Exploring the complex removal behavior of natural organic matter upon N-doped reduced graphene oxide-activated persulfate via excitation-emission matrix combined with parallel factor analysis and size exclusion chromatography

Maqbool, Tahir,Bae, Sungjun,Hur, Jin Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.347 No.-

<P><B>Abstract</B></P> <P>Metal-free oxidative degradation by persulfate (PS) is an emerging process as green chemistry without any toxic metal leaching to aquatic environments but has never been explored for natural organic matter (NOM) removal to date. In this study, nitrogen-doped reduced graphene oxide (NrGO) was applied as a catalyst first to investigate the degradation behavior of NOM. A parallel system was also examined without PS for non-oxidative interaction. For three tested NOM, the extent of the removal increased with the addition of NrGO, and the removal rates were consistently higher for the systems with versus without PS (by 25–102%). Specific ultraviolet absorbance (SUVA) exhibited declining trends with NrGO for both oxidative and non-oxidative systems. Up to 86.9%, 59.9%, and 60.3% reduction in SUVA values were found for the oxidative removal of Suwannee River natural organic matter, Suwannee River humic acid, and Suwannee River fulvic acid, respectively. The excitation-emission matrix combined with parallel factor analysis (EEM-PARAFAC) decomposed fluorescent NOM into two fulvic-like (C1 and C2) and two humic-like (C3 and C4) components. Results implied that more hydrophobic and more condensed aromatic NOM constituents might be preferably removed by both oxidation and adsorption with the greater removal tendency shown for the humic versus the fulvic-like components. Size exclusion chromatography (SEC) demonstrated that large size molecules were more effectively removed by the oxidative versus the non-oxidative interactions with NrGO. Comparative results revealed that adsorption likely played a critical role in determining the preferential removal tendency of the metal-free oxidation toward heterogeneous NOM structures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study first explored metal-free oxidation of NOM. </LI> <LI> NrGO-driven PS activation effectively removed NOM via adsorption and oxidation. </LI> <LI> Preferential removal of aromatic and large size NOM molecules was found. </LI> <LI> Adsorption plays a critical role in NOM removal via a non-radical pathway. </LI> <LI> Humic-like fluorescence can be a good surrogate for tracking NOM removal. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

천연광물의 양극성 표면개질을 이용한 상수원수 중 중금속제거 특성

김남열,김영희 한국환경보건학회 2019 한국환경보건학회지 Vol.45 No.6

Objectives: The most commonly detected heavy metals in rocks and soils, including Pb, Cd, Cu, Fe, Mn and As, are representative pollutants discharged from abandoned mines and have been listed as potential sources of contamination in drinking water. This study focused on increasing the removal efficiency of heavy metals from drinking water resources by surface modification of natural adsorbents to reduce potential health risks. Methods: Iron oxide coating and graft polymerization with zeolites and talc was conducted for bipolar surface modification to increase the combining capacity of heavy metals for their removal from water. The removal efficiency of heavy metals was measured before and after the surface modification. Results: The removal efficiency of Pb, Cu, and Cd by surface modified zeolite showed 100, 92, and 61.5%, respectively, increases compared to 64, 64, and 38% for non-modified zeolite. This implies that bipolar surface modified natural adsorbents have a good potential use in heavy metal removal. The more interesting finding is the removal increase for As, which has both cation and anion characteristics showing 27% removal efficiency where as non-modified zeolite showed only 2% removal. Conclusions: Zeolite is one of the most widely used adsorptive materials in water treatment processes and bipolar surface modification of zeolite increases its applicability in the removal of heavy metals, especially As.

천연 및 전처리 제올라이트에 의한 2 가 중금속 이온 제거능의 비교 검토

감상규,김덕수,이민규 한국환경과학회 1999 한국환경과학회지 Vol.8 No.3

The three domestic natural zeolites(Yong dong-ri (Y), Daesin-ri (D), Seogdong-ri (S)) harvested in Kyeongju-shi and Pohang-shi, Kyungsangbug-Do, were pretreated with each of the NaOH, Ca(OH)_2, and NaOH following HCl solutions, and the removal performances of divalent heavy metals(Cu, Mn, Pb, and Sr) for natural and pretreated zeolites were investigated and compared in the single and mixed solutions. The natural zeolite-heavy metal system attained the final equilibrium plateau within 20 min, irrespective of initial heavy metal concentration. The heavy metal uptakes increased with increasing initial heavy metal concentration and pH. The heavy metal uptakes for natural zeolites decreased in the following sequences : D>Y>S among the natural zeolites; Pb>Cu>Sr>Mn among the heavy metals. The pretreated zeolites showed higher heavy metal removal performances than natural zeolites and decreased in the order of NaOH, NaOH following HCl, Ca(OH)_2 treatment among the pretreatment methods. The heavy metal ion exchange capacity by natural and pretreated zeolites was described either by Freundlich equation or Langmuir equation, but it followed the former better than the latter. The heavy metal uptakes for natural zeolites decreased in the mixed solution, in comparing with those in the single solution and especially, the manganese uptake decreased greatly in the mixed solution. The pretreated zeolites showed the improved removal performances of heavy metals in the mixed solution than in the single solution and the heavy metal uptakes by those in the mixed solution showed the same trends in the single solution among the chemical treatment methods and heavy metals.

Electrochemical denitrification of metal-finishing wastewater:Influence of operational parameters

심주현,김정환,서형준 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.4

Experimental results are presented for the electrolytic ChemDen (Chemical-Denitrification) process which was designed to investigate the effect of operational parameters on the nitrate (NO3−) removal from metal-finishing wastewater. The parameters included electrode materials, electrode gap, reducing agent, hydraulic retention time (HRT)and recycle ratio in the single electrolytic ChemDen reactor for lab-scale tests. The removal efficiency of nitrate is based upon a non-biological process which consists of chemical and electrolytic treatment. Results showed that removal efficiency of nitrate was highest when the zinc (Zn) electrodes were used for both anode and cathode. In the case of insoluble electrode, combining Pt anode with Ti cathode provided great improvement of nitrate removal. For the Pt-Ti electrode combination, increasing electrode gap tended to increase removal efficiency of nitrate significantly. However, no further increase in the nitrate removal was observed when the electrode gap was longer than 10mm. Using sulfamic acid and Zn metal powder as reducing agents for the electrolytic ChemDen reaction, highest nitrate removal was achieved when the mole ratio of Zn : sulfamic acid : nitrate was 1.2 : 1 : 1. Remarkable improvement in the nitrate removal was also observed with increasing HRT from 10 to 30 min, while the effectiveness was limited when HRT was increased to 60 min. Recycling in electrolytic ChemDen reactor affected nitrate removal positively because it could improve both dispersion and reuse of Zn metal powder as reducing agent in the reactor. Recycling effects were thought to be associated with increasing surface reactivity of the Zn metal powder in the electrolytic ChemDen reactor.

Heavy metal removal from aqueous solution by granular hydrated Portland cement

Peng Cheng,Yongxiang Ren,Lei Yang,Rituan Li,Xue Wang,Bin Li,Honglin Yuan 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.12

Granular hydrated Portland cement (HPC) was prepared as adsorbent to remove heavy metals in aqueoussolution. Batch experiment results confirmed that heavy metals were removed through a combination of adsorptionand precipitation. Adsorption played a more important role in the initial stage of the removal process or at lower concentrationsof the heavy metals. After adsorption equilibrium was obtained in two days, the removal process continuedfor about three days due to the precipitation. Besides precipitation, the maximum Langmuir adsorption capacity reached132.27, 87.14, 123.43 and 112.05mg/g for Pb, Cu, Zn, and Cd, respectively. When various heavy metals coexisted, theremoval capacity followed the order of Cu>Pb>Cd>Zn. The adsorption on the surfaces of HPC was mainly governedby surface precipitation and Ca2+ exchange, as suggested by XRD, SEM-EDS and released Ca2+ results. Most of theadsorbed heavy metals on the HPC and the precipitation formed in the liquid phase were stable under neutral andalkaline conditions. Overall, HPC particles exhibited a large potential for heavy metal removal. When cement-relatedmaterials containing HPC are employed for heavy metal removal, the dissolution of the precipitate at low pH mightfacilitate the migration of the heavy metals.

Mixed metal oxide coated polymer beads for enhanced phosphorus removal from membrane bioreactor effluents

Park, Hak-Soon,Kwak, Se-Hoon,Mahardika, Dedy,Mameda, Naresh,Choo, Kwang-Ho Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.319 No.-

<P><B>Abstract</B></P> <P>Membrane bioreactors are effective and attractive for wastewater reclamation and reuse, but phosphorus polishing is required to meet more stringent environmental regulations. Mixed metal oxide coated beads composed of Fe-Ti bimetal oxides on a sulfonated polymer were fabricated, characterized, and tested for phosphorus removal from membrane bioreactor effluents. Ti doping substantially enhanced the adsorption rate and capacity of the coated beads, possibly due to more positively charged surfaces. The mixed metal oxide coated beads were highly selective to phosphate ions (selectivity factor >25) against background ions (e.g., Cl<SUP>−</SUP>, NO<SUB>3</SUB> <SUP>−</SUP>, and SO<SUB>4</SUB> <SUP>2−</SUP>), although they were less selective against bicarbonate and organics. Regenerated beads showed greater adsorption performance than the virgin ones. Ca binding to mixed metal oxide layers was responsible for enhanced phosphorus sorption, presumably resulting from the formation of calcium phosphate. The phosphorus recovery from the exhausted column adsorber was successful with alkaline solution (e.g., >90% P was recovered at a NaOH load of 0.2eq/L bed. Using mixed metal oxide chemically anchored on polymer beads for phosphorus sorption would be a promising complement to biological phosphorus removal.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fe-Ti bimetal oxide-coated composite beads were investigated for phosphorus removal. </LI> <LI> A small amount of Ti dopant enhanced phosphorus removal significantly. </LI> <LI> Phosphate selectivity was remarkable against common background anions. </LI> <LI> Ca binding to the coated bead improved phosphate sorption. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

pH 변화에 따른 중금속 수용액의 반응 메커니즘

송수욱 ( Song Su Ug ),정호진 ( Jeong Ho Jin ) 한국수처리학회 2004 한국수처리학회지 Vol.12 No.1

This study was designed to set up a theoretical mechanism for removal and separation of heavy metal ions from aqueous solutions by analysing reaction between pH and heavy metal ions, and to offer useful data for treatment applications of wastewater containing heavy metals in the future. The obtained results are as follows: Each heavy metal ion has a unique curve between pH and residual heavy metal concentration. When two types of heavy metals are complexed, the reaction rate between OH- and heavy metal ion is more affected by ionization strength rather than competitive reaction. When three types of heavy metals are combined, the ultra-fine particle is formed at about 1-2 lower PH than in the case that independently existed. This is because chemical reaction was caused by complicated reactions of pH of the minimum soluble product, ionization strength, and competitive reaction. The electric field makes ultra-fine particles having a very small amount of charge move more easily than large colloidal particles. Therefore, this study shows that it is possible to improve the efficiency of selective flocculation by electrolysis at PH which forms ultra-fine particles of metal-hydroxides by the application of the results.

On-Line Prediction of Impulse Spark and Arc Discharge Removals of Metal Bond in Dry Electrical Discharge Dressing of Diamond Grinding Wheel

Yanjun Lu,Jiajing Sun,Xiaoyu Wu,Fumin Chen 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.2

The electrical discharge is able to realize efficient dressing for metal-bonded diamond wheel, but the monitoring and prediction of dressing status have been technical bottleneck in industrialization. Hence, the metal bond removal model of impulse spark and arc discharges is proposed to realize on-line monitoring and prediction for micro grain protrusion on diamond grinding wheel surface. The relationship between microremovals of metal bond and impulse spark and arc discharge parameters was investigated for controllable dressing. First, the static and dynamic impulse discharge experiments were carried out to reveal metal bond removal mechanisms of impulse spark and arc discharges; then the relationship between characterized impulse discharge parameters and removal of metal bond was quantitatively analyzed; finally, the dry electro-contact discharge (ECD) dressed coarse diamond wheels were applied to perform smooth surface and mirror grinding of optical glass and mold steels against mechanical dressed wheels. It is found that the critical transition value of arc discharge to spark discharge under static discharge and dynamic discharge conditions were 0.059 and 0.038, respectively. In comparison with mechanical dressing, the dry ECD can obtain higher grain protrusion height to improve ground surface quality, leading to a microscopic smooth surface of BAK3 optical glass and macroscopic mirror-like surface of model steels. It is confirmed that the established relationship model can be effectively used to on-line predict the removal of metal bond with the average prediction error of 10.1% and microscopic grain protrusion by characterized impulse discharge parameters.

족관절 골절 치료에 사용한 금속 내고정물 제거 수술 시 시행한 균 배양 검사의 결과

정형진,배서영,유재하,Chung, Hyung-Jin,Bae, Su-Young,Yu, Jae-Ha 대한족부족관절학회 2014 대한족부족관절학회지 Vol.18 No.2

Purpose: The purpose of this study is to report the results of culture test at the time of removal of metal devices used for management of ankle fractures and for analysis of contributing factors. Materials and Methods: We reviewed medical records of 132 patients with lower tibia and ankle fracture who had their metal devices removed during the period from January 2010 to February 2014. Patients with clinical signs of infection were excluded. Culture test was performed by taking the granulation tissue around the metal device at the time of removal. We divided the subjects into two groups, culture positive and negative. We then performed a retrospective review of each medical record of multiple factors that might contribute to the culture results, including laboratory results, medical history, material and size of metal device, indwelling period, and whether or not it was open injury. Results: Among 132 cases, six were culture positive. Enterococcus was detected in two cases and the others were Staphylococcus. No significant difference in medical history of patients and laboratory results, including C-reactive protein level, was observed between the culture positive and negative group. Culture positive rate was 5.4% in titanium and 3.9% in stainless steel. In terms of metal size, culture positive rate was 5.1% in small plates, 6.7% in large plates, and culture negative in intramedullary nails. The average indwelling period of metal device was 61.5 weeks in the culture positive group, and 68.6 weeks in the negative group. Nine cases were open fractures and all were in the culture negative group. Conclusion: Whether or not the culture result was positive, there were no meaningful contributing factors. Presence of bacterium on the metal device could not be screened by any laboratory results or other factors.

한약중 중금속 함량 및 용출에 관한 연구

김종우,심상범,홍남두,김남재,류재환 WHO COLLABORATING CENTRE FOR TRADITIONAL MEDICINE 1996 東西醫學硏究所 論文集 Vol.1996 No.-

Quantitative analysis of 11 kinds of metals was performed in 12 species of commercially available crude drugs by means of inductively coupled plasma spectrophotometer(ICPS). Estimation of the elution rate of metals in decoction prepared from crude drugs and the proportions of metal contents in precipitate and supernatant of decoction prepared from crude drugs which were added 5 ppm of seven standard metals: Cr, Mn, Co, Ni, Cu, Cd, Pb were quantitatively analyzed. all samples were digested with wet oxidation method by nitric acid and perchloric acid. Contents of metals in samples were analyzed by ICPS. Metal contents in those specimens were summarized as follows: Mg and Ca contents were higher than other metals, and Mg and Ca contents of Menthae Herba and Fe content of Asiasari Raidx were higher than other specimens. Cd, Cr, Pb, Ni and Co were not detected in any crude drugs. Means of elution rate of Mg, Ca, Mn, Fe and Zn in decoction from crude drugs were respectively 53.2%, 30.7%, 39.2%, 12.9% and 42.2%. Especially, elution rate of metals from Angelicae Radix and Galla Rhois were high, but from Aurantii nobils Pericarpium was low. The proportion of metal contents in precipitate of decoction prepared from all specimens added 5 ppm of Pb, Cu, Cd, Cr, Mn, Ni and Co were respectively 95.8%, 83.2%, 54.7%, 48.8%, 31.6%, 31.1% and 29.8%. The removal rate of metals in precipate of decoction prepared from Galla Rhois was low, but from Phellodendri Cortex was high.