Seung Mok Lee

Removal of heavy metals using waste eggshell

The removal capacity of toxic heavy metals by the reused eggshell was studied. As a pretreatment process for the preparation of reused material from waste eggshell, calcination was performed in the furnace at 800 degrees C for 2 h after crushing the dried waste eggshell. Calcination behavior, qualitative and quantitative elemental information, mineral type and surface characteristics before and after calcination of eggshell were examined by thermal gravimetric analysis (TGA), X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. After calcination, the major inorganic composition was identified as Ca (lime, 99.63%) and K, P and Sr were identified as minor components. When calcined eggshell was applied in the treatment of synthetic wastewater containing heavy metals, a complete removal of Cd as well as above 99% removal of Cr was observed after 10 min. Although the natural eggshell had some removal capacity of Cd and Cr, a complete removal was not accomplished even after 60 min due to quite slower removal rate. However, in contrast to Cd and Cr, an efficient removal of Pb was observed with the natural eggshell rather than the calcined eggshell. From the application of the calcined eggshell in the treatment of real electroplating wastewater, the calcined eggshell showed a promising removal capacity of heavy metal ions as well as had a good neutralization capacity in the treatment of strong acidic wastewater.

Effect of the N/P ratio on biomass productivity and nutrient removal from municipal wastewater

The aim of this study is to investigate the effect of the N/P ratio on biomass growth with the simultaneous removal of nutrients from municipal wastewaters. An optical panel photobioreactor is employed for this investigation because it provides a uniform light distribution within the reactor, which enhances the efficiency of the reactor in the cultivation of microalgae. The N/P ratio is varied over a wide range, i.e., from 5 to 30, for the assessment of its effect on biomass productivity. There is not a strong correlation between biomass productivity and TN removal, and these factors do not seem to be proportional in the wastewater using the microalgae we employed. In contrast, the TP removal depends greatly on both the N/P ratio and biomass productivity. The optimum value of the N/P ratio for biomass productivity in and nutrient removal from municipal wastewater treatment using microalgae varies from 5 to 30, depending on the ecological conditions in the wastewater.

Efficient attenuation of 17α-ethynylestradiol (EE2) and tetracycline using novel hybrid materials: batch and column reactor studies

Hybrid materials were obtained by modifying natural bentonite (B) or locally collected clay (LC) using hexadecyltrimethylammonium bromide (HDTMA) to obtain bentonite-HDTMA (BH) and local clay-HDTMA (LCH), or by simultaneous pillaring with aluminum and modification with HDTMA to obtain BAH and LCAH. The hybrid materials were used for the efficient attenuation of micro-pollutants, 17α-ethynylestradiol (EE2) and tetracycline (TC), in aqueous solutions under batch and fixed-bed column reactor experiments. Batch data indicated that the uptake of EE2 and TC by the hybrid materials was slightly affected at low and high pH within the pH range of 4.0–10.0. The uptake was not affected by varying the initial sorptive concentration (1.0–10.0 mg L−1 for EE2 and 1.0–20.0 mg L−1 for TC) and the background electrolyte (NaCl) concentrations (0.0001–0.1 mol L−1). Moreover, the attenuation of EE2 and TC by these hybrid materials was fairly efficient. Within a contact time of 60 min for EE2 and 240 min for TC, an apparent equilibrium between the clay and solution was achieved. Kinetic modeling showed that the data were fitted well to the pseudo-second order (PSO) and fractal-like-pseudo-second order (FL-PSO) kinetic models compared with the pseudo-first order (PFO) model because a low value of the least square sum was obtained for these two models. The fixed-bed column results showed that a high breakthrough volume was obtained for attenuation of EE2 and TC using the hybrid materials. Furthermore, the breakthrough data were fitted well to the Thomas equation; therefore, a very high loading capacity was estimated for EE2 and TC for the hybrid materials. These hybrid materials are useful materials in the remediation of aquatic environments contaminated with these two micro-pollutants.

Use of hybrid materials in the decontamination of bisphenol A from aqueous solutions

Hybrid materials were obtained by modifying natural sericite. The sericite was modified with hexadecyltrimethylammonium bromide (HS) and alkyldimethylbenzylammonium chloride (AS) to obtain organo-modified sericites, together with aluminum-H-sericite (AHS) and aluminum-A-sericite (AAS) as inorgano–organo-modified sericite hybrid materials. The hybrid materials were characterized by FT-IR spectrometry, XRD and SEM. The pHPZC values of the solid hybrid materials were obtained by acid–base titration. The Brunauer–Emmett–Teller surface area and pore size of the hybrid materials were also determined. The resulting materials were used in the remediation of waste waters contaminated with bisphenol A (BPA) using batch and column reactor operations. The batch experiments showed that an increase in pH from 2.0 to 10.0 did not affect the percentage uptake of BPA by these hybrid materials, but at pH > 10.0 the percentage uptake of BPA decreased significantly for the AHS and AAS hybrid materials. An increase in the concentration of BPA (1.0–20 mg L−1) and the background electrolyte concentration (0.0001–0.1 mol L−1 NaCl) did not affect the percentage removal of BPA by these hybrid materials. The time dependence adsorption data showed that BPA was quickly taken up onto these hybrid materials as most of the BPA was trapped within the first few minutes of contact. The kinetic data fitted well to a pseudo-second-order and fractal-like pseudo-second-order model rather a pseudo-first-order model. The results of pseudo-second-order fitting showed that the removal capacities of the AS, HS, AAS and AHS hybrid materials for BPA were 4.816, 5.047, 4.874 and 4.856 mg g−1, respectively. In addition, AAS and AHS were used for dynamic studies in column experiments. The breakthrough curves were then used for the non-linear fitting of the Thomas equation. The loading capacity of the column for BPA using the AHS and AAS hybrid materials was estimated.

Clay catalysed rapid valorization of glycerol towards cyclic acetals and ketals

Biodiesel production usually results in a huge amount of glycerol, raising a critical need to transform it into high value products. The present study highlights that solvent-free, conventional thermal activation, and non-conventional microwave/ultrasonic activation in the liquid phase are able to selectively transform glycerol into cyclic acetals and ketals using an optimised acid activated clay catalyst. Several parameters for the acid activation of bentonite clay were optimized under mild reaction conditions with a high concentration of clay (6%) and varying the acid concentration in the range of 6 to 15 N. The acid-activated clay samples were characterized by XRD, FT-IR, BET, and XRF analysis. The active sites of the catalyst were examined by volumetric titration and confirmed by pyridine adsorbed FT-IR and advanced NH3-TPD analyses. The activation performed at relatively mild conditions, i.e.; 6 N H2SO4 and 6% w/v clay, reproducibly resulted in an improved surface area (180 m2 g−1) and surface acidity (23 mg KOH g−1), with superior quantitative Bronsted and Lewis acidic sites. Moreover, the eco-friendly process involving a catalyst, microwave, or ultra-sonication were successfully utilized to achieve a commercially valuable hyacinth fragrance, in addition to furan-based fuel additive precursors exhibiting a high conversion of glycerol and excellent selectivity within much less activation time (2 min).

Heavy metal removal from aqueous solution by tannins immobilized on collagen

Abstract Different recycled materials, which were derived from leather manufacturing processes, were used as adsorbents for the treatment of synthetic wastewater containing heavy metal ions. Three pelt scraps samples (P-M, P-Z and P-P), one shaving scrap (S) and one trimming scrap (T) were used as recycled adsorbents. Removal efficiency of Cu(II), Cd(II), Zn(II), Pb(II) and Cr(III) was evaluated by a laboratory-scale batch reactor at different solution pH. For all adsorbents except T sample, the adsorption of heavy metal ions begins between pH 2 and 4 and reaches near complete adsorption within the next 3–4 pH units, showing a typical cationictype of adsorption. Removal trend of Cr(III) was quite similar without depending on the kind of adsorbents. From the kinetic experiments of Cu(II) by S adsorbent, adsorption of Cu(II) was bett er described by second-order reaction than first-order reaction. The initial removal rate of Cu(II) by S adsorbent was 7143 mg/kg·h. Adsorption isotherm of Cu(II) onto S adsorb...

Electrochemical sensor for trace determination of cadmium(II) from aqueous solutions: use of hybrid materials precursors to natural clays

ABSTRACT A sensitive and efficient electroanalytical method for trace determination of cadmium(II) was developed using hybrid material-modified carbon paste electrodes. The hybrid materials were obtained by modifying the commercial bentonite (BC) and locally collected clay (LC) using the hexadecyltrimethylammonium bromide (HDTMA) as to obtain the organo-modified clay samples (BH and LCH). Moreover, the local clay was pillared with aluminium and modified with the HDTMA (LCAH). The carbon paste electrode was modified with the BC/BCH/LC/LCH/LCAH hybrid materials. Cyclic voltammetric analytical data showed that the modified electrodes were possessed a characteristic reversible behaviour of Cd(II) in aqueous media. Moreover, a significant increase in cathodic or anodic current was obtained using the modified electrodes, BCH, LCH and LCAH. The electroactive surface area of modified electrodes was increased significantly compared to the pristine clay-modified carbon paste electrodes. The response of the modified electrode was not affected significantly varying the pH within the pH region 2.0–10.0. Fairly, a good linearity between the anodic current and concentration of Cd(II) (5.0–40 μg/L) was achieved using the modified electrodes (BCH, LCH and LCAH). The presence of different cations and anions as coexisting ions were studied in order to simulate the real water matrix measurements. Additionally, the real matrix analysis was simulated using the Cd(II) spiked tap water, which showed a good linearity between the concentration of Cd(II) and anodic current.

Nanopillars TiO2 thin film photocatalyst application in the remediation of aquatic environment

We assessed the photocatalytic behavior of Nanopillars-TiO2 thin films obtained onto a borosilicate glass in the degradation of 17α-ethynylestradiol (EE2) from aqueous solution under batch reactor operations. The thin films were characterized by the XRD, SEM, AFM analytical methods. BET specific surface area and pore sizes were also obtained. The photocatalytic degradation of EE2 using the UV light was studied at wide range of physico-chemical parametric studies to determine the mechanism of degradation as well the practical implacability of the technique. The batch reactor operations were conducted at varied pH (pH 4.0 to 10.0), EE2 initial concentration (1.0 to 5.0mg/L) and presence of several interfering ions, i.e., cadmium nitrate, copper sulfate, zinc chloride, sodium chloride, sodium nitrate, sodium nitrite, glycine, oxalic acid and EDTA in the photocatalytic degradation of EE2. The time dependence photocatalytic degradation of EE2 was demonstrated with the pseudo-first-order rate kinetics. The mineralization of EE2 was assessed using the total organic carbon analysis conducted at varied initial pH and EE2 concentrations. Further, the repeated use of the photocatalyst enhanced the applicability of thin films in the successive photocatalytic operations.

Nanocomposite thin films Ag 0 (NP)/TiO 2 in the efficient removal of micro-pollutants from aqueous solutions: A case study of tetracycline and sulfamethoxazole removal

The aim of this communication is to synthesize novel Nanocomposite thin film materials (Ag0(NP)/TiO2) using the template process. Surface morphology of materials was obtained by the Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses. The presence of doped Ag-nanoparticles was confirmed by the TEM images along with the SEM-EDX analyses. The Atomic Force Microscopic images were demonstrated the surface roughness and thickness of Nanocomposite thin films. X-ray diffraction analysis confirmed that TiO2 was predominantly present to its anatase mineral phase. The Fourier Transform Infra-red analysis conducted to obtain the functional groups present with the solid. The specific surface area and pore sizes of Nanocomposites were obtained by the BET (Brunauer, Emmett, and Teller) analysis. Further, the Nanocomposite thin film photocatalysts were successfully employed in the degradation of emerging micro-pollutants viz., the antibiotics tetracycline and sulfamethoxazole from aqueous solutions using less harmful UV-A light (λmax 330 nm). The effect of solution pH (pH 4.0-8.0) and pollutant concentrations (1.0 mg/L-20.0 mg/L (for tetracycline) and (0.5 mg/L-15.0 mg/L (for sulfamethoxazole)) was extensively studied in the photocatalytic removal of these antibiotics. A significant decrease in percentage of non-purgeable organic carbon removal indicated that the micro-pollutants was substantially mineralized by the photocatalytic treatment. The stability of thin film was assessed by the repeated use of Nanocomposite thin films and results were indicated that the degradation of tetracycline or sulfamethoxazole was almost unaffected at least for six cycles of photocatalytic operations. The presence of several cations and anions in the degradation of these antibiotics was studied. Additionally, the presence of 2-propanol and EDTA inhibited significantly the degradation of these micro-pollutants i.e., the percentage of degradation was decreased by 31.8 and 24.2% (for tetracycline) and 42.8 and 39.9% (for sulfamethoxazole), respectively. This indicated that the degradation of tetracycline or sulfamethoxazole was predominantly proceeded by the OH radicals; generated at the valance and conduction band of semiconductor. Similarly, the presence of sodium azide inhibited the percentage removal of these antibiotics.

Chemical and toxicological assessment of arsenic sorption onto Fe-sericite composite powder and beads

Batch sorption and leaching of arsenic (1-30mgL-1) on Fe-sericite composite powder and beads were investigated in this study. Fe-sericite composite powder was made from natural sericite modified with iron, and alginate was used to transform the powder into beads. The maximum sorption capacities of the Fe-sericite composite powder (15.04 and 13.21mgg-1 for As(III) and As(V), respectively) were higher than those of the corresponding beads (9.02 and 7.11mgg-1 for As(III) and As(V), respectively) owing to the higher specific surface area of the powder. In addition, the leaching amounts of As(III) from Fe-sericite composite beads (≤ 15.03%) were higher than those of the corresponding powder (≤ 5.71%). However, acute toxicity of As(III)-sorbed Fe-sericite composite beads toward Daphnia magna was not significantly different from that of the corresponding powder (p > 0.05). Considering higher uptake of the powder particles by the daphnids, Fe-sericite composite beads seem to be a more appropriate and safer sorbent for arsenic removal in practical application. Based on Fe content, Fe-sericite composite beads had similar or higher maximum sorption capacities (71.19 and 56.11mgg-1 Fe for As(III) and As(V), respectively) than those of previously reported sorbents.