• Korean Journal of Environmental Biology
• /
• v.41 no.4
• /
• pp.370-385
• /
• 2023

Cyanobacterial harmful algal blooms (Cyano-HABs) are an international environmental problem that negatively affects the ecosystem as well as the safety of water resources by discharging cyanotoxins. In particular, the discharge of microcystins (MCs), a highly toxic substance, has been studied most actively, and various water treatment methods have been proposed for this purpose. In this paper, we reviewed adsorption technology, which is recognized as the most feasible, economical, and efficient method among suggested treatment methods for removing MCs. Activated carbons (AC) are widely used adsorbents for MCs removal, and excellent MCs adsorption performance has been reported. Research on alternative adsorption materials for AC such as biochar and biosorbents has been conducted, however, their performance was lower compared to activated carbon. The impacts of adsorbent properties(characteristics of pore surface chemistry) and environmental factors (solution pH, temperature, natural organic matter, and ionic strength) on the MCs adsorption performance were also discussed. In addition, toward effective control of MCs, the possibility of the direct removal of harmful cyanobacteria as well as the removal of dissolved MCs using adsorption strategy was examined. However, to fully utilize the adsorption for the removal of MCs, the application and optimization under actual environmental conditions are still required, thereby meeting the environmental and economic standards. From this study, crucial insights could be provided for the development and selection of effective adsorbent and subsequent adsorption processes for the removal of MCs from water resources.

• Clean Technology
• /
• v.23 no.4
• /
• pp.364-377
• /
• 2017

In this study, to improve the low surface area of domestic anthracite as raw materials of activated carbon, characteristics on chemical activation and VOCs adsorption of activated carbon according to mixing ratio of anthracite and lignite. For these, properties of raw materials, parameter characteristics of preparation processes for activated carbon, and VOCs adsorption characteristic of the prepared activated carbon are analyzed. The experimental results showed that, the domestic anthracite had disadvantages of high contents for ash and lead, arsenic, which were exceeded for the heavy metal limits, in the properties of raw materials. To improve these diadvantages, using the mixing ratio of anthracite and lignite, and the optimum conditions for pretreatment, activation, washing, and pellitization process, the activated carbon had a range of BET (Brunauer-Emmett-Teller) surface area of $1,154{\sim}1,420m^2g^{-1}$ with mesopore development and hydrophobic surface property. The carbons were satisfied with the quality standard for granular activated carbon, and had similar physicochemical properties with the commercial activated carbon. The minimum mixing condition for commercial VOCs activated carbon performance must have the caloric value of above $5,640kcal\;kg^{-1}$, and the carbon had higher adsorption capacity with order of xylene > toluene > benzene according to more higher molcular weight and hydrophobic property.

• Applied Chemistry for Engineering
• /
• v.32 no.6
• /
• pp.671-678
• /
• 2021

Effects of nitric acid treatment of an activated carbon and impregnation of metal chlorides on the activated carbon were investigated to improve ammonia adsorption performance. It was confirmed that functional groups such as hydroxyl and carboxyl groups were introduced onto a surface of the activated carbon with nitric acid treatment. Then, each metal chloride (NiCl₂, MgCl₂, CuCl₂, MnCl₂ or CoCl₂) was impregnated onto the surface-modified activated carbon using an ultrasonic impregnation method. The physicochemical properties and ammonia adsorption performance of various impregnated activated carbons were observed. Metal chlorides were well dispersed by sonication and evenly distributed on the surface of the activated carbon. Despite the reduced specific surface area and pore volume, the surface-modified activated carbon impregnated with metal chlorides exhibited excellent ammonia adsorption performance. In particular, HNO₃-NiCl₂ AC prepared by impregnating NiCl₂ showed the best ammonia adsorption capacity of 3.736 mmol·g^-1, which was improved by about 57 times compared to that of an untreated activated carbon (0.066 mmol·g^-1).

• Journal of Korean Society of Environmental Engineers
• /
• v.37 no.3
• /
• pp.175-181
• /
• 2015

Activated carbon impregnated with polyethyleneimine (PEI) was evaluated as a functionalized adsorbent for $CO_2$ capture. The $CO_2$ adsorption characteristics of the adsorbents was undertaken using GC/TCD, BET surface area and FT-IR. A series of adsorbents were synthesized by impregnating 10, 30, 50 wt% of PEI on activated carbons and were investigated $CO_2$ adsorption capacity at high and low adsorption temperature. The $CO_2$ adsorption capacity at $20^{\circ}C$ and $100^{\circ}C$ was as follow: AC > PEI(10)-AC > PEI(30)-AC > PEI(50)-AC at $20^{\circ}C$ and PEI(10)-AC > PEI(30)-AC > PEI(50)-AC > AC at $100^{\circ}C$. Adsorption capacities of amine functionalized AC was lager than virgin AC at high temperature due to chemisorption by amino-group content. From the results, the PEI(10)-AC showed one of the most promising adsorbents for $CO_2$ capture from flue gas at high temperature.

• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.2
• /
• pp.189-198
• /
• 2009

Tastes and odor in water caused by geosmin and 2-MIB are the major customer complaints for water utilities. Therefore, control of geosmin and 2-MIB is a worldwide concern. In this study, the effects of biofilter media type (three different activated carbons and anthracite), empty bed contact time (EBCT) and temperature on the removal of geosmin and 2-MIB in BAC filters were investigated. Experiments were conducted at three different water temperatures (5, 15 and $25^{\circ}C$) and four different EBCTs (5, 10, 15, and 20 min). The experimental results indicated that the coal based BAC retained more bacterial biomass on the surface of the activated carbon than the other BACs, and increasing EBCT or increasing water temperature also increased the geosmin and 2-MIB removal in BAC filters. To achieve above 50% of removal efficiency for geosmin and 2-MIB in a BAC filter, above 10 min EBCT at $5^{\circ}C$ and 5 min EBCT at above $15^{\circ}C$ were required. The kinetic analysis for the biodegradation of geosmin and 2-MIB indicated a first-order reaction rate at various water temperatures. Data obtained from the BAC filters at various temperatures were also used to evaluate pseudo first-order rate constants for geosmin and 2-MIB. The half-lives evaluated at 5, 15, and $25^{\circ}C$ for geosmin and 2-MIB ranged from 2.39 to 10.31 min and 3.35 to 13.97 min, respectively, which can be used to assist water utilities in designing and operating BAC system.

• Journal of Korean Society of Water and Wastewater
• /
• v.34 no.6
• /
• pp.425-435
• /
• 2020

Numerous chemical modifications on activated carbon such as acidic conditioning, thermal treatment and metal impregnation have been investigated to enhance adsorption capacities of micropollutants in water treatment plants. In this study, chemical modification including acidic, alkaline treatment, and iron-impregnation was evaluated for adsorption of 2,4-dichlorophenol (2,4-DCP). For Fe-impregnation, three concentrations of ferric chloride solutions, i.e., 0.2 M, 0.4 M, and 0.8 M, were used and ion-exchange (MIX) of iron and subsequent thermal treatment (MTH) were also applied. Surface properties of the modified carbons were analyzed by active surface area, pore volume, three-dimensional images, and chemical characteristics. The acidic and alkaline treatment changed the pore structures but yielded little improvement of adsorption capacities. As Fe concentrations were increased during impregnation, the active adsorption areas were decreased and the compositional ratios of Fe were increased. Adsorption capacities of modified ACs were evaluated using Langmuir isotherm. The MIX modification was not efficient to enhance 2,4-DCP adsorption and the MES treatment showed increases in adsorption capacities of 2,4-DCP, compared to the original activated carbon. These results implied a possibility of chemical impregnation modification for improvement of adsorption of 2,4-DCP, if a proper modification procedure is sought.

• Journal of Adhesion and Interface
• /
• v.11 no.4
• /
• pp.137-143
• /
• 2010

Glass beads (GBs) were modified via plasma polymerization coatings in order to enhance the adsorption of polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke and activated carbons (ACs) were also utilized for comparative purposes. First, GBs and ACs were subjected to surface modification via plasma polymerization coating of acrylic acid, acrylonitrile, 1,3-diaminopropane, thiophene or dimethylphosphite with a RF plasma (13.56 MHz) generator. Next, their adsorption behavior was evaluated with a home-made 4-port smoking machine by collecting the total particulate matters (TPMs) on a Cambridge filter pad, followed by the separation of PAHs via solid phase extraction and analysis with GC/MS. Finally, the plasma polymerization coatings were analyzed by FT-IR/ATR to elucidate the adsorption mechanism, while the topology of the modified GBs and ACs were studied by FE-SEM.

• Journal of Korean Society of Water and Wastewater
• /
• v.24 no.6
• /
• pp.661-674
• /
• 2010

Bacterial biomass and its activity were measured in two kinds of granular activated carbon (GAC), the experimental and existing biofiltration system in a drinking water plant. The bacterial biomass was around 210 to 250 nmol P/g WW with phospholipid concentration at acclimation of ozonation treatment. The phospholipid biomass shows more or less a declining gradient along filter depth and no clear seasonality in its values. On the other hand, the microbial activity of [$^3H$]-thymidine and [$^{14}C$]-acetate incorporation within cells increased significantly along the filter depth, showing the difference of three fold between the upper and bottom layer. These factors support the different microbial composition or metabolic activity along the depth of GAC column. Turnover rates, the rate of bacterial biomass and production of biofilm, ranged from 0.26 /hr to 0.37 /hr, indicating a highly rapid recovery itself at amature state. In the non-ozonation treatment, the bacterial biomass was lower than in the ozonation and biological activity also declined towards the filter depth. The biomass levels during cessation of ozonation in the existing GAC filters were 68% of the actively ozonated state.

• Korean Chemical Engineering Research
• /
• v.40 no.6
• /
• pp.694-702
• /
• 2002

Activated carbons have been used as adsorbents in various industrial application, such as solvent recovery, gas separation, deodorization, and catalysts. In this study, the effects of residual water on the activated carbon adsorbent surface on the adsorption capacity of $CCl_4$ were investigated. Adsorption behavior in a fixed bed was studied in terms of feed concentration, flow rate, breakthrough curve and adsorption capacity for $CCl_4$. Desorption characteristics of residual water on activated carbon were also studied. The water contents of the activated carbon were varied in the range of 0-20%(w/w) and all experiments were performed at 298.15 K. The adsorption equilibrium data $CCl_4$ on the activated carbon were well expressed by Langmuir isotherm. The adsorption capacity of $CCl_4$ decreased with increasing residual water content. Desorption of residual water in activated carbon decreased expotentially with $CCl_4$ adsorption. The obtained breakthrough curves using LDF(linear driving force) model represented our experimental data.

• Korean Chemical Engineering Research
• /
• v.44 no.6
• /
• pp.669-675
• /
• 2006

Toluene of aromatic compounds, MEK of ketones and IPA of alcohols were extremely used as VOCs (Volatile Organic Compounds) on the getting into step with industrial process. The adsorption characteristics of three component solvent vapors (Toluene-MEK-IPA) on the activated carbonaceous adsorbents such as AC, ACF and AC+ACF were investigated in a stainless steel fixed bed adsorption experimental apparatus in order to identify those carbons for eliminating and recovering solvent vapors from industrial emission sources. The used activated carbonaceous adsorbents were pelletized commercial activated carbon and activated carbon fiber. The breakthrough curves and adsorption capacity have been obtained at atmospheric pressure in a adsorption fixed bed. It has been found that non-polar and larger molecules have been adsorbed better than polar and smaller molecules. Especially, alcohols and ketones were poorly adsorbed due to competitive adsorbability in ternary mixture system. However, it could be overcome by employment of activated carbonaceous adsorbent which have different porosity distribution appropriately.