Won Sik Shin

APPLICATION OF SYNTHETIC POLYAMINE FLOCCULANTS FOR DYE WASTEWATER TREATMENT

Polyamine flocculants were synthesized and applied for the removal of color, turbidity, and organic compounds from dye wastewater. The effect of polyamine on color removal was investigated by comparing 2 treatments: 1) alum alone and 2) alum/polyamine in combination. The effects of polyamine flocculant, concentration, types, and pH on the removal efficiency of colored materials were investigated. Polyamine flocculants were highly efficient in the removal of color and turbidity from dye wastewater. Compared with alum alone treatment, an addition of 25 mg/L of polyamine could reduce alum dosage by more than 50% and improve the color and turbidity removal efficiency. Highly efficient color removal was obtained by adding polyamine as a flocculant at widely different pH ranges. Results indicate that the use of polyamine flocculant is cost effective in dye wastewater treatment because it minimizes the amount of sludge produced as the dosage of inorganic coagulant is highly reduced. Effects of zeta potential and pH are also discussed in the paper.

Diffusive gradients in thin films (DGT) for the prediction of bioavailability of heavy metals in contaminated soils to earthworm (Eisenia foetida) and oral bioavailable concentrations

The applicability of diffusive gradients in thin-films (DGT) as a biomimic surrogate was investigated to determine the bioavailable heavy metal concentrations to earthworm (Eisenia foetida). The relationships between the amount of DGT and earthworm uptake; DGT uptake and the bioavailable concentrations of heavy metals in soils were evaluated. The one-compartment model for the dynamic uptake of heavy metals in the soil fitted well to both the earthworm (R(2)=0.641-0.990) and DGT (R(2)=0.473-0.998) uptake data. DGT uptake was linearly correlated with the total heavy metal concentrations in the soil (aqua regia), the bioavailable heavy metal concentrations estimated by fractions I+II of the standard measurements and testing (SM&T) and physiologically based extraction test (PBET, stomach+intestine). The coefficients of determination (R(2)) of DGT uptake vs. aqua regia were 0.433, 0.929 and 0.723; vs. SM&T fractions (I+II) were 0.901, 0.882 and 0.713 and vs. PBET (stomach+intestine) were 0.913, 0.850 and 0.649 for Pb, Zn and Cu, respectively. These results imply that DGT can be used as a biomimic surrogate for the earthworm uptake of heavy metals in contaminated soils as well as predict bioavailable concentrations of heavy metals estimated by SM&T (I+II) and PBET as a human oral bioavailable concentrations of heavy metals.

Reductive denitrification using zero‐valent iron and bimetallic iron

A study of reductive denitrification of nitrate was conducted. Microscale zero‐valent iron (ZVI) and palladium‐coated iron (Pd/Fe) were used in the reduction of nitrate with variable pH. The solution pH was controlled by an auto controlling system instead of chemical buffers. Higher reduction rates were achieved with lower pH and lower pH gave the pseudo‐first‐order kinetics while it was close to the zero‐order reaction when the pH of the solution was becoming high and nitrate concentration was higher. As it took several hours to convert intermediates to ammonia completely, the assumption, under which mass loss calculated from the measured ammonia concentration right after the reaction was the mass of nitrogen evolved, could lead to overestimation of the nitrogen selectivity. The current study confirmed that the palladium coating on the iron could increase the nitrogen selectivity, and the Pd/Fe system could also achieve the advantages of coupling of electron source and catalyst with regard to the engineering aspects.

Assessment of metal bioavailability in smelter-contaminated soil before and after lime amendment.

In this study, changes in bioavailable concentrations of Pb, Zn, Cu and As in former smelter site soils (J1 and J2) were investigated before and after lime amendment. The immobilization efficiencies of metal(loid)s were evaluated by Toxicity Characteristic Leaching Procedure (TCLP). Their bioavailable concentrations in the soils were evaluated by the acid-extractable and -reducible fractions in Standard Measurement and Testing Program (i.e., SM&T(I+II)), in vitro physiologically based extraction test (PBET) and diffusive gradients in thin-films (DGT). The results showed that the bioavailable concentrations remarkably decreased after lime amendment in both J1 and J2 soils. DGT uptake and resupply (R) of Zn, Cu and As from soil to soil solution increased but that of Pb decreased. This pattern was consistent with SM&T(I+II)- and PBET-extractable concentrations after lime amendment. This indicates that lime amendment is highly effective for the immobilization of Zn, Cu and As, but not for Pb. Our results implicate that DGT can be used to estimate bioavailability of metal(loid)s in soils and further extended to estimate risk reduction after soil remediation.

A simple mathematical analysis on the effect of sand in Cr(VI) reduction using zero valent iron

A simple mathematical model was proposed to analyze the enhancement of Cr(VI) reduction when sand materials are added to the zero valent iron (ZVI). Natural decay of Cr(VI) in a control experiment was analyzed by using a zero-order decay reaction. Adsorption kinetics of Cr(VI) to sand was modeled as a first-order reversible process, and the reduction rate by ZVI was treated as a first-order reaction. Natural decay of Cr(VI) was also included in other experiments, i.e., the adsorption to sand, the reduction by ZVI, and both adsorption and reduction when sand and ZVI are present together. The model parameters were estimated by fitting the solution of each model to the corresponding experimental data. To observe the effect of sand addition to ZVI, both adsorption and reduction rate models were considered simultaneously including the natural decay. The solution of the combined model was fitted to the experimental data to determine the first-order adsorption and reduction rate constants when sand as well as ZVI is present. The first-order reduction rate constant in the presence of sand was about 35 times higher than that with ZVI only.

Reductive dechlorination of chlorinated biphenyls by palladized zero-valent metals.

Abstract Laboratory-scale reductive dechlorination studies using bimetals were conducted to detoxify chlorinated biphenyls, which are known as one of the most recalcitrant organic compounds. Palladized iron and palladized zinc readily dechlorinated mono- and di-chlorinated biphenyls while plain metals were not active. Biphenyl and less chlorinated biphenyls were detected as the major products and calculated mass balance was around 100%, indicating that predominant degradation reaction was dechlorination. For Pd/Fe, degradation rates of mono-chlorobiphenyls were higher than those of di-chlorobiphenyls. Pd/Zn showed higher reactivity than Pd/Fe for the degradation of chlorobiphenyls. Degradation rates of three mono-chlorobiphenyls were in order of 4-CBP > 3-CBP > 2-CBP and this order was matched with the selectivity and dechlorination rate of dichlorobiphenyls. Based on the detected daughter products, it was considered that degradation reaction of dichlorobiphenyls was mainly governed by stepwise dechlorination. However, sequential reaction model fittings indicated that concerted dechlorination was also partly involved in the dichlorobiphenyl degradation. This study demonstrated that catalytically modified ZVM could be successfully applied for the detoxification of chlorinated aromatic compounds including PCBs.

Competitive sorption of anionic and cationic dyes onto cetylpyridinium-modified montmorillonite

Single-and multi-solute competitive sorptions of anionic dyes; Eriochrome Black T (EBT), Orange II (OR) and Methyl Orange (MO) and cationic dyes; Thioflavin T (TT), Methylene Blue (MB) and Crystal Violet (CV) onto montmorillonite modified with a cationic surfactant, cetylpyridinium chloride (CP), were investigated. In single-solute sorption, the sorption affinity, as represented by Freundlich sorption coefficient (K F) and Langmuir sorption capacity (q mL ), was in the order of EBT > OR > MO for anionic dyes and in the order of TT > MB > CV for cationic dyes. The sorption affinity of the cationic dye was higher than that of the anionic dye mainly due to the difference in sorption mechanisms: ion exchange to the bare montmorillonite surface plus two dimensional surface adsorption onto the pseudo-organic medium formed by the conglomeration of the long-chain hydrocarbon tail groups of the CP cation on the montmorillonite for cationic dyes vs. two dimensional surface adsorption only for anionic dyes. Three-parameter models (dual-mode and Song models) fitted better than the two-parameter models (Freundlich, Langmuir and Dubinin-Radushkevich models) due to the number of parameters involved. The conventional Dubinin-Radushkevich (D-R) model often used to classify sorption mechanisms based on the mean free energy were not able to explain the higher sorption of cationic dyes than anionic dyes. Among the tested models, the Song model was the best in predicting single-solute sorption in terms of the coefficient of determination (R2) and the sum of squared errors (SSE) values. Although both dual-mode and Song models fitted well to the sorption data, the results of asymptotic behavior analyses showed that Song model was better than dual-mode model in predicting sorption behaviors and in explaining sorption mechanisms. Competition between the solutes in the bisolute and trisolute system reduced the sorbed amount of each solute compared with that in the single-solute system. Generally the ideal adsorbed solution theory (IAST) coupled to the single-solute sorption model predicted the bisolute and tri-solute competitive sorption data favorably except a few bisolute systems.

Nutrient enhanced biodegradation of crude oil in tropical salt marshes

Tropical salt marshes in Louisiana are at risks ofaccidental oil spills and remediation of these ecosystemsis mainly limited to natural biodegradation due tophysical sensitivity of the ecosystems. This studyinvestigated both intrinsic and nutrient enhanced ratesof crude oil degradation in core studies. In addition,loading rates of nitrogen and optimal porewater nitrogenconcentrations were determined. Nitrogen additionsincreased biodegradation rates of some alkanes andpolycyclic aromatic hydrocarbons (PAHs). Addition ofNH4+-N increased zero-order mineralizationconstants of labeled hexadecane and phenanthrene up to15.4–19.2% (Fourchon marsh) and 56.2% (Ugly Shack Bayoumarsh) and rates of total carbon dioxide production up to14.0–33.1% (Fourchon marsh) and 3.0% (Ugly Shack Bayoumarsh), respectively. Efficient biodegradation of crudeoil was achieved when NH4+ was applied at theloading rate of 28.3–56.6 g N m-2 producing porewaterconcentration at the level of 80–450 mg NH4+-N L-1. No significant lag time was observed indicating thatnitrogen application directly stimulates biodegradationof crude oil in tropical salt marshes in Louisiana.

Adsorptive Removal of Co and Sr Ions from Aqueous Solution by Synthetic Hydroxyapatite Nanoparticles

Hydroxyapatite nanoparticles were synthesized by using the precipitation method with simulated body fluid solution and applied for adsorption of Co2+ and Sr2+ in aqueous solution. The single- and bi-solute adsorption experiments were performed to evaluate the maximum adsorption capacity of hydroxyapatite nanoparticles for Co2+ and Sr2+, the effect of temperature and pH, and the influence of simultaneous presence of other competing metal ion in a binary system. The synthesized hydroxyapatite nanoparticles had high adsorption capacity for Co2+ and Sr2+ due to a high specific surface area. The maximum adsorption capacity and binding energy of Co2+ were higher than those of Sr2+ in single-solute adsorption. The extended Langmuir model was fitted well for bi-solute competitive adsorption of Co2+ and Sr2+ onto the hydroxyapatite nanoparticles. Thermodynamic analysis showed that adsorption occurred spontaneously for both metals and was endothermic for Co2+, but exothermic for Sr2+.

Improvement of Water Treatment Performance by Using Polyamine Flocculants

In this study, polyamine flocculants were synthesized and applied to Nak-dong river raw water in Korea to examine their efficiency in reducing turbidity, total organic carbon (TOC) and UV254. Synthesized polyamines were effective as flocculants for water treatment and the addition of organic polymer caused a reduction of 50-80% of the consumption of polyaluminium chloride (PAC). The effects of polyamine on the removal of turbidity, TOC and UV254 were investigated via both jar and pilot tests. The adsorption and separation mechanisms for the removal of turbidity and TOC by using the polymer flocculants were also observed.