Metal–organic frameworks (MOFs) for the removal of emerging contaminants from aquatic environments

Dhaka, Sarita,Kumar, Rahul,Deep, Akash,Kurade, Mayur B.,Ji, Sang-Woo,Jeon, Byong-Hun Elsevier 2019 Coordination chemistry reviews Vol.380 No.-

<P><B>Abstract</B></P> <P>Metal–organic frameworks (MOFs) have gained attention as promising materials for aqueous-phase sorptive removal of emerging contaminants (ECs). Attributes such as large adsorption capacity, high surface area, tunable porosity, hierarchical structure, and recyclability give MOFs an edge over conventional adsorbents. The poor stability of MOFs in water is a major challenge to their real-world environmental application. The performance of MOFs and their selectivity toward targeted pollutants for removal can be regulated by judicious selection of metal ion and organic linker. A range of water-stable MOFs (e.g., MIL-53, MIL-100, MIL-101, UiO-66, and MIL-125) and their composites with other materials have been reported to remove the ECs from water. The present review critically addressed the performance of MOFs for the adsorptive removal of different categories of ECs from water and the adsorption mechanisms involved. The performance of MOFs compared with other adsorbents has also been discussed. This body of rapidly developing research signifies the emerging importance of MOFs in environmental applications and provides a future direction for the development of treatment technology to effectively remove ECs from aqueous environments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MOFs offer great opportunities in environmental remediation of different pollutants. </LI> <LI> MOFs are potential adsorbents for water purification. </LI> <LI> Strategies to improve the aqueous phase stability of MOFs are reviewed. </LI> <LI> Performance of MOFs in aqueous phase emerging contaminants removal are highlighted. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Degradation of ethyl paraben in aqueous medium using advanced oxidation processes: Efficiency evaluation of UV-C supported oxidants

Dhaka, Sarita,Kumar, Rahul,Lee, Sang-hun,Kurade, Mayur B.,Jeon, Byong-Hun Elsevier 2018 Journal of Cleaner Production Vol.180 No.-

<P><B>Abstract</B></P> <P>UV-C-mediated advanced oxidation processes (AOPs) for the enhanced degradation of ethyl paraben (EP) in the presence of oxidants such as persulfate (PS), hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) and peroxymonosulfate (PMS) were systematically investigated. The AOP treatments showed 98.1%, 97.0% and 81.3% degradation of EP with rates of 0.0373, 0.0339, and 0.0202 min<SUP>−1</SUP> within 90 min for UV/PS, UV/H<SUB>2</SUB>O<SUB>2</SUB> and UV/PMS, respectively. Degradation rates of EP increased with higher initial dosages of oxidant(s), while the opposite trend was observed in the case of increasing initial EP concentration. Maximum EP removal was achieved at pH 6.5 for UV/PS and UV/PMS and at pH 3 for UV/H<SUB>2</SUB>O<SUB>2</SUB>. Humic acid significantly retarded the degradation of EP. Chloride (Cl<SUP>−</SUP>) and carbonate (CO<SUB>3</SUB> <SUP>2−</SUP>) suppressed reaction rates using UV/PS and UV/H<SUB>2</SUB>O<SUB>2</SUB> systems, whereas they elevated the degradation rates with UV/PMS treatment. Degradation of EP in each of the UV-C based AOPs followed pseudo-first-order kinetics. The use of ethanol and t-butyl alcohol as scavengers revealed that HO<SUP> </SUP> and ▪ radicals were the major reactive radicals in UV/H<SUB>2</SUB>O<SUB>2,</SUB> UV/PS, and UV/PMS treatments. The efficiency (according to electrical energy per order and total cost per cubic meter) of the systems followed the order UV/PS > UV/H<SUB>2</SUB>O<SUB>2</SUB> > UV/PMS. Thus, UV/PS process was more efficient and economical for EP degradation than the other processes examined in this study.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Aqueous phase ethyl paraben (EP) degradation using UV-C based AOPs was investigated. </LI> <LI> EP degradation was pH dependent and followed pseudo-first-order kinetics. </LI> <LI> Anions (Cl<SUP>−</SUP>, CO 3 2 − ) suppressed EP degradation in UV/PS and UV/H<SUB>2</SUB>O<SUB>2</SUB> systems. </LI> <LI> HO<SUP> </SUP> and ▪ radicals were predominant in UV/H<SUB>2</SUB>O<SUB>2</SUB> and UV/PS/PMS processes </LI> <LI> Efficiency of the processes followed the order: UV/PS > UV/H<SUB>2</SUB>O<SUB>2</SUB> >UV/PMS. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Aqueous phase degradation of methyl paraben using UV-activated persulfate method

Dhaka, Sarita,Kumar, Rahul,Khan, Moonis Ali,Paeng, Ki-Jung,Kurade, Mayur B.,Kim, Sun-Joon,Jeon, Byong-Hun Elsevier 2017 Chemical Engineering Journal Vol.321 No.-

<P><B>Abstract</B></P> <P>Methyl paraben (MP), a widely used preservative, exhibits endocrine-disrupting properties with estrogenic activities. The aqueous phase degradation of MP, using UV-activated persulfate method, was investigated in the present study. The combination of UV irradiation and persulfate anion successfully degraded MP showing 98.9% removal within 90min. A quenching experiment using ethanol (EtOH) and <I>tert</I>-butyl alcohol (TBA) showed the presence of both radicals (OH<SUP> </SUP> and SO<SUB>4</SUB> <SUP> –</SUP>) in the system; near neutral pH SO<SUB>4</SUB> <SUP> –</SUP> radical was the major species. The influence of various factors such as persulfate dose, initial MP concentration, solution pH, and water matrix components on the degradation kinetics was examined in view of the practical applications of the developed process. The degradation rate of MP was considerably increased as the amount of persulfate increased. The degradation of MP in the UV/persulfate system was pH dependent and more promising near neutral pH (6.5) conditions. The presence of anions such as Cl<SUP>−</SUP>, HPO<SUB>4</SUB> <SUP>2−</SUP> and HCO<SUB>3</SUB> <SUP>−</SUP> showed inhibitory effect towards MP degradation. The presence of humic acid also suppressed the degradation efficiency of MP. The reaction rate followed pseudo-first-order kinetics for all of the degradations. The degradation of MP by UV/persulfate treatment led to the production of seven transformation byproducts, which were identified using ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS). A degradation pathway for MP degradation was also proposed. The results of the present study reveal that the UV/persulfate process could be an effective approach to remove MP from aqueous solutions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Aqueous phase MP degradation using UV/persulfate method was investigated. </LI> <LI> Degradation rate of MP followed pseudo-first-order kinetics. </LI> <LI> MP degradation was pH dependent. </LI> <LI> HCO<SUB>3</SUB> <SUP>−</SUP>, HPO<SUB>4</SUB> <SUP>2−</SUP> and humic acid exhibited inhibitory effect on MP degradation. </LI> <LI> Hydroxylation and hydrolysis were possible pathways of degradation of MP. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Remediation of cyanide-contaminated environments through microbes and plants: a review of current knowledge and future perspectives

RAHUL KUMAR,Shouvik Saha,Sarita Dhaka,Mayur B. Kurade,강찬웅,백승한,전병훈 한국자원공학회 2017 Geosystem engineering Vol.20 No.1

Mining industry has been using cyanide for more than ten decades to recover precious metals such as gold and silver. The presence of cyanide in the environment has long been a matter of concern due to its high toxicity to human, animal, and aquatic life. The available treatment processes either physical or chemical are suffered with issues such as operating conditions, generation of secondary pollution, and lack of cost effectiveness. A number of micro-organisms are capable to consume cyanide as a source of carbon and nitrogen, and convert it into ammonia and carbonate. Some plants are also efficient in cyanide attenuation process. Bioremediation of cyanide might be an efficient, cost-effective, eco-friendly, and an attractive alternative to the conventional physical and chemical processes. This paper reviews the recent advances in remediation of cyanide contaminated tailings via micro-organisms and plants. Aspects such as speciation, toxicity, source, and degradation mechanisms of cyanide are discussed. Factors affecting functioning of micro-organisms and plants as bioremediation agents are also highlighted.