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Mallampati, Srinivasa Reddy,Mitoma, Yoshiharu,Okuda, Tetsuji,Simion, Cristian,Lee, Byeong Kyu Elsevier 2015 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.139 No.-
<P><B>Abstract</B></P> <P>Although direct radiation induced health impacts were considered benign, soil contamination with <SUP>137</SUP>Cs, due to its long-term radiological impact (30 years half-life) and its high biological availability is of a major concern in Japan in the aftermath of the Fukushima nuclear power plant disaster. Therefore <SUP>137</SUP>Cs reduction and immobilization in contaminated soil are recognized as important problems to be solved using suitable and effective technologies. One such thermal treatment/vitrification with nanometallic Ca/CaO amendments is a promising treatment for the ultimate immobilization of simulated radionuclide <SUP>133</SUP>Cs in soil, showing low leachability and zero evaporation. Immobilization efficiencies were 88%, 95% and 96% when the <SUP>133</SUP>Cs soil was treated at 1200 °C with activated carbon, fly ash and nanometallic Ca/CaO additives. In addition, the combination of nanometallic Ca/CaO and fly ash (1:1) enhanced the immobilization efficiency to 99%, while no evaporation of <SUP>133</SUP>Cs was observed. At lower temperatures (800 °C) the leachable fraction of Cs was only 6% (94% immobilization). Through the SEM–EDS analysis, decrease in the amount of Cs mass percent detectable on soil particle surface was observed after soil vitrified with <I>n</I>Ca/CaO + FA. The <SUP>133</SUP>Cs soil was subjected to vitrified with <I>n</I>Ca/CaO + FA peaks related to Ca, crystalline phases (CaCO<SUB>3</SUB>/Ca(OH)<SUB>2</SUB>), wollastonite, pollucite and hematite appeared in addition to quartz, kaolinite and bentonite, which probably indicates that the main fraction of enclosed/bound materials includes Ca-associated complexes. Thus, the thermal treatment with the addition of nanometallic Ca/CaO and fly ash may be considered potentially applicable for the remediation of radioactive Cs contaminated soil at zero evaporation, relatively at low temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Vitrification with nanometallic Ca/CaO is a promising treatment for Cs in soil. </LI> <LI> Dynamic Cs immobilization and zero evaporation were done by nanometallic Ca/CaO. </LI> <LI> By SEM analysis the amount of cesium detectable on soil particle surface decreases. </LI> <LI> Leachable cesium concentrations reduced, lower than the standard regulatory limit. </LI> <LI> Nanometallic Ca/CaO is unique amendment for the remediation of Cs in soil. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>SEM–EDS element maps of <SUP>133</SUP>Cs contaminated soil before and after thermal treatment at 1200 °C with different addictives. Color intensity for Cs is from 0 to 100 (low to high).</P> <P>[DISPLAY OMISSION]</P>
( Srinivasa Reddy Mallampati ),( Chi-hyeon Lee ),( Nguyen Thi Thanh Truc ),( Byeong-kyu Lee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-
One of the major problems in incineration for thermal recycling or heat melting for material recycling is the polyvinyl chloride (PVC) contained in ASR/ESR plastics. This is due to the production of hydrogen chloride, chlorine gas, dioxins, and furans originated from PVC. Therefore, the separation of PVC from ASR/ESR waste plastics is necessary before recycling. The separation of heavy polymers (PVC 1.42, PMMA 1.12, PC 1.22 and PET 1.27 g/cm<sup>3</sup>) from light ones (PE and PP 0.99 g/cm<sup>3</sup>) can be achieved on the basis of their density in wet gravity separation. However it is difficult to separate PVC from other heavy polymers basis of density. There are no simple and inexpensive techniques to separate PVC from other plastics. If hydrophobic the PVC surface is selectively changed into hydrophilic, where other polymers still have hydrophobic surface, flotation process can separate PVC from others. In the present study, the selective surface hydrophilization of polyvinyl chloride (PVC) by microwave treatment after alkaline/acid washing and with activated carbon was studied as the pre-treatment of its separation by the following froth flotation. In presence of activated carbon as absorbent, the microwave treatment could selectively increase the hydrophilicity of the PVC surface (i.e. PVC contact angle decreased about 19°) among other plastics mixture. At this stage, 100% PVC separation from other plastics could be achieved by the combination of the pre- microwave treatment with activated carbon and the following froth floatation. The hydrophilization of PVC by surface analysis would be due to the hydrophilic groups produced by microwave treatment with activated carbon. The effect of optimum condition and detailed mechanism onto separation efficiency in the froth floatation was also investigated.
( Srinivasa Reddy Mallampati ),( Min Hee Park ),( Je Haeng Heo ) 한국폐기물자원순환학회(구 한국폐기물학회) 2016 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2016 No.-
The presence of chlorinated/brominated halogenated plastics in automobile and electronic waste shredder residue (ASR/ESR), can contribute to the formation of hazardous chlorinated/brominated dioxins when subjected to incineration or thermal recycling. Treatment by a nanometallic Ca/CaO composite has been found to selectively hydrophilize the surface of polyvinyl chloride (PVC), enhancing its wettability and thereby promoting its separation from E-waste plastics by means of froth flotation. The treatment considerably decreased the water contact angle of PVC, by about 18°. The SEM images of the PVC plastic after treatment displayed significant changes in their surface morphology compared to other plastics. The SEM-EDS results reveal that a markedly decrease of [Cl] concentration simultaneously with dramatic increase of [O] on the surface of the PCV samples. XPS results further confirmed an increase of hydrophilic functional groups on the PVC surface. Froth flotation at 100 rpm mixing speed was found to be optimal, separating 100% of the PVC into a settled fraction of 96.4% purity even when the plastics fed into the reactor were of nonuniform size and shape. The total recovery of PVC-free plastics in E-waste reached nearly 100% in the floated fraction, significantly improved from the 20.5 wt% of light plastics that can be recovered by means of conventional wet gravity separation. The reagent employed during treatment is very small, and further surface contaminant removal on recycled E-waste plastics surfaces makes the developed process simple, effective and green.
( Min Hee Park ),( Yu Ri Lee ),( Srinivasa Reddy Mallampati ) 한국폐기물자원순환학회(구 한국폐기물학회) 2016 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2016 No.-
Due to its high heterogeneity and variable composition of hazardous substances, such as heavy metals, polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs) and other persistent organic pollutants (POPs), automobile shredder residues (ASR) can be classified as hazardous waste. In Korea, incineration has become an important method for treating municipal and industrial solid wastes, including ASR. However, ASR thermal process removes some of the organic material but concentrates the heavy metals and POPs present in the ASR, ash residues. Therefore, heavy metals immobilization treatment is needed before these residues from the ASR incinerator can be disposed or used. This study was conducted to synthesize and apply a novel nano-size calcium dispersed reagent as an immobilization material for heavy metal-contaminated ASR thermal residues in dry condition. Grinding with a nanometallic Ca/CaO/PO<sub>4</sub> dispersion mixture can achieve about 95-99% of heavy metal immobilization. The results highlight the low quantity of heavy metals leached from ASR residues after treatment with nanometallic Ca/CaO, that was found to be lower than the regulatory limit for hazardous waste landfills. SEM/EDS morphology and elemental composition results reviled that the amounts of heavy metals detectable on the ASR thermal residue surface decreased and the Ca/PO4 mass percent increased. X-ray diffraction (XRD) pattern indicated that the main fraction of enclosed/bound materials on ASR residue included Ca/PO<sub>4</sub> - associated crystalline complexes, and that immobile Ca/PO<sub>4</sub> salts remarkably inhibited the desorption of heavy metals from ASR residues. These results support the potential use of nanometallic Ca/CaO/PO<sub>4</sub> as a simple, suitable and highly efficient material for the gentle immobilization of heavy metals in hazardous ASR thermal residue in dry condition.
Thanh Truc, Nguyen Thi,Lee, Chi-Hyeon,Lee, Byeong-Kyu,Mallampati, Srinivasa Reddy Elsevier 2017 Journal of hazardous materials Vol.321 No.-
<P><B>Abstract</B></P> <P>Polyvinyl chloride (PVC) containing chlorine can release highly toxic materials and persistent organic pollutants if improperly disposed of. The combined technique of powder activated carbon (PAC) coating and mild heat treatment has been found to selectively change the surface hydrophobicity of PVC, enhancing its wettability and thereby promoting its separation from heavy plastic mixtures included polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS) and acrylonitrile butadiene styrene (ABS) by means of froth flotation. The combined treatments helped to rearrange the surface components and make PVC more hydrophobic, while the remaining plastics became more hydrophilic. After the treatments at 150°C for 80s the contact angle of the PVC was greatly increased from 90.5 to 97.9°. The SEM and AFM reveal that the surface morphology and roughness changes on the PVC surface. XPS and FT-IR results further confirmed an increase of hydrophobic functional groups on the PVC surface. At the optimized froth flotation and subsequent mixing at 150rpm, 100% of PVC was recovered from the remaining plastic mixture with 93.8% purity. The combined technique can provide a simple and effective method for the selective separation of PVC from heavy plastics mixtures to facilitate easy industrial recycling.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PAC coating and mild heat treatment were combined for selective wetting of PVC. </LI> <LI> The combined treatment rearranged the PVC surface and increased its hydrophobicity. </LI> <LI> Optimized froth flotation was crucial for selective separation of the treated PVC. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>