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Stabilization of arsenic and lead by magnesium oxide (MgO) in different seawater concentrations
Kameda, Kentaro,Hashimoto, Yohey,Ok, Yong Sik Elsevier 2018 Environmental pollution Vol.233 No.-
<P><B>Abstract</B></P> <P>Ongoing sea level rise will have a major impact on mobility and migration of contaminants by changing a number of natural phenomena that alter geochemistry and hydrology of subsurface environment. In-situ immobilization techniques may be a promising remediation strategy for mitigating contaminant mobility induced by sea level rise. This study investigated the reaction mechanisms of magnesium oxide (MgO) with aqueous Pb and As under freshwater and seawater using XAFS spectroscopy. Initial concentrations of Pb and As in freshwater strongly controlled the characteristics of the reaction product of MgO. Our study revealed that i) the removal of aqueous Pb and As by MgO was increased by the elevation of seawater concentration, and ii) the removal of As was attributed primarily to (inner-sphere) surface adsorption on MgO, independent on seawater concentrations, and iii) the retention mechanism of Pb was dependent on seawater concentrations where formations of Pb oxides and adsorption on the MgO surface were predominant in solutions with low and high salinity, respectively. The release of As fixed with MgO significantly increased in seawater compared to freshwater, although the amount of As desorbed accounted for <0.2% of total As.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Initial concentrations of Pb and As in freshwater controlled the characteristics of the reaction product of MgO. </LI> <LI> Removal of aqueous Pb and As by MgO was increased by the seawater concentration. </LI> <LI> Surface adsorption of As on MgO is predominant in 0–3.6% seawater. </LI> <LI> The retention mechanism of Pb was dependent on seawater concentrations. </LI> <LI> Release of As fixed with MgO significantly increased more in seawater than freshwater. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Tomohito Kameda,Tetsu Shinmyou,Toshiaki Yoshioka 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.36 No.-
1-Hydroxyethane-1,1-diphosphonic acid intercalated Li–Al layered double hydroxide (HEDP Li–Al LDH)was prepared by co-precipitation. HEDP Li–Al LDH was found to take up Nd3+ and Sr2+ ions from aqueoussolutions; this can be attributed to the metal-chelating functions of the HEDP ions in the interlayers ofHEDP Li–Al LDH. Sr2+ uptake by HEDP Li–Al LDH was larger than Nd3+ uptake. This is probably becausethe uptake of one mole of Nd3+ by HEDP Li–Al LDH requires two times the number of moles of HEDP ionsthan the uptake of one mole of Sr2+. The mass-transfer-controlled shrinking core model described theuptake behavior better than the surface reaction-control model. HEDP ions in the HEDP Li–Al LDHinterlayer rapidly form chelate complexes with Nd3+ or Sr2+, as a result of which the transfer of Nd3+ orSr2+ through the product layer is rate limiting. Furthermore, this reaction mechanism can be described bya Langmuir-type adsorption phenomenon, indicating that this reaction involves chemical adsorption;this is consistent with the formation of chelate complexes between Nd3+ or Sr2+ and HEDP ions in theinterlayers of HEDP Li–Al LDH. The control of chelate ions in the interlayer of Li–Al LDH leads to thecontrol of the preferential uptake of metal ions.
Treatment of hydrochloric acid using Mg–Al layered double hydroxide intercalated with carbonate
Tomohito Kameda,Masahito Tochinai,Toshiaki Yoshioka 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.39 No.-
Mg–Al layered double hydroxide intercalated with CO32 (CO3 Mg–Al LDH) was found to take up onlylow amounts of Cl during the treatment of hydrochloric acid. Low pH promotes the removal of Cl . HClis considered to react with CO32 in the interlayers of Mg–Al LDH as a result of which Cl is probablyintercalated in the interlayers. High pH of the Mg–Al LDH suspension leads to a lower extent of reactionbetween HCl and Mg–Al LDH, owing to the neutralization of the acid. We can state that the adsorption ofCl on Mg–Al LDH is best described by the Dubinin–Radushkevich adsorption isotherm. The maximumadsorption amounts were calculated to be 1.4 and 0.6 mmol/g for CO3 Mg–Al LDH with Mg/Al molarratios of 2 and 4, respectively, whereas the adsorption energies were calculated to be 82 and 124 kJ/mol,respectively. In summary, the removal of Cl is caused by both the reaction between hydrochloric acidand CO32 in the interlayers of Mg–Al LDH as well as anion exchange between the HCO3produced and adifferent Cl ion in hydrochloric acid. This explains why the adsorption is best expressed by the D–Radsorption isotherm, which assumes a heterogeneous surface and non-constant adsorption potential
Tomohito Kameda,Yoshiaki Umetsu 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-
Carbonate ion-intercalated Mg–Al layered double hydroxides (CO3-type Mg–Al LDHs) were prepared by using various methods to mix a solution of Mg(NO3)2 and Al(NO3)3 with an alkaline solution, and the particle properties of the obtained samples were compared. By mixing stoichiometric quantities of Mg2+, Al3+, and OH according to the coprecipitation reaction for preparing CO3-type Mg–Al LDHs, Mg2+ and Al3+ in solution were quantitatively precipitated, and the Mg/Al molar ratios of the obtained Mg–Al LDHs were equal to those of the solution, irrespective of the preparation method. However, the different preparation methods resulted in different particle properties, namely, different particle size distributions, particle morphologies, and sedimentation properties were observed. These differences were attributed to different formation processes for Mg–Al LDH. The ideal preparation method was determined to involve the addition of Mg(NO3)2 and Al(NO3)3 solution to Na2CO3 solution at a constant pH, which was achieved by adjusting with NaOH solution. This preparation method resulted in the formation of CO3-type Mg–Al LDH particles with uniform primary particles, good sedimentation properties, and a narrow distribution of secondary particle aggregates. Such characteristics make these Mg–Al LDHs excellent candidates for wastewater treatment.
Takayuki Kameda,Hiroshi Bandow 한국대기환경학회 2021 Asian Journal of Atmospheric Environment (AJAE) Vol.15 No.1
Nitrotriphenylenes (NTPs), which include the highly mutagenic isomer 2-nitrotriphenylene (2-NTP), have been detected in airborne particles. From a public hygienic point of view, it is necessary to study the environmental occurrence of NTPs in detail. In this study, concentrations of five nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) including NTPs in airborne particles and of nitrogen oxides (NOx; NO+NO2) and carbon monoxide (CO), at a location in South Osaka, Japan, were measured at 3 h intervals. It was found that the diurnal variations in the concentrations of 1-nitropyrene (1-NP), NOx, and CO were similar, being high early in the morning and late in the evening. This finding indicates that the occurrence of 1-NP is affected significantly by primary emissions, particularly by automotive emissions. The concentration change in 1-nitrotriphenylene was similar to that of 2-nitropyrene produced by an atmospheric OH radicalinitiated reaction. On the contrary, the variations in the concentrations of 2-nitrofluoranthene (2-NF) and 2-NTP were significantly different from those of the other nitro-PAHs, i.e., their concentrations increased during the nighttime, suggesting that neither 2-NF nor 2-NTP was emitted from the primary sources, but were formed via the NO3 radicalinitiated nitration of the parent fluoranthene and triphenylene (TP) in the atmosphere. Based on the ambient concentration of 2-NTP and the reported rate constant for the reaction of TP with NO3 radicals, the yield of 2-NTP from the gas-phase NO3 radical-initiated reaction of TP was estimated to be 23%.
Chizu Kameda,Hideaki Miwa,Ryohei Kawabata,Daiki Marukawa,Masahiro Murakami,Shingo Noura,Junzo Shimizu,Junichi Hasegawa 대한소화기내시경학회 2018 Clinical Endoscopy Vol.51 No.4
An inflammatory fibroid polyp (IFP) is a mesenchymal tumor of the gastrointestinal tract. IFPs in the small intestine are the mostfrequently detected with symptoms, such as abdominal pain and tarry stool due to intussusception. Accordingly, few studies havereported jejunal IFP as a cause of occult gastrointestinal bleeding (OGIB) diagnosed via both of capsule endoscopy (CE) and doubleballoonenteroscopy (DBE). A 68-year-old woman presented with a progression of anemia and a positive fecal occult blood test result. Esophagogastroduodenoscopy and total colonoscopy findings were unremarkable. CE revealed a tumor with bleeding in the jejunum. DBE also revealed a jejunal polypoid tumor. Bleeding from the tumor seemed to have caused anemia. The patient underwent partiallaparoscopic resection of the jejunum, including resection of the tumor. The tumor was histopathologically diagnosed as IFP. To ourknowledge, this is the first reported case of laparoscopic resection of jejunal IFP with OGIB diagnosed via CE and DBE preoperatively.