Sang June Choi

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.

Removal of ammonia by biofilters: a study with flow-modified system and kinetics.

Abstract The characteristics of ammonia removal by two types of biofilter (a standard biofilter with vertical gas flow and a modified biofilter with horizontal gas flow) were investigated. A mixture of organic materials such as compost, bark, and peat was used as the biofilter media based on the small-scale column test for media selection. Complete removal capacity, defined as the maximum inlet load of ammonia that was completely removed, was obtained. The modified biofilter showed complete removal up to 1.0 g N/kg dry material/day. However, the removal capacity of the standard biofilter started to deviate from complete removal around 0.4 g N/kg dry material/day, indicating that the modified biofilter system has higher removal efficiency than the standard upflow one. In kinetic analysis of the biological removal of ammonia in each biofilter system, the maximum removal rate, V m , was 0.93 g N/kg dry material/day and the saturation constant, K s , was 32.55 ppm in the standard biofilter. On the other hand, the values of V m and K s were 1.66 g N/kg dry material/day and 74.25 ppm, respectively, in the modified biofilter system.

Improvement of Flocculation Efficiency of Water Treatment by using Polymer Flocculants

As water treatment plants have to supply water with satisfactory quality, timely responses to fluctuations in raw water quality are of importance. In most cases, metal salts type inorganic flocculants have been sufficient to maintain the water quality. However, due to various reasons there are situations where metal salts cannot solve the problem caused by the poor quality of inflow water. In this study, organic polymers such as polyamine and poly(diallyldimethylammonium chloride(DADM)) were synthesized and were applied to Nak-dong river raw water in Korea to check their efficiency in reducing turbidity and total organic carbon (TOC). Synthesized polyamine and poly(DADM) flocculants were effective as flocculants for water treatment and the addition of 1 mg l−1 of organic polymer caused a reduction of 50 % of the consumption of polyaluminium chloride (PAC). The effects of polymer, polymer amount, initial turbidity, and pH on the removal of turbidity and TOC were investigated. The adsorption and separation ...

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.

Effect of Polyamine Flocculant Types on Dye Wastewater Treatment

Linear, branched, and grafted polyamine flocculants were synthesized and applied for dye wastewater treatment. The effect of polyamines on color removal was investigated by comparing two treatments: (i) alum alone and (ii) alum/polyamine in combination. Compared to alum alone treatment, the use of polyamine flocculants in combination with alum was highly efficient in color and turbidity removal. Addition of a small amount of polyamine (40 mg/L) reduced alum dosage by 50% while improving color removal efficiency by 20%. Branched polyamines were more efficient than grafted polyamines presumably because branched polyamine has higher charge density than grafted polyamine. Our results indicate that the use of alum/polyamine system is beneficial in dye wastewater treatment. The effects of polyamine flocculants on total organic carbon removal and zeta potential were also discussed.

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.

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.

Removal of Direct Red from Aqueous Solution by Foam Separation Techniques of Ion and Adsorbing Colloid Flotation

Abstract Experimental investigations on the removal of Direct Red from an aqueous solution were carried out through two foam separation techniques: ion flotation and adsorbing colloid flotation with Fe(III). The residual concentration of Direct Red can be lowered to below 0.5 ppm in 3 minutes by ion flotation and below 0.1 ppm in 2 minutes by adsorbing colloid flotation. The optimum pH for the removal of Direct Red was found to be 4 for ion flotation and 3–5 for adsorbing colloid flotation. The effects of surfactant, foreign ions, and Al(III) addition on the removal of Direct Red are discussed.

Application of Synthetic Poly(DADM) Flocculants for Dye Wastewater Treatment

Poly(DADM) flocculants were synthesized and applied for the removal of color, turbidity and organic materials from dye wastewater. The effect of poly(DADM) on color removal was investigated by comparing two treatments: (i) alum alone and (ii) alum/poly(DADM) in combination. The effects of poly(DADM) flocculant, poly(DADM) concentration, poly(DADM) types and pH on the removal efficiency of coloring materials were investigated. Poly(DADM) flocculants were highly efficient in the removal of color and turbidity from dye wastewater. Compared to treatment with alum alone, the addition of a small amount of poly(DADM) (25 mg l−1) reduced alum dosage by 50% while improving color removal efficiency. Highly efficient color removal was obtained in wide pH ranges by adding poly(DADM) as a flocculant. Our results indicate that the use of poly(DADM) flocculant is cost effective in dye wastewater treatment by reducing sludge production and the dosage of inorganic coagulant. Effects of zeta potential were also investigated.

Sequential competitive sorption and desorption of chlorophenols in organoclay

Single- and bi-solute sorption and desorption of 2-chlorophenol (2-CP) and 2,4,5-trichlorophenol (2,4,5-TCP) in montmorillonite modified with hexadecyltrimethyl-ammonium (HDTMA) were investigated by sequential sorption and desorption. Effect of pH on the sequential sorption and desorption was investigated. As expected by the magnitude of octanol: water partition coefficient (Kow), both sorption and desorption affinity of 2,4,5-TCP was higher than that of 2-CP at pH 4.85 and 9.15. For both chlorophenols, the protonated speciation (at pH 4.85) exhibited a higher affinity in both sorption and desorption than the predominant deprotonated speciation (about 80% and 99% of 2-chlorophenolate and 2,4,5-trichlophenolate anions at pH 9.15, respectively). Desorption of chlorinated phenols was strongly dependent on the current pH regardless of their speciation in the previous sorption stage. Freundlich model was used to analyze the single-solute sorption and desorption data. No appreciable desorption-resistant (or non-desorbing) fraction was observed in organoclays after several sequential desorptions. This indicates that sorption of phenols in organoclay mainly occurs via partitioning into the core of the pseudo-organic medium, thereby causing desorption nearly reversible. In bisolute competitive systems, sorption (or desorption) affinity of both chlorophenols was reduced compared to that in its single-solute system due to the competition between the solutes. The ideal adsorbed solution theory (IAST) coupled with the single-solute Freundlich model was positively correlated with the bisolute sequential competitive sorption and desorption equilibria.