• Journal of Environmental Health Sciences
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• v.21 no.4
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• pp.17-23
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• 1995

As a basic experiment to develope biological pretreatment proces~ in water treatment, the experiments on biodegradability and isothermal adsorption of activated carbon were performed on refractories such as humic acid, $NH_3-N$, phenol and ABS which caused the problems in drinking water treatment. Also, the treatabilities on humic acid were examined in the continuous flow type reactors. The removal efficiencies of humic acid, $NH_3-N$, phenol and ABS in the biodegradable experiments for 5 days were 20.1%, 73.4%, 91.7% and 97.5%, respectively. In the isothermal adsorption test of refractories on activated carbon to be used as a media in the continuous flow type reactors, ABS and phenol are adsorbed easily, but humic acid and $NH_3-N$ are difficult to be done. The removal efficiencies of humic acid in granular activated carbon(GAC) reactor were about 7-8% higher than in biological activated carbon(BAC) reactor. The removal efficiencies of humic acid in biological fluidized bed(BFB) reactor were about 30% in GAC media, but were almost zero in sea sand media.

• Environmental Analysis Health and Toxicology
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• v.13 no.1_2
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• pp.11-17
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• 1998

Cadmium, a major aquatic pollutant in many parts of the world, is toxic and readily accumulated in aquatic organisms. It mainly exists in water as complexes with organic ligands such as dissolved organic carbon and this complexation is known to have effects on the aquatic toxicities. In this study, acute toxicity, histology, and bioaccumulation were studied to evaluate effects of humic acid on cadmium toxicity and bioavailability to fish using Oryzias lalipes and Cyprinus carpio. 96h-LC$_{50}$ of cadmium was 6.38mg/L using Oryzias latipes. However, the mortality showed the dose-dependent decrease when humic acid was added to the test solution. When fish were exposed to 5 mg/L of cadmium, histological changes in the exposed organs (caudal fins, gills, kidney, liver, and gut) of C~lprinus carpio were decreased by humic acid, especially in kidney and liver. Bioaccumulation of cadmium also decreased by treatment of humic acid. It seems that the formation of complexes between cadmium and humic acid may decrease bioavailability of cadmium to fish, and thus reduce the toxic effects of cadmium.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.2
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• pp.114-122
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• 1995

Complexation experiment between humic acid and heavy metal cations was conducted to clear information on heavy metal adsorption by soil organic constituent. The absorbance of UV-visible light of humic acid-metal complexes increased with increasing wavelength, and the order of their absorbance was in the order of Zn->Cd->Cu- saturated humic acid. Carboxyl and phenolic OH groups participated in the complex formation between heavy metal cations and functional groups of humic acid, and the amounts complex was in the order of $Cu^{+{+}}$ > $Zn^{+{+}}$ $\geq$ $Cd^{+{+}}$. The stability constants of humic acid-metal complexes increased with increasing pH, and the order of first stability constants was $Zn^{+{+}}$ > $Cd^{+{+}}$ > $Cu^{+{+}}$, and those of second and overall stability constants were $Cu^{+{+}}$ > $Zn^{+{+}}$ > $Cd^{+{+}}$. With increasing pH, the average binding numbers betwen heavy metal cations and functional groups of humic acid increased the order of $Cu^{+{+}}$ > $Zn^{+{+}}$ > $Cd^{+{+}}$. It was postulated that two types of complexations between heavy metal cations and functional groups of humic acid. One was the reactions in which only carboxyl groups participated to form complexes, and the other was those in which both carboxyl and phenolic OH groups simultaneously participated.

• Journal of Korean Society on Water Environment
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• v.20 no.5
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• pp.520-524
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• 2004

As a feasibility study for the application of carbon nanotubes to the treatment of environmental pollutants, the adsorption characteristics of humic acid on carbon nanotubes has been investigated. The dispersion features of carbon nanotubes in aquatic environment were investigated by measuring the variation of their electrokinetic potentials with pH, and the effects of some dispersants on their dispersion features were also examined. Under the experimental conditions, humic acid was observed to mostly adsorb on nanotubes within a few minutes and reach the equilibrium state within about one hour. The adsorption features of humic acid on nanotubes were found to follow the Freundlich model better than the Langmuir Model. Humic acid adsorbed on carbon nanotubes endothermically and the change of enthalpy in adsorption reaction was estimated to be ca. 18.37kJ/mol at standard state. The entropic change in adsorption reaction for humic acid was ca. 0.0503kJ/mol at standard state and the activation energy for adsorption was also estimated based on the change of rate constants with temperature. FT-IR investigations showed that the functional groups such as alcohol, ester, and aromatics existing in the chemical structure of humic acid might work as the bridge in its adsorption on nanotubes.

• Bulletin of the Korean Chemical Society
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• v.14 no.6
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• pp.726-732
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• 1993

A comparative study on cadmium(II) complexation with three well characterized humic acids (SHA: soil humic acid from the Okchun Metamorphic Belt; AqHA: aquatic humic acid from Gorleben underground aquifer, Germany; CoHA: commercially available humic acid from the Aldrich Co.) was carried out in 0.1 M $NaClO_4$ at different solution pH(5.0, 5.5, and 6.0) using the ultrafiltration technique. The maximum binding ability (MBA) of the humic acids for cadmium(II) was observed to vary with their origins and solution pH. The results suggest that 1 : 1 complex predominates within the experimental range, and the conditional stability constants were calculated based on the assumption of cooperative binding, yielding log K values that were quite similar (CoHA: 4.17${\pm}$0.08; AqHA: 4.14${\pm}$0.07; SHA: $4.06{\pm} 0.12\;l\;mol^{-1}$ at pH 6.0) irrespective of humic acid origins or pH. By contrast a nonlinear Schatchard plot was obtained, using the cadmium(II) ion selective electrode speciation analysis method, which indicated that humic acid may have two or more classes of binding sites, with $log\;K_1\;and\;log\;K_2$ of 4.73${\pm}$ 0.08 and $3.31{\pm}0.14\;l\;mol^{-1}$ respectively.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.2 no.2
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• pp.139-148
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• 1998

The charge densities of humic acid and humic extract have been determined by back titration using spectrophotometry as the method of end point detection and several cationic polymers of different charge density(copolymers of acylamide and dimethylaminoethylacrylate and polydiallyidimethylammonium chloride, PDDA), and a cationic indicator o-toluidine blue(o-Tb). The charge densities of humic acid and humic extract obtained depend on the charge densities of cationic polymers used. When the polymers of lower charge density are used, lower apparent charge density values are obtained, but for polymers of high charge density(above 2.5 meq/g), the measured values are almost identical, but also are nearly the same as that obtained for PDDA which has a high charge density(about 6 meq/g). For polymers of lower charge density, it is considered that the optimum dosage does not correspond to 1 :1 charge neutralization between anionic and cationic groups. Polymers of high charge density should be used in order to achieve a complete charge neutralization. As humic acid and humic extract are dissociable acids, their ionization is heavily pH dependent and so higher charge density values are obtaines with increasing pH.

• Korean Journal of Environmental Agriculture
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• v.17 no.3
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• pp.239-245
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• 1998

To investigate the formation of bound residue with soil organic materials by oxidative coupling, nitroaromatics and their reduced metabolites, the insecticide parathion and the herbicide asulam were incubated with oxidoreductase, laccase or horseradish peroxidase, in the presence or absence of humic monomers. Most of aminotoluenes and amino-nitrophenols were completely transformed while most of nitrotoluenes and nitrophenols remained unchanged by a lactase or horseradish peroxidase in the presence or absence of humic monomers. Amino-nitrotoluenes were not transformed without humic monomers, but the addition of various humic monomers caused a considerable difference in the transformation of amino-nitrotoluenes by a lactase or horseradish peroxidase. Amino-nitrotoluenes were most transformed in the presence of catechol, syringaldehyde and protocatechuic acid. The insecticide parathion with nitro group and its metabolite were not mostly transformed in the presence or absence of humic monomers. The herbicide asulam with amino group remained unchanged without humic monomers as well, but the stimulating effect on the transformation of asulam was caused by the addition of catechol, syringaldehyde, protocatechuic acid or caffeic acid with a lactase.

• Journal of the Korean Chemical Society
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• v.12 no.4
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• pp.155-159
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• 1968

On the extraction of humic acid from peat, the optimum conditions were studied and the effects of them on the characteristics of humic acid were also examined by means of infrared spectroscopy. 1. Pretreatment of peat with diluted 6-8% HCl solution for 5 hrs. prior to extraction with alcohol-benzol azeotropic mixture have resulted the better yield of humic acid. The water soluble Na-humates were obtained by the subsequent extraction with one hundred times quantity of caustic soda solutieon for 1hr. at 90 $^{\circ}C$. Thus the pure humic acids have been yielded approximately 40% (by wt.) from the raw peat. 2. In characteristics of humic acid, the chemical structure, mainly the contents of such functional groups as -COOH, -OH (phenol type), $-CH_2CO-$, $-CH_2{\cdot}O{\cdot}CH_2-$ and aromatic rings were varied according to the concentration of alkaline solution, temperature and time when the humic acids were extracted with alkali.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.243-245
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• 2002

Brackish water desalination using reverse osmosis(RO) membrane is more useful and economic than sea water to solve the shortage of fresh water supply because of its low total dissolved solid(TDS) contents. Silica and humic acid in brackish water make serious fouling problems and cause the decline of permeate flux and increase of operating pressure. In this study, the experiments for removal of silica and humic acid were conducted with calcite particles to prevent membrane fouling and investigated the effect of pH of feed water Adsorption of silica to calcite was higher at pH=7.5 than 9.5 and removal rate was increased according to increase of initial concentration of silica. The effect of pH on adsorption of humic acid was not significant but at low initial concentration the adsorption of humic acid was enhanced at pH 7.5. The result of this study expect to apply to brackish water desalination experiment of flat-sheet reverse osmosis membrane.

• Applied Biological Chemistry
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• v.9
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• pp.153-159
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• 1968

In this paper the auther investigated the chemical properties, process of humification and type of humic acid in soils which were reclaimed by farming for cultivation in Kangwondo. The results obtained in this studies were summarized as follows: 1. General chemical components of these soil were similar to the ordinary soil but C.E.C. and humus contents were found much more 2. Humic acid and fulvic acid which were extracted with NaOH from soil were greater than those of Na-pyrophosphate(Na-p.) and NaF. Hmus contents and PQ% were increased much more in the upper layer than in the lower layer. 3. Degree of humification of humic acid extracted with NaOH. was very similar to those extracted with Na-pyrophosphate. Humification degree of humic acid extracted with NaF was lower than humic acid which were extracted with NaOH and Na-pyrophosphate. But humification degree of humic acid extracted with NaOH was similar to that with Na-pyrophosphate. Humic acid in B soil and the upper layer was higher than A, C soil and the lower layer of soil, in humification degree. 4. Humic acids extracted with NaOH and Na-pyrophosphate from soil were fractionated by Mg into two parts ${\alpha}$ type and ${\beta}$ type humic acid. Humic acids of ${\alpha}$ and ${\beta}$ type extracted with NaOH were higher than these of Na-pyrophosphate in humification degree. In this soil the humification degree of humic acid was not changed during the period of cultivation. 5. ${\alpha}$, ${\beta}$ type humic acid extracted with NaOH were very similar to the humic acid extracted with Na-pyrophosphate in shapes of absorption curves.