The interfacial chemical behavior, lattice exchange and dissolution, of FeS(s) as one of the important sulfide minerals was studied. Emphases were made on the surface characterization of hydrous FeS(s), the lattice exchange of Cu(Ⅱ) and FeS(s), and its effect on the dissolution of FeS(s), and also affect some organic ligands on that of both Cu(Ⅱ) and FeS(s), Cu(Ⅱ) which has lower sulfide solubility in water than FeS(s) undergoes the lattice exchange reaction when Cu(Ⅱ) ion contacts FeS(s) in the aqueous phase. For heavy metals which have higher sulfide solubilities in water than FeS(s), these metal ions were adsorbed on the surface of FeS(s) Such a reaction was interpreted by the solid solution formation theory. Phthalic acid(a weak chelate agent) and EDTA(a strong chelate agent) were used to demonstrate the effect of organic ligands on the lattice exchange reaction between Cu(Ⅱ) and FeS(s). The pHzpc of FeS(s) is 7 and the effect of ionic strength is not showed. It can be expected that phthalic acid has little effect on the lattice exchange reaction between Cu(Ⅱ) and FeS(s), whereas EDTA has very decreased the removal of Cu(Ⅱ) and FeS(s). This study shows that stability of sulfide sediments was predicted by its solubility. The pH control of the alkaline-neutralization process to treat heavy metal in wastewater treatment process did not needed. Thereby, it was regarded as an optimal process which could apply to examine a long term stability of marshland closely in the treatment of heavy metal in wastewater released from a disused mine.

Among various reactions which metal sulfides can undergo in the reducing environment, the lattice exchange reaction was examined in a attempt to selectively remove heavy metal ions contained in the Fe-Coagulants acid solution. We have examined Zeta potential along with pHs to investigate surface characteristics of FeS(s). As a result of this experiment, zero point charge(ZPC) of FeS is pH 7 and zeta potential which resulted from solid solution reaction between Pb(Ⅱ) and FeS(s) is similar to that of PbS(s). Solubility characteristics of FeS(s) is appeared to that dissolved Fe(Ⅱ) concentration increased in less than pH 4, and also increased with increasing heavy metal concentration. Various heavy metal ions(Pb(Ⅱ), Cu(Ⅱ), Zn(Ⅱ)) contained in Fe-coagulants acid solution were removed selectively more than ninety-five percent in the rang of pH 2.5∼10 by FeS(s). From the above experiments, therefore, We could know that the products of reaction between heavy metal ions and FeS(s) are mental sulfide such as PbS(s), CuS(s) and ZnS(s).

This study aimed to elucidate the relationship between theoretical parameters affecting the coagulation process and the real coagulation phenomenon applied to the dye wastewater. Emphasis was placed on the effective removal of the suspend particulates. Parameters studied in this study are pH, coagulant concentration and surface potential. Optimal dosages of coagulants by the measurement of the zeta potential at lower then 25℃ are 5×10-3 M of FeCl3 and 1.4×10-6 M of Fe2(SO4)3. The results were well agreeded with the separate jar-test results. Emphasis was also placed on the relationship between water quality and the content of SS. It was found that the wastewater quality is greatly dependent on the amount of SS. At the condition with the best removal of SS, COD and DOC were reduced to 65 % and 85 %, respectively The turbidity at the above condition was reduced from 300 NTU to 0∼1 NTU. Efforts were made to clarify the behavior of the suspend solid as affecting the water quality. 12,000∼13,000 particles/l0mL in 1∼50㎛ size range particulates in the raw wastewater were reduced to 300 particle/l0mL in the same range after treatment. This research has proposed the methodology to find out the optimal condition of coagulation for small scale wastewater treatment plant or chemical coagulation process.

Surface complexation models(SCMs) have been performed to predict metal ion adsorption behavior onto the mineral surface. Application of SCMs, however, requires a self-consistent approach to determine model parameter values. In this paper, in order to determine the metal ion adsorption parameters for the triple layer model(TLM) version of the SCM, we used the zeta potential data for Zeolite and Kaolinite, and the metal ion adsorption data for Pb(Ⅱ) and Cd(Ⅱ). Fitting parameters determined for the modeling were as follows ; total site concentration, site density, specific surface area, surface acidity constants, etc. Zeta potential as a new approach other than the acidic-alkalimetric titration method was adopted for simulation of adsorption phenomena. Some fitting parameters were determined by the trial and error method. Modeling approach was successful in quantitatively simulating adsorption behavior under various geochemical conditions.

Iron hydroxides are good adsorbents for uncomplexed metals, some metal-ligand complexes and many metal oxyanions. However, their adsorption properties of these precipitations are not fully exploited in wastewater treatment operations because of difficulties associated with their separation from the aqueous phase. This study describes experiments in which iron hydroxides were coated onto the surface of ordinary adsorbents(Sea sand) that are very resistant to acids, The coated adsorbents were used in adsorption of oxyanionic metals. The process was successful in removing some anions such as SeO3(-Ⅱ) over a wide range of metal concentrations and sorption of oxyanionic metals increased with decreasing pH. Formation of two surface complexes for oxyanionic metals adsorption on iron hydroxides comprise (1) complexation of the free anion by a positively charged surface site, and (2) protonation of the adsorbed anion (or alternatively adsorption of a protonated form from solution) The coated adsorbents are inexpensive to prepare and could serve as the basis of a useful oxyanionic metal removal.

Soil properties which affect the retention of Pb(Ⅱ) were investigated in the laboratory. It was determined, through selective removal, that organic matter and Fe-oxides are of lesser importance in influencing Pb retention than are soil clay minerals. The following trend : clays > organic matter > Fe-oxides represents the relative importance of each constituent in the adsorption of Pb by soils. The consistently greater Pb uptake by surface over subsurface samples was apparently due to differences in organic matter content, inasmuch as organic matter removal from both resulted in similar adsorption characteristics. All five soils studied exhibited a pH-dependent trend of adsorption. The extent of Pb adsorption was least at low pH values(4∼5), was maximum in the neutral pH range, and leveled off or diminished under more alkaline conditions. There was no strong correlation between Pb uptake and soil cation exchange capacity as routinely measured by the NH4OAc method. A knowledge of clay mineralogy in conjunction with soil pH is suggested as being the most reliable guide to predicting Pb retention by soils.

The adsorption of Cs-137 and Sr-90 onto kaolinite in prescence of major groundwater cations (Ca2+, K+, Na+) with different concentrations was simulated by using triple-layer surface complexation model (TL-SCM). The site density (8.73 sites/nm2) of kaolinite used for TL-SCM was calculated from it's CEC and specific surface area. TL-SCM modeling results indicate that concentrations dependence on 137Cs and 90Sr adsorption onto kaolinite as a function of pH is best modeled as an outer-sphere surface reaction. This suggests that Cs+ and Sr2+ are adsorbed at the β-layer in kaolinite-water interface where the electrolytes, Nacl, KCl and CaCl2, bind. However, TL-SCM results on Sr adsorption show a discrepancy between batch data and fitting data in alkaline condition. This may be due to precipitation of SrCO3 and complexation such as SrOH+. Intrinsic reaction constants of ions obtained from model fit are as follows: Kintcs=10-2.10, KintSr=10-2.30, KintK=10-2.80, KintCa=10-3.10 and KintNa=10-3.32. The results are in the agreement with competition order among groundwater ions (K+〉Ca2+〉Na+) and sorption reference of nuclides (Cs-137〉Sr-90) at kaolinite-water interface showed in batch test.

In the present paper, batch and semi-continuous settling characteristics of a binary calcium carbonatewater system were investigated. Using experimental data of batch settling characteristics, a graphical analysis for a semi-continuous thickening column was developed and compared with experimental results on the basis of Kynch theory, only where the feed velocity line was within the limits of Kynch theorem Ⅲ. The analysis showed good agreement with experiments. Quite erroneous results, however, was observed for the analysis of a sludge region on the underloaded operation, which was considered due to the deviation from the limits of theory.