pb(II) onto the biochar BWBC 700. About 0.02 mol L−1 disodium salt of EDTA was able to desorb Cd(II) and Pb(II) from the...

Application of Fe(VI) in the treatment of Zn(II)‐NTA complexes in aqueous solutions

The higher oxidation state of iron, i.e. Fe(VI), was exploited to treat the synthetic wastewater containing Zn(II)‐NTA. The decomposition of Zn(II)‐NTA by Fe(VI) was investigated with the help of analytical data obtained for the change in Fe(VI) concentration, dissolved organic carbon (DOC) and total soluble Zn(II) concentration as a function of time at various concentrations of Zn(II)‐NTA and at constant Fe(VI) concentration. The UV‐Visible data was used to explain the reaction kinetics for redox reactions between Fe(VI) and Zn(II)‐NTA. The pseudo‐first‐order rate constant was calculated keeping the Zn(II)‐NTA concentration in excess and hence the overall second‐order‐rate constant was obtained. Fe(VI) reduction was almost unaffected with the 1000 times increase in ionic strength (NaNO3), as well as in the presence of completely oxidized background electrolytes. However, Fe(VI) reduction was greatly affected in the presence of both SO3 2− and NO2 − especially at higher concentrations, indicating a competitive reduction took place between Zn(II)‐NTA and Na2SO3 or NaNO2 in the Fe(VI) treatment. These results were again supported by the dissolved organic carbon observations since relatively very low removal of the dissolved organic carbon occurred in the presence of Na2SO3 and NaNO2.

Treatment of wastewater contaminated with Cd(II)–NTA using Fe(VI)

Abstract The aim of the present investigation is to assess the applicability of Fe(VI) in the treatment of simulated wastewater contaminated with Cd(II)–nitrilotriacetic acid (NTA) soluble species as a cleaner and greener treatment technology. Initially, the degradation of NTA was observed in a single system treatment reactor that applied varied doses of NTA. Results were correlated with the change in Fe(VI) concentration measured by UV–visible spectrophotometer. As a next step, the Fe(VI) was introduced in the reaction reactor containing Cd(II)–NTA species as to investigate the degradation of NTA measured with the help of change in total organic carbon (TOC). The NTA degradation was observed by using the TOC values obtained at different time intervals at pH 10.0. Moreover, the treated samples were subjected to the change in total cadmium concentration as to observe the simultaneous removal of cadmium from the aqueous solutions. The reactivity of the Fe(VI) was also assessed varying the pH from 8.0 to 12....

Removal of arsenic from aqueous solution by iron-coated sand and manganese-coated sand having different mineral types

In this study, the effects of the coating temperature during the preparation of manganese-coated sand (MCS) and iron-coated sand (ICS) on the removals of As(III) and As(V) were evaluated. The mineral type of manganese oxide on MCS-150, prepared at 150 °C, was identified as a mixture of pyrolusite and ramsdellite, which changed to high crystalline pyrolusite above 300 °C. The mineral type of ICS-150, prepared at 150 °C, was a mixture of goethite and hematite, which changed to high crystalline goethite above 300 °C. The adsorption efficiency was determined according to the mineral type which depended on the coating temperature. The As(III) oxidation efficiency of MCS-150 and As(V) adsorption efficiency of ICS-150 were approximately 77 and 70% higher compared with those of MCS-600 and ICS-600, respectively, prepared at 600 °C. Regardless of the coating temperature, the amounts of manganese and iron coated on the sand substrates were similar.

Application of activated carbon impregnated with metal oxides to the treatment of multi-contaminants

In this study, as a novel technique for the simultaneous treatment of As(III) and phenol in a single column reactor, different ratios of manganese-impregnated activated carbon (Mn-AC) and iron-impregnated activated carbon (Fe-AC) were applied in a bench-scale column reactor. In this bench-scale test, the column system packed with both Mn-AC and Fe-AC (binary system) was identified as the best system due to the good oxidation efficiency of As(III) to As(V) by Mn-AC, which reasonably controlled the mobility of total arsenic through adsorption of As(V), along with efficient removal of phenol. When the pilot-scale column reactor, packed with equal amounts of Mn-AC and Fe-AC, was applied for the removal of As(III) and phenol, the oxidation of As(III) by 1 g of Mn-AC for up to 110 days and the removal of phenol by total 1 g of Mn-AC and Fe-AC for up to 100 days were 1.81×10−4 g and 8.20×10−4 g, respectively. Based on this work, Fe-AC and Mn-AC can be regarded as a promising filter material in the treatment of wastewater contaminated with organic compounds, such as phenol, and redox-sensitive ions, such as As(III).

Oxidation of sulphide in abandoned mine tailings by ferrate

In this study, Fe(VI) was applied to treat three mine tailings containing different amounts of sulphides and heavy metals. Oxidation of sulphides by Fe(VI) was studied at pH 9.2 with variation of solid to solution ratio, Fe(VI) concentration and injection number of Fe(VI) solution. The major dissolved products from the treatment of mine tailings with Fe(VI) solution were sulphate and arsenic. Oxidation efficiency of sulphides was evaluated by reduction efficiency of Fe(VI) as well as by measurement of dissolved sulphate concentration. Even though inorganic composition of three mine tailings was different, reduction fraction of Fe(VI) was quite similar. This result can suggest that Fe(VI) was involved in several other reactions in addition to oxidation of sulphides. Oxidation of sulphides in mine tailing was greatly dependent on the total amount of sulphides as well as kinds of sulphides complexed with metals. Over the five consecutive injections of Fe(VI) solution, dissolved sulphate concentration was greatly decreased by each injection and no more dissolved sulphate was observed at the fifth injection. While dissolved arsenic was decreased lineally up to the fifth injection. Sulphate generation was slightly increased for all mine tailings as Fe(VI) concentration was increased; however, enhancement of oxidation efficiency of sulphides was not directly proportional to the initial Fe(VI) concentration.