This study was performed to investigate the feasibility of ion-exchange resins as soil amendment. To select resins, weinvestigate four kinds of ion exchange resins, which ions have the most adsorption efficiency of ions (N+, PO4−, K+). Inthe Cation (H+) vs Anion (OH−)=1:2 (w:w), it showed that the highest N, P, K adsorption efficiency was about 80%and reached pH 6~7 & EC 1~2dS/m after 20min. The ability to maintain ion adsorption, it was investigated that thegentle curve of the residual ion ratio of nitrate nitrogen, available phosphorus, exchangeable potassium was maintained.On the other hand, the control (Slow release fertilizer) was significantly reduced under artificial rainfall conditions. Inaddition, the results of three consecutive crop test were showed that the growth of crops decreased 41.8% than the earlygrowth in the control group, whereas decreased 8.3% in the treatment group (ion exchange resins). According to the resultsof soil analysis, it was reduced that the fertilizer ingredients (N 94%, P 74.5%, K 98.6%) in the control and reducedfertilizer ingredients (N 64%, P 60.3%, K 58.4%) in the treatment. Overall, it was estimated that the Ion-exchange resinscould be used as a soil amendment.

The effects of the cation-to-anion resin ratio and bed depth on ion exchange performance of mixed-bed were studied at ultralow solution concentration. Breakthrough curves were experimentally obtained for NaCl solution as functions of resin ratio and bed depth. The bed depth affects the pattern of the sodium breakthrough curve but not the chloride breakthrough curve in beds because of the selectivity difference. Resin selectivity determines the shape of breakthrough curves. Some sodium and chloride breakthrough curves crossed at a point as a function of resin ratio. The lower cation-to-anion resin ratio showed the higher effluent concentration or treated volume of the crossover point regardless of the total resin weight.

Lab-scale Electrodialysis(ED) system with different membranes combined with before or after pyroma process were carried out to remove nitrate from two pickling acid wastewater containing high concentrations of NO3-(≈150,000 mg/L) and F-(≈160,000 mg/L) and some heavy metals(Fe, Ti, and Cr). The ED system before Pyroma process(Sample A) was not successful in NO3- removal due to cation membrane fouling by the heavy metals, whereas, in the ED system after Pyroma process(Sample B), about 98% of nitrate was removed because of relatively low NO3- concentration (about 30,000 mg/L) and no heavy metals. Mono-selective membranes(CIMS/ACS) in ED system have no selectivity for nitrate compared to divalent-selective membranes(CMX/AMX). The operation time for nitrate removal time decreased with increasing the applied voltage from 10V to 15V with no difference in the nitrate removal rate between both voltages. Nitrate adsorption of a strong-base anion exchange resin of Cl- type was also conducted. The Freundlich model(R2 > 0.996) was fitted better than Langmuir model(R2 > 0.984) to the adsorption data. The maximum adsorption capacity (Q0) was 492 mg/g for Sample A and 111 mg/g for Sample B due to the difference in initial nitrate concentrations between the two wastewater samples. In the regeneration of ion exchange resins, the nitrate removal rate in the pickling acid wastewater decreased as the adsorption step was repeated because certain amount of adsorbed NO3- remained in the resins in spite of several desorption steps for regeneration. In conclusion, the optimum system configuration to treat pickling acid wastewater from stainless-steel industry is the multi-processes of the Pyroma-Electrodialysis-Ion exchange.

Ion exchange resin was used to remove silica ion at ultralow concentration. The effects of temperature, type of ion exchange resin and single/mixed-resin systems on removal efficiency were estimated. As temperature increased, the slope of concentration profile became stiff, and the equilibrium concentration was higher. In the single resin system, the removal of silica was continued up to 400 min, but the silica concentration was recovered to initial concentration after 400 min due to the effect of dissolved CO2. In the mixed-resin system it took about 600 min to reach equilibrium. Because of faster cation exchange reaction than anion exchange reaction, the effect of CO2 could be removed. Based on the experimental results carried out in the mixed-resin system, the selectivity coefficients of silica ion for each ion exchange resin were calculated at some specific temperatures. The temperature dependency of the selectivity coefficient was expressed by the equation of Kraus-Raridon type.

This study introduces the development of new supercritical water oxidation(SCW)(multiple step oxidation) to destruct recalcitrant organic substances totally and safely by using sodium nitrate as an oxidant. This method has solved the problems of conventional SCW, such as precipitation of salt due to lowered permittivity, pressure increase following rapid rise of reaction temperature, and corrosion of reactor due to the generation of strong acid. Destruction condition and rate in the supercritical water were examined using Polyvinyl Chloride(PVC) and ion exchange resins as organic substances. The experiment was carried out at 450℃ for 30 min, which is relatively lower than the temperature for supercritical water oxidation (600-650℃). The decomposition rates of various incombustible organic substances were very high [PVC(87.5%), Anion exchange resin(98.6%), Cationexchange resin(98.0%)]. It was observed that hetero atoms existed in organic compounds and chlorine was neutralized by sodium (salt formation). However, relatively large amount of sodium nitrate (4 equivalent) was required to raise the decomposition ratio. For complete oxidation of PCB was intended, the amount of oxidizer was an important parameter.

The effects of long-term fertilization on soil properties and nutrient availability are not well documented for cassava cultivation in Vietnam. In 1990, a field research plots were established with 12 treatments to test the effect of different rates of nitrogen (N), phosphorus (P) and potassium (K) on soil properties in Acrisols at Thai Nguyen University in Northern Vietnam. In 1999, composite soil samples (0 to 20cm depth) were collected from eight selected plots for measurements of nutrient supply rates by ion exchange membrane probes and for growing corn and canola in a growth chamber with and without added lime. Generally, long-term nitrogen (N) fertilization increased available N supply rates but decreased available potassium (K) and magnesium (Mg). Long-term phosphorus(P) applications increased canola N, calcium (Ca) and Mg uptake. Canola P uptake increased with increased P rates only when lime was added. Long-term K applications increased canola N, K, Ca, Mg uptake but only significantly increased corn N uptake. Liming significantly increased uptake of N, P, K, Ca, Mg and S for both corn and canola. However, N H4- N, K and Mg soil supply rates were reduced when lime was added, due to competition between Ca from the added lime and other nutrients.

A kinetic study for anion exchange was performed for commercially available Cl- type anion exchange resin in use to remove nitrate in water. The obtained results from the batch reactor were applied to the Langmuir and Freundlich models. The constants for Langmuir model were qmax=29.82 and b=0.202, and for Freundlich model were K=5.509 and n=1.772. Langmuir model showed better fit than Frendlich model for the experimental results. Ion exchange reaction rate was also calculated and the approximate first-order reaction, rate constant k1 was 0.16 L/㎎·hr. Effective diffusion coefficient was obtained in the range from 9.67×10 exp (-8) to 1.67×10 exp (-6) ㎠/sec for initial concentration change, and from 6.09×10 exp (-7) to 3.98×10 exp (-6) ㎠/sec for reaction temperature change. Activation energy during the diffusion was calculated as 36 ㎉/㏖.

Ion exchange performance to remove nitrate in water was studied using commercially available strong base anion exchange resin of Cl^- type in the batch and continuous column reactors. The performance was tested using the effluent concentration histories for continuous column or equilibrium concentrations for batch reactor as a function of time until resins were exhausted or reached ionic equilibrium between resin and solution. Anion exchange resin used in this study was more effective than activated carbon or zeolite for nitrate removal. With large resin amount or low initial concentration, nitrate removal characteristics for a typical gel-type resin was increased. On considering the relation between the breakthrough capacity and nitrate concentration of the influent, the use of anion exchange resin were suitable for the higher order water treatment. The nitrate removal of above 90% could be possible until the effluent of above 650 BV was passed to the column. Thus, the commercially available strong base anion exchange resin of Cl^- type used in this study could be effectively used as economic material for treatment of the groundwater. The breakthrough curves showed the sequence of resin selectivity as SO_4^2- > NO_3, > NO^2- > HCO_3^-. The results of this study could be scaled up and used as a design tool for the water purification system of the real groundwater and surface water treatment processes.

The removal effectiveness of various heavy metal ions in boron-rich containing plants has been studied by means of spectroscopic and pH methods. Treatment of the boron-rich containing sample which was collected from cherry and root of cabbage to heavy metal ions is resulted in that an excellent removal effect shows in the case of large ionic size of heavy metal. Stability constants are depended on the variation of pH.