Chang Gu Lee

Lead and copper removal from aqueous solutions using carbon foam derived from phenol resin

Phenolic resin-based carbon foam was prepared as an adsorbent for removing heavy metals from aqueous solutions. The surface of the produced carbon foam had a well-developed open cell structure and the specific surface area according to the BET model was 458.59m(2)g(-1). Batch experiments showed that removal ratio increased in the order of copper (19.83%), zinc (34.35%), cadmium (59.82%), and lead (73.99%) in mixed solutions with the same initial concentration (50mgL(-1)). The results indicated that the Sips isotherm model was the most suitable for describing the experimental data of lead and copper. The maximum adsorption capacity of lead and copper determined to Sips model were 491mgg(-1) and 247mgg(-1). The obtained pore diffusion coefficients for lead and copper were found to be 1.02×10(-6) and 2.42×10(-7)m(2)s(-1), respectively. Post-sorption characteristics indicated that surface precipitation was the primary mechanism of lead and copper removal by the carbon foam, while the functional groups on the surface of the foam did not affect metal adsorption.

Application of carbon foam for heavy metal removal from industrial plating wastewater and toxicity evaluation of the adsorbent

Electroplating wastewater contains various types of toxic substances, such as heavy metals, solvents, and cleaning agents. Carbon foam was used as an adsorbent for the removal of heavy metals from real industrial plating wastewater. Its sorption capacity was compared with those of a commercial ion-exchange resin (BC258) and a heavy metal adsorbent (CupriSorb™) in a batch system. The experimental carbon foam has a considerably higher sorption capacity for Cr and Cu than commercial adsorbents for acid/alkali wastewater and cyanide wastewater. Additionally, cytotoxicity test showed that the newly developed adsorbent has low cytotoxic effects on three kinds of human cells. In a pilot plant, the carbon foam had higher sorption capacity for Cr (73.64 g kg(-1)) than for Cu (14.86 g kg(-1)) and Ni (7.74 g kg(-1)) during 350 h of operation time. Oxidation pretreatments using UV/hydrogen peroxide enhance heavy metal removal from plating wastewater containing cyanide compounds.

Arsenic(V) removal using an amine-doped acrylic ion exchange fiber: Kinetic, equilibrium, and regeneration studies

This study investigates As(V) removal from aqueous solutions using a novel amine-doped acrylic ion exchange fiber. The amine doping reaction was confirmed using FT-IR, and the surface of the fiber was characterized using FEG-SEM. The synthesis process was completed within 60min using an AlCl3·6H2O catalyst at 100°C, and the resulting in a fiber with an ion exchange capacity of 7.5meq/g. The removal efficiency of the A-60 fiber was affected by the solution pH, and the efficiency was optimum at pH 3.04. As(V) adsorption on the fiber was rapid in the first 20min and reached equilibrium in 60min. As(V) removal followed pseudo-first-order kinetics, and the Redlich-Peterson adsorption isotherm model provided the best fit of the equilibrium data. The fiber has an As(V) adsorption capacity (qe) of 205.32±3.57mg/g, which is considerably higher than literature values and commercial adsorbents. The removal efficiency of the fiber was above 83% of the initial value after nine regeneration cycles.

Effect of nitrogen doping on titanium carbonitride-derived adsorbents used for arsenic removal.

Arsenic in water and wastewater is considered to be a critical contaminant as it poses harmful health risks. In this regard, to meet the stringent regulation of arsenic in aqueous solutions, nitrogen doped carbon-based materials (CN) were prepared as adsorbents and tested for the removal of arsenic ion from aqueous solutions. Nitrogen-doped carbon (CNs) synthesized by chlorination exhibited well-developed micro- and small meso-pores with uniform pore structures. The structure and characteristics of the adsorbents thus developed were confirmed by field-emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. Among the CNs developed, CN700 exhibited high adsorption capacity for arsenic (31.08 mg/g). The adsorption efficiency for arsenic ion was confirmed to be affected by pyrrolic nitrogen and micro-pores. These results suggest that CNs are useful adsorbents for the treatment of arsenic, and in particular, CN700 demonstrates potential for application as an adsorbent for the removal of anionic heavy metals from wastewater and sewage.

Evaluation of sediment capping with activated carbon and nonwoven fabric mat to interrupt nutrient release from lake sediments

The aim of this study was to assess the potential application of activated carbon (AC) and nonwoven fabric mats (NWFM) for thin-layer capping in remediation of sediments containing high amounts of carbon, nitrogen, and phosphorus. Laboratory column incubation experiments were performed to analyze the efficiencies of AC and NWFM for blocking nutrients. Under uncapped conditions, dissolved oxygen (DO) was exhausted within three days but under NWFM/AC capping conditions (with NWFM above the AC capping layer), the presence of DO was prolonged until Day 33. Chemical oxygen demand (COD) was lower under all capped conditions than under uncapped conditions, with lowest COD observed with NWFM/AC capping. NH4-N occupied the highest percentage of total nitrogen in the overlying water and its percentage increased as the DO concentration decreased. The capping efficiencies for NH4-N, T-N, and PO4-P with NWFM/AC capping were (66.0, 54.2, and 73.1) %, respectively, which were higher than for other capping conditions. In the case of T-P, capping efficiencies under all capping conditions were almost 100%, indicating that both AC and NWFM effectively interrupted phosphorus release from sediments. Placing NWFM above the AC capping layer was more effective than the opposite arrangement. It can be concluded that NWFM and AC can be successfully used for remediation of lake sediments with high amounts of nitrogen and phosphorus.

Surface functionalization of mesoporous silica MCM-41 with 3-aminopropyltrimethoxysilane for dye removal: kinetic, equilibrium, and thermodynamic studies

AbstractMesoporous silica MCM-41 was synthesized and functionalized with a silane coupling agent (3-aminopropyltrimethoxysilane, APTMS) for the removal of Acid Blue 25 (AB25, anionic dye) and Methylene Blue (MB, cationic dye) from aqueous solutions as adsorbents. The synthesized (MCM-41) and functionalized (f-MCM-41) materials were characterized using field emission scanning electron microscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, particle size analysis, nitrogen gas adsorption-desorption analysis, X-ray diffraction spectrometry, and Fourier transform infrared spectrometry. The results indicate that the surface modification of MCM-41 with APTMS was successfully carried out. Batch experiments were performed to examine AB25 and MB removal by MCM-41 and f-MCM-41 under various experimental conditions. The results show that f-MCM-41 was a good adsorbent for anionic AB25, but not for cationic MB. This could be attributed to the presence of amine groups on the surfaces of f-MC...

Evaluation of the Use of Sea Sand, Crushed Concrete, and Bentonite to Stabilize Trace Metals and to Interrupt Their Release from Contaminated Marine Sediments

The aim of this study is to assess the effectiveness of sea sand (SS), crushed concrete (CC), and bentonite (BN) as a capping material to block the release of trace metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) from heavily contaminated marine sediments, and to stabilize/solidify these trace metals in the sediments. The efficiency of SS, CC, and BN for blocking trace metals was evaluated in a flat flow tank in which a 1-cm-thick layer of capping materials was placed above the contaminated sediments. Trace metals were released into the overlying water from contaminated sediments in the following decreasing order: Cd > As > Zn > Ni > Pb > Cr > Cu. Electronegativity, electrostatic force, or metal hydrolysis significantly influenced the mobility of trace metals in sediments. The elution of Cu, Ni, and Cd from contaminated sediments was effectively reduced by CC, especially in case of Cd elution. SS was appropriate for interrupting Cr and Zn release, and BN was appropriate for interrupting Pb release. A sequential extraction study demonstrated that SS capping is appropriate for stabilizing As, Cu, and Ni; CC capping for Zn; and BN capping for Pb. SS, CC, and BN can be applied effectively for remediating the contaminated sediments.

Comparative analysis of fixed-bed sorption models using phosphate breakthrough curves in slag filter media

AbstractFixed-bed kinetic sorption (Bohart–Adams, Thomas, Yoon–Nelson, Clark, Wolborska, and modified dose-response) models are commonly used to simulate breakthrough curves (BTCs) from fixed-bed systems. However, more caution should be taken in using these models. Some researchers misused the equation, which is a totally different type from the original model, as a simplified model. Others used the same equation expressed in different forms as an independent model. The aim of this study was to clarify the fixed-bed sorption models via comparative analysis using the phosphate BTCs in slag filter media. For the analysis, the breakthrough data for phosphate (initial phosphate concentration = 1.0 and 2.0 mg/L) sorption in fixed-bed columns (inner diameter = 2.5 cm and column length = 10, 20, and 30 cm) were obtained from the experiments. The original Bohart–Adams model was simplified in the literature to the convergent- and divergent-type models in order to be used for the BTC analysis. However, the divergen...

Adsorption of bacteriophage MS2 to magnetic iron oxide nanoparticles in aqueous solutions

The aim of this study was to investigate the adsorption of bacteriophage MS2 by magnetic iron oxide nanoparticles in aqueous solutions. The characteristics of synthetic nanoparticles were analyzed using various techniques. The adsorption of MS2 to the nanoparticles was examined under various conditions using batch experiments. The results showed that the nanoparticles were mainly composed of maghemite along with goethite. The nanoparticles had a specific surface area of 82.2 m2 g−1, with an average pore diameter of 13.2 nm and total pore volume of 0.2703 cm3 g−1. The results demonstrated that the removal of MS2 by the nanoparticles was very fast. A 3.15 log removal (99.93%) was achieved within 60 min (adsorbent dose = 2 g L−1; MS2 concentration = 2.94 × 106 pfu mL−1). The log removal decreased from 3.52 to 0.36 with increasing MS2 concentration from 1.59 × 104 to 5.01 × 107 pfu mL−1. Also, the effect of solution pH on MS2 removal was minimal at pH 4.2–8.4. The removal of MS2 decreased in the presence of anions such as carbonate and phosphate, with the latter showing a greater hindrance effect on removal. This study demonstrated that magnetic iron oxide nanoparticles are very effective in the removal of MS2 from aqueous solutions.

Lab-scale experiments and model analyses for bacterial removal in flow-through columns containing dolomite

AbstractThe aim of this study was to investigate the removal of bacteria (Bacillus subtilis ATCC 6633) from aqueous solutions using dolomite as a filter medium. Column experiments were performed in step injection mode under various conditions of influent bacterial concentration (0.5–2.0 g/L), flow rate (0.5–1.5 mL/min), and column length (10–30 cm). The highest percentage bacterial removal (Re) of 75.2 ± 1.6% was obtained under the following conditions: influent bacterial concentration = 1.0 g/L; flow rate = 0.5 mL/min; column length = 20 cm. The highest column capacity for bacterial removal (q0) of 2.126 ± 0.067 mg/g was achieved using an influent bacterial concentration of 2.0 g/L, flow rate of 1.0 mL/min, and column length of 20 cm. Increasing the bacterial concentration and flow rate had a negative effect on Re, whereas the q0 values were positively affected. Increasing the column length produced a positive effect on Re, whereas q0 declined. Simulation of the breakthrough curves (BTCs) using the Adams...