• YAKHAK HOEJI
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• 제37권1호
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• pp.66-75
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• 1993

Dental abrasive, dicalcium phosphate dehydrate (DCPD) was prepared and the several important factors affecting on the quality of toothpaste were investigated by means of set test, glycerine absorption, Coulter counter test, color difference, BET adsorption, mercury porosimetery, and rheogram comparing with two foreign DCPDs, MFO4 and Dentphos K. Sample DCPD was prepared by reaction between 85% H$_{3}$PO$_{4}$ and 15% milk of lime at $39^{\circ}C$ (pH6.5), and stabilized with TSPP and TMP. The physicochemical properties of Sample DCPD were obtained as follows: whiteness (98.99), average particle size (15.5 $\mu\textrm{m}$), pH (7.9), remainder particle weight (0.49w/w%), glycerine absorption value (64 ml), and set test (passed). N$_{2}$ adsorption curves (BET) of three kinds of DCPD showed non-porous type III isotherm. BET adsorption parameters of sample DCPD showed that surface area was 24.9 m$^{2}$/g, total pore volume 0.09 cm$^{3}$/g and average pore radius 72.0 $\AA$. The rheogram of the toothpaste containing each DCPD showed bulged plastic flow with yield vlaue and thixotropic behavior. These results meet standard requirements as abrasive standard, and suggested that synthesized sample DCPD could be used a dental abrasive such as a high quality grade in practice as foreign DCPDs.

• Journal of the Korean Society of Marine Environment & Safety
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• 제24권2호
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• pp.196-202
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• 2018

In this study, we investigated phosphate removal efficiency according to pretreatment (pyrolysis temperature, pyrolysis time, particle size) of oyster shells as a basic study for their recycling. And XAFS analysis and isothermal adsorption experiments were performed to investigate the phosphate removal characteristics of oyster shells. As a result, the removal efficiency was good at $600^{\circ}C$ pyrolysis temperature with 6 hour pyrolysis time and 0.355 ~ 0.075 mm particle size. Isothermal adsorption experiments showed that the Langmuir model is suitable for adsorption of oyster shells. XAFS analysis showed that calcium phosphate formed on the oyster shell pyrolyzed at $600^{\circ}C$. In other words, it was confirmed that the formation of calcium phosphate by the calcium ion elution of the oyster shell contributes to the decrease of phosphate concentration.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 한국지하수토양환경학회 1999년도 정기총회 및 춘계 공동 학술발표회
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• pp.100-101
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• 1999

• Journal of Korean Society of Water and Wastewater
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• 제26권6호
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• pp.841-849
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• 2012

The effluent quality of phosphorus is strengthened by the national standard to conserve water resources to lessen the eutrophication threat. The soluble phosphate in the wastewater effluent can be removed using the converter slag as solid waste produced through the steel making process. The experiments for removal efficiencies and removal constants were performed for this research with the artificial wastewater following several different conditions, particle size, phosphate concentration and initial pH. The correlation coefficients of Freundlich adsorption isothem were 0.9505 for $PS_A$, 0.9183 for $PS_B$, respectively. The removal efficiency was 87-94 % for $PS_A$ and 90-96 % for $PS_B$ respectively. The pH of the wastewater was elevated to pH 11.8 for the initial pH 8.5, phosphate removal efficiency was the highest as 84 % ~ 98 %. In case of 10 mg/L of the intial phosphate, the removal efficiency was 96 ~ 98 %. The more initial pH increases, the higher the reaction rate constant is.

• Journal of Korean Society on Water Environment
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• 제20권5호
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• pp.466-472
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• 2004

Red mud is formed as a waste during bauxite refining known as Bayer's process. Its main constituents are iron, aluminium, sodium and silica. The disposal of large quantities of wasted red mud causes a serious ecological problem. In this study, the red mud wasted from the bauxite refinery was studied for phosphate removal from aqueous solution according to activation methods. The influence of heat treatment, and neutralization with sea water and acid treatment level for the optimum conditions for phosphate removal have been determined. Heat treatment combined with acid treatment is most suitable for the removal of phosphate from aqueous solution. The optimal condition was activated with 1 N HCl solution after heating in $600^{\circ}C$ during 4 hours. Acid and heat treatment causes sodalite compounds which hinder the phosphate adsorption to leach out. The adsorption data obtained followed a first-order rate expression and fitted well with the Freundlich Isotherm well.

• Membrane and Water Treatment
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• 제9권2호
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• pp.95-104
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• 2018

Copper pollution around the world has caused serious public health problems recently. The heavy metal adsorption on traditional membranes from wastewater is limited by material properties. Different adsorptive materials are embedded in the membrane matrix and act as the adsorbent for the heavy metal. The carbonized leaf powder has been proven as an effective adsorbent material in removing aqueous Cu(II) because of its relative high specific surface area and inherent beneficial groups such as amine, carboxyl and phosphate after carbonization process. Factors affecting the adsorption of Cu(II) include: adsorbent dosage, initial Cu(II) concentration, solution pH, temperature and duration. The kinetics data fit well with the pseudo-first order kinetics and the pseudo-second order kinetics model. The thermodynamic behavior reveals the endothermic and spontaneous nature of the adsorption. The adsorption isotherm curve fits Sips model well, and the adsorption capacity was determined at 61.77 mg/g. Based on D-R model, the adsorption was predominated by the form of physical adsorption under lower temperatures, while the increased temperature motivated the form of chemical adsorption such as ion-exchange reaction. According to the analysis towards the mechanism, the chemical adsorption process occurs mainly among amine, carbonate, phosphate and copper ions or other surface adsorption. This hypothesis is confirmed by FT-IR test and XRD spectra as well as the predicted parameters calculated based on D-R model.

• Korean Journal of Environmental Agriculture
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• 제27권3호
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• pp.231-238
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• 2008

This study proposed the method of phosphate recovery from municipal wastewater by using ferrous iron waste, generated from the mechanical process in the steel industry. In the analysis of XRD, ferrous iron waste was composed of $Fe_3O_4$ (magnetite), practically with $Fe^{2+}$ and $Fe^{3+}$. It had inverse spinel structure. In order to identify the adsorption characteristic of phosphate on ferrous iron waste, isotherm adsorption test was designed. Experimental results were well analyzed by Freundlich and Langmuir isotherm theories. Empirical constants of all isotherms applied increased with alkalinity in the samples, ranging from 1.2 to 235 $CaCO_3/L$. In the regeneration test, empirical constants of Langmuir isotherm, i.e., $q_{max}$ (maximum adsorption capacity) and b (energy of adsorption) decreased as the frequency of regeneration was increased. Experiment was further performed to evaluate the performance of the treatment scheme of chemical precipitation by ferrous iron waste followed by biological aerated filter (BAF). The overall removal efficiency in the system increased up to 80% and 90% for total phosphate (TP) and soluble phosphate (SP), respectively, and the corresponding effluent concentrations were detected below 2 mg/L and 1 mg/L for TP and SP, respectively. However, short-circuit problem was still unsolved operational consideration in this system. The practical concept applied in this study will give potential benefits in achieving environmentally sound wastewater treatment as well as environmentally compatible waste disposal in terms of closed substance cycle waste management.

• Journal of Korean Society of Environmental Engineers
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• 제28권6호
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• pp.583-587
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• 2006

In this study, the phosphate adsorption characteristics of zirconium mesostructures synthesized under different conditions were estimated. X-ray diffraction analysis, phosphate adsorption isotherm test and kinetic test was performed for the zirconium mesostructures synthesized at different inorganic/surfactant molar ratio and with different surfactant templates. The test results were analyzed with adsorption models. From this work, it was found that at the inorganic/surfactant molar ratio of 1/0.50($0.013{\cdot}Zr(SO_4){_2}:0.068{\cdot}surfactant:5.55{\cdot}H_2O$), the meso-pores in the material could be most uniformly and clearly formed and thus the adsorption capacity and reaction rate of material could be maximized. And the pore size in the mesostructure increased with the chain length of surfactant template used, and maximum phosphate adsorption amount and reaction rate could be achieved with the zirconium mesostructure synthesized with the surfactant template of dodecyltrimethylammonium bromide.

• Korean Journal of Soil Science and Fertilizer
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• 제49권5호
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• pp.429-433
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• 2016

Adsorption and precipitation of cadmium (Cd) could be dependent on rate of P addition and Cd level in soil. Therefore, the objective of this study was to examine how addition rate of P affect mechanisms of Cd immobilization such as adsorption and precipitation in different levels of Cd in soil. Arable soils were spiked with inorganic Cd ($CdCl_2$) to give a total Cd concentration of 10, 100, and $1,000mg\;Cd\;kg^{-1}$. Monopotassium phosphate ($KH_2PO_4$, MPP) was selected as phosphate material and mixed with the pretreated arable soil at the rates of 0, 800, 1,600 and $3,200mg\;P\;kg^{-1}$. The mixture soils were incubated at $25^{\circ}C$ for 8 weeks in dark condition. Soil pH decreased with increasing MPP addition rate in all levels of Cd but negative charge of soil increased, thereby reducing 1 M $NH_4OAc$ extractable Cd. Soil solutions were undersaturated with respect to $CdCO_3$ and $Cd_3(PO_4)_2$ with all P addition rate in soil with low Cd level (${\leq}100mg\;Cd\;kg^{-1}$) but supersaturated in soil with high Cd level ($1,000mg\;Cd\;kg^{-1}$). From the above results, Cd solubility was controlled by precipitation of Cd minerals such as $CdCO_3$ and $Cd_3(PO_4)_2$ in soil with high Cd level but by Cd adsorption induced by increase in negative charge of soil with low level of Cd.

• Journal of the Mineralogical Society of Korea
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• 제22권4호
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• pp.289-295
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• 2009

The characteristics of phosphate desorption on kaolinite was studied by batch adsorptiondesorption experiments. Desorption procedure was carried out through sequential extraction method at pH 4. The phosphorous contents were measured using UV-VIS-IR spectrophotometer with 820 nm wavelength. The adsorption-desorption reaction of P on kaolinite was irreversible, and most of adsorbed P on kaolinite were not easily dissolved to aqueous solution, but may might be fixed on kaolinite surface. The desorption isotherms were well fitted with the Freundlich and Temkin equations in the case of short reaction and long reaction time, respectively. The desorption reaction was divided into the early fast reaction and the later slow reaction. The percentage of desorption generally decreased with increasing adsorbed P concentration and increasing desorption reaction time.