• Clean Technology
• /
• v.7 no.1
• /
• pp.75-80
• /
• 2001

In this study, hexavalent chromium (Cr(VI)) plating wastewater in strong acidic condition was treated by reduction and alkalization. Ferrous sulfate ($FeSO_4$), known to reduce Cr(VI) to Cr(III) rapidly at acidic pH, was used as a reductant of Cr(VI). The optimum reduction condition of Cr(VI) was observed at iron to chromium dose ratio of 3:1 by mole concentration. The precipitation of Cr(III) as $Cr(OH)_3$, was achieved by the pH adjustment in the limestone aeration bed. The precipitates were removed less than the upper limit of chromium for effluent at pH over 5.0. The continuous removal of Cr(VI) was performed using the process consisting of reduction vessel, limestone aeration bed, and sedimentation tank coupled with metal screen membrane. As pH was maintained around 5.0 in the limestone aeration bed, insoluble chromic hydroxide flocs was formed continuously. Most chromic hydroxide flocs were filtered by the metal screen membrane with 1450 mesh size, and the treated water to meet the upper limits of chromium for effluent (Cr Conc. 0.25~0.90 mg/l) was obtained in 30 minutes. Periodic backwashing decreased the fouling on the membrane rapidly.

• Clean Technology
• /
• v.3 no.2
• /
• pp.74-86
• /
• 1997

Recently the treatment of industrial wastes by membrane processes has drawn much attention due to increasing demands for clean technology. In the process investigated in this study, metal species in the acidic wastes are precipitated as metal hydroxide forms in a neutralization tank, and acid and base solutions are regenerated by water-splitting electrodialysis(WSED) to be reused in the process. Material balances of the processes for treating pickle liquor and mixed wastewater were calculated to explain conceptual design of the process. Experiments for neutralization precipitation with KOH and NaOH for mixed wastewater were carried out to precipitate metal hydroxide and to recover salt solution as supernatant. Also WSED of the salt solutions producing acid and base was tested in 2 or 3 compartment stacks using KCl and NaCl to investigate the effects of stack configurations on the WSED performance.

• Journal of Environmental Science International
• /
• v.6 no.2
• /
• pp.141-152
• /
• 1997

The pilot plant had been made so as to be an association system from the various items managed to have degrees of efficiency and It have been done to consider the experimental result with irradiance period and pH influence of all major things to treatment function of Waste Stabilization Pond. The results are as following. The attained results for continuous & cyclic irradiance 1. 24L.-reactor was prior to 12L.-12D.-reactor on oxygen generation & algal production ability. 2. 24L.-reactor was prior to 12L.-12D.-reactor on nutrients removal efficiency. 3. In 24L.-reactor it maintained 5mg/L∼6mg/L, DO concent enough to a fish's survival. The attained results for pH condition 1. Oxygen generation ^ algal production in pH 4-reactor were higher than those in pH 10-reactor. 2. The acidic condition at pH 4 and alkalic condition at pH 10 did not so much affect an algal growth and nutrients removal. The attained results for whole 1. In view of the results appeared as [(NH3-N)+(NO3-N)] removal efficiency, 89.1%∼93.9% and PO4-P removal efficiency, 34.3%∼83.7% & COD removal efficiency, 88.5%∼93.9%. It is possible to treat the wastewater with starch and pH which have been known as thedifficult problem. 2. At the point of non using methanol to nitrificate NO3-N, the nutrients removal method by using an algal growth is the most economical method in the whole nutrients removal methods. 3. The nutrients removal method by using an algal growth contributes to natural ecosystem. 4. The nutrients removal method by using an algal growth is excellant in the prevention against the eutrophication.

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.3
• /
• pp.487-494
• /
• 2017

Since nitrate nitrogen is quite stable in aqueous solution, considerable skill is required to remove it. Low concentrations of nitrate nitrogen are easily removed, while high concentrations of nitrate nitrogen are difficult to remove. This study is to show that nitrate nitrogen in the form of gaseous nitrogen can be removed by using zinc ball with a diameter of about 3mm and to test the removal characteristics of nitrate nitrogen under various reaction conditions. As a result of this study, the treatment efficiency of nitrate nitrogen by continuous treatment with zinc ball was about 80%. However, there is a problem that the wastewater must be maintained in an acidic atmosphere of about pH 2, and the treated wastewater must be neutralized and discharged.

• Journal of Korean Society on Water Environment
• /
• v.22 no.2
• /
• pp.328-332
• /
• 2006

Fe(III)-impregnated activated carbon (Fe-AC) was applied in the treatment of synthetic wastewater containing Cu(II). To investigate the stability of Fe-AC at acidic condition, dissolution of Fe was studied with a variation of solution pH ranging from 2 to 4. Fe-AC was unstable at pH 2, showing a gradual increase of the dissoluted Fe as reaction time increased, while negligible amount of Fe was dissoluted above pH 3. This stability test suggests the applicability of Fe-AC in the treatment of wastewater above pH 3. Adsorption capacity of Cu(II) onto activated carbon (AC) and Fe-AC was investigated in a batch and a column test. In the adsorption kinetics, rapid adsorption of Cu(II) onto AC and Fe-AC was noted at initial reaction time and then reached a near complete equilibrium after 6 hrs. Adsorption trends of Cu(II) onto AC and Fe-AC were similar, showing an increased Cu(II) adsorption at higher pH. Compared with AC, Fe-AC showed a greater Cu(II) adsorption over the entire pH range studied in this research. From the adsorption isotherm obtained with variation of the concentration of Cu(II), the maximum adsorption capacity was identified as 61,700 mg/kg.

• Journal of Korean Society on Water Environment
• /
• v.22 no.1
• /
• pp.116-121
• /
• 2006

Fundamental investigations have been carried out to find the applicability of manganese nodule as an adsorbent of nickel ion with an intention that nickel can be secured in manganese nodule along with the treatment of wastewater. The average content of manganese in nodules which used in the experiments was about 27%. The content of nickel in manganese nodules was observed to increase up to 4 times higher with comparison to its original value after adsorption. When the initial concentration of nickel ion in artificial wastewater was lower than 500 mg/L, its adsorbed amount on manganese nodule was shown to increase continuously. However, no more than about 82 mg/L of nickel was attained at higher initial nickel ion concentration than 500 mg/L. The adsorption of nickel ion was increased with temperature under experimental conditions and as the size of manganese nodule particles became smaller more nickel ion was adsorbed on adsorbent. Regarding the effect of pH, the adsorption of nickel ion was more hindered as the solution became acidic. Adsorption behavior of nickel ion on manganese nodule was found to follow the Freundlich model well and kinetic analysis showed that the adsorption reaction of nickel ion was second order. Thermodynamic parameters for the nickel ion adsorption were estimated on the basis of thermodynamic equations and they were in good agreement with experimental results.

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.2
• /
• pp.217-224
• /
• 2017

This is a study on the removal of nitrate nitrogen from wastewater by oxidation and reduction reaction of zinc in an acidic atmosphere. The optimum removal rate of nitrate nitrogen and the optimum pH were studied by controlling the amount of zinc and sulfamic acid. The oxidation efficiency was higher at pH 2.0 in the range of pH 2.0 ~ 4.0 because the reaction occurred more strongly in strong acidic atmosphere. It is advantageous to reduce the nitrate ion to the final nitrogen gas by adding the sulfamic acid to the sulfurous acid because it consumes less $H^+$ ion than when the sulfamic acid is not present. According to the same amount of zinc, nitrate nitrogen was removed by 46.0% while sulfamic acid was not added, whereas nitrite nitrogen was removed by 93.0% by adding sulfamic acid. In addition, In this experiment, zinc was prepared in powder form and its reactivity was larger than that of other common zinc metal, so the removal efficiency was very high, about 80.0%, within one minute after the reaction.

• Korean Journal of Environmental Biology
• /
• v.32 no.4
• /
• pp.271-285
• /
• 2014

Aluminum flows into the river from the abandoned mine leachate, industrial wastewater, and sewage and is responsible for acute toxicity in aquatic organisms. Recently, the number of reports have indicated the increased toxicity in a variety of aquatic organisms' due to the aluminum toxicity. In this study, we reviewed the toxicity of aluminum on aquatic invertebrates, fishes and amphibians and suggested the guideline for management of aluminum residues in aquatic environment and strategies for aluminum toxicity evaluation. In aquatic animals aluminum complexes evoke gill dysfunction primarily, the cytotoxicity, genotoxicity, oxidative stress, disruption of endocrine function, reproductive success, metabolism and homeostasis. Notably, at environmentally relevant concentration, aluminum complex can alter the hormone levels in fish in acidic condition. Further, since the solubility of aluminum is higher in the acidic and basic conditions, thus it is likely that the toxic effects of aluminum may not only occur in acidic water near the abandoned mines but also in lakes and rivers, where pH is raised by algal bloom.

• Journal of Korean Society on Water Environment
• /
• v.23 no.3
• /
• pp.371-376
• /
• 2007

The features of precipitating reaction of fluorine have been examined under several aquatic conditions by employing calcium ion as a precipitant. Based on MINTEQ program, fluorine was found to exist in the forms of $H_2F_2$ and HF in strong acidic environment and change into $F^-$ with increasing pH. In the experimental condition, the precipitating reaction of fluorine progressed rapidly within a few minutes after the reaction started and reached its equilibrium in 10 minutes. As the addition of precipitant was increased, removal of fluorine by the formation of precipitate was promoted and its was also enhanced by the rise of pH. The precipitating reaction of fluorine was impeded when its initial concentration was low and X-ray analysis showed that the crystalline structure of precipitate was mainly $CaF_2$ with partly NaF. Coexisting phosphate in solution influenced the fluorine removal by impeding the precipitate formation and similar effect was found when metallic ion such as $Zn^{2+}$ was present with fluorine.

• Carbon letters
• /
• v.11 no.3
• /
• pp.169-175
• /
• 2010

The study describes the results of batch experiments on the removal of Reactive Yellow 15 (RY15) and Reactive Black 5 (RB5) from synthetic textile wastewater onto Activated Carbon from Walnut shell (ACW). The experimental data were analyzed by the Langmuir, Freundlish, Temkin and Dubinin-Radushkevich (D-R) models of adsorption. The experiments were carried out as function of initial concentrations, pH, temperature (303-333), adsorbent dose and kinetics. The surface area and pore volumes of adsorbent were measured by BET and BJH methods. The findings confirm the surface area (BET) is 248.99 $m^2/g$. The data fitted well with the Temkin and D-R isotherms for RY15 and RB5, respectively. The most favorable adsorption occurred in acidic pH. Pseudo-second order kinetic model were best in agreement with adsorption of RY15 and RB5 on ACW. The results indicate that walnut shell could be an alternative to more costly adsorbent currently being used for dyes removal.