Catalytic removal of harmful volatile organic compounds by reutilizing zinc rods waste from spent batteries as a palladium catalyst support.

The emission of volatile organic compounds (VOCs) has led to significant deterioration in air quality, making it imperative to ensure that these compounds are removed from emission sources before they are released into the atmosphere. In this context, the present study recycled spent primary batteries to use their zinc rods waste (ZRW) as a palladium catalyst support for the removal of harmful VOCs. To this end, palladium supported on ZRW (Pd/ZRW) catalysts were prepared and tested for the catalytic oxidation of benzene, methylbenzene and 1,2-dimethylbenzene. The physicochemical properties of the Pd/ZRW catalysts were carefully characterized by ICP-OES, BET, SEM, XRD, FE-TEM, XPS, and H2-TPR analyses. The main component of ZRW was identified as ZnO. Consistent with expectations, increases in the loading of Pd from 0.1 to 1.0 wt% in the Pd/ZRW catalysts resulted in enhanced VOCs removal efficiency. The reaction temperature required for the complete oxidation (100% removal efficiency) of methylbenzene and 1,2-dimethylbenzene on the 1.0 wt% Pd/ZRW catalyst was below 340 °C at a gas hourly space velocity of 50,000 h-1. TEM, XPS, and H2-TPR results implied that the enhancement of catalytic activity with the addition of Pd could be attributed to the readily movable surface lattice oxygen as well as the active component (Pd species). Ultimately, ZRW of spent primary batteries appear to show promise as a catalyst support for VOCs removal. This study has introduced a novel strategy for reducing air pollutants by utilizing waste, which promotes the disposal of hazardous solid waste and ensures clean air quality.

In-situ desulfurization using porous Ca-based materials for the oxy-CFB process: A computational study.

Within circulating fluidized bed (CFB) processes, gas and solid behaviors are mutually affected by operating conditions. Therefore, understanding the behaviors of gas and solid materials inside CFB processes is required for designing and operating those processes. In addition, in order to minimize the environmental impact, modeling to reduce pollutants such as SOx emitted from those processes is essential, and simulation reproduction is necessary for optimization, but little is known. In this study, the gas and solid behaviors in a pilot-scale circulating fluidized bed combustor were investigated by using computational particle fluid dynamics (CPFD) numerical simulation based on the multiphase particle-in-cell (MP-PIC) method under oxy-fuel combustion conditions. In particular, the combustion and in-situ desulfurization reactions simultaneously were considered in this CPFD model. Effect of fluidization number (ULS/Umf) was investigated through the comparison of particle circulation rates with regards to the loop seal flux plane and bed height in the standpipe. In addition, the effects of parameters (temperature, Ca/S molar ratio, and particle size distribution), sensitive indicators for the desulfurization efficiency of limestone, were confirmed. Based on the cycle of the thermodynamic equilibrium curve of limestone, it is suggested that direct and indirect desulfurization occur simultaneously under different operating conditions in CFB, creating an environment in which various reactions other than desulfurization can occur. Addition of the reaction equations (i.e., porosity, diffusion) to the established simple model minimizes uncertainty in the results. Furthermore, the model can be utilized to optimize in-situ desulfurization under oxy-CFB operating conditions.

Catalytic ozonation of methylethylketone over porous Mn-Cu/HZSM-5.

The catalytic ozonation of methylethylketone (MEK) was performed at the room temperature (25 °C) using the synthesized Mn and Cu-loaded zeolite (ZSM-5, SiO2/Al2O3 = 80) catalysts. The ZSM-5 zeolite was used as a porous support material due to the large surface area and high capacity for adsorption of volatile organic compounds. Since Mn and Cu-loaded zeolite catalysts were effective for the catalytic ozonation of VOCs such as MEK, according to the loaded concentration of Mn and Cu, there are four types of metal loaded ZSM5 catalysts synthesized [5 wt% Mn/ZSM-5, 5 wt% Cu/ZSM-5, 5 wt% Mn-1 wt% Cu/ZSM-5 (5Mn1CuZSM), and 5 wt% Cu-1 wt% Mn/ZSM-5]. The catalytic efficiency for the removal of MEK and ozonation using the different catalysts was also studied. Based on various experimental analysis processes, the characteristics of the synthesized catalysts were explored and the removal efficiencies of MEK and O3 together with the COx concentration generated from the destruction of MEK and O3 were explored. The results for the decomposition of MEK and O3 at the room temperature indicated that the Mn dominant ZSM-5 catalysts showed better efficiency for the conversion of MEK and O3. The 5 wt% Mn/ZSM-5 outweighed the rest of them for the removal of MEK while the 5Mn1CuZSM showed the best catalytic reactivity for the conversion of O3 and the CO2 selectivity. It was ascertained that during the reaction time of catalyst and reactants of 120 min the Mn dominantly deposited bimetallic catalyst, 5Mn1CuZSM, was determined as the most effective for the removal of MEK and O3 due to the high capability of production of Mn3+ species and more available adsorbed oxygen sites compared to the other catalysts. Finally, the durability measurement for the 5Mn1CuZSM catalyst was performed together with the produced CO and CO2 concentration for 420 min.

Characteristics of deactivation and thermal regeneration of Nb-doped V2O5-WO3/TiO2 catalyst for NH3-SCR reaction.

This study investigated the effect of Nb doping into V2O5-WO3/TiO2 (VWT) catalyst for removing NOxvia the SCR (selective catalytic reduction) by NH3. The experimental results exhibited that Nb can improve the reactivity of the VWT catalyst at low temperatures. The addition of Nb also enhanced the tolerance to SO2 and H2O. The de-NOx efficiency of the V2O5-WO3-Nb2O5/TiO2 (VWNbT) catalyst was increased up to 12% over that of the VWT catalyst at 240 °C when the catalyst was poisoned for 24 h. The prepared catalysts were characterized by FT-IR, XRD, XPS, and N2 physisorption, elemental analysis. The results showed that the ammonium bisulfate (ABS) was less formed in the VWNbT than in the VWT. Moreover, evolved gas analysis was performed to examine the thermal decomposition behavior of the poisoned catalyst, and confirmed that the ABS deposited on the catalyst was sufficiently decomposed between about 300 and 400 °C. In particular, to most effectively recover the characteristics and activity of the catalysts, thermal treatment at a temperature of 400 °C is suitable.

Effective toluene oxidation under ozone over mesoporous MnOx/γ-Al2O3 catalyst prepared by solvent deficient method: Effect of Mn precursors on catalytic activity.

In this study, the role of manganese precursors in mesoporous (meso) MnOx/γ-Al2O3 catalysts was examined systematically for toluene oxidation under ozone at ambient temperature (20 °C). The meso MnOx/γ-Al2O3 catalysts developed with Mn(CH3COO)2, MnCl2, Mn(NO3)2.4H2O and MnSO4 were prepared by an innovative single step solvent-deficient method (SDM); the catalysts were labeled as MnOx/Al2O3(A), MnOx/Al2O3(C), MnOx/Al2O3(N), and MnOx/Al2O3(S), respectively. Among all, MnOx/Al2O3(C) showed superior performance both in toluene removal (95%) as well as ozone decomposition (88%) followed by acetate, nitrate and sulphated precursor MnOx/Al2O3. The superior performance of MnOx/Al2O3(C) in the oxidation of toluene to COx is associated with the ozone decomposition over highly dispersed MnOx in which extremely active oxygen radicals (O2-, O22- and O-) are generated to enhance the oxidation ability of the catalysts greatly. In addition, toluene adsorption over acid support played a vital role in this reaction. Hence, the properties such as optimum Mn3+/Mn4+ ratio, acidic sites, and smaller particle size (≤2 nm) examined by XPS, TPD of NH3, and TEM results are playing vital role in the present study. In summary, the MnOx/Al2O3 (C) catalyst has great potential in environmental applications particularly for the elimination of volatile organic compounds with low loading of manganese developed by SDM.

Controlling the Oxidation State of Pt Single Atoms for Maximizing Catalytic Activity.

Single-atom catalysts (SACs) have emerged as promising materials in heterogeneous catalysis. Previous studies reported controversial results about the relative level in activity for SACs and nanoparticles (NPs). These works have focused on the effect of metal atom arrangement, without considering the oxidation state of the SACs. Here, we immobilized Pt single atoms on defective ceria and controlled the oxidation state of Pt SACs, from highly oxidized (Pt0 : 16.6 at %) to highly metallic states (Pt0 : 83.8 at %). The Pt SACs with controlled oxidation states were then employed for oxidation of CO, CH4 , or NO, and their activities compared with those of Pt NPs. The highly oxidized Pt SACs presented poorer activities than Pt NPs, whereas metallic Pt SACs showed higher activities. The Pt SAC reduced at 300 °C showed the highest activity for all the oxidations. The Pt SACs with controlled oxidation states revealed a crucial missing link between activity and SACs.

Synergistic Effect of Cu/CeO2 and Pt-BaO/CeO2 Catalysts for a Low-Temperature Lean NO x Trap.

A lean NO x trap (LNT) catalyst has been widely used for removing NO x exhaust from lean-burn engines. However, the operation range of LNT has been limited because of the poor activity of LNT catalysts at low temperatures (≤300 °C), especially in urban driving conditions. To increase NO x removal efficiency during lean-rich cycle operation, a Cu/CeO2 (CC) catalyst was added to a Pt-BaO/CeO2 (PBC) catalyst. In comparison to PBC- or CC-only catalysts, the physical mixture of PBC and CC catalysts (PBC + CC) exhibited a significant synergy for both NO x storage and reduction efficiencies. In particular, low-temperature activity below 200 °C was greatly enhanced. A Pt-BaO-Cu/CeO2 (PBCC) catalyst, which was synthesized by depositing Pt and Cu together on a ceria support, showed poorer NO x removal efficiency. The origin of the synergistic effect over PBC + CC was investigated. Under lean conditions, the CC showed much better activity for NO oxidation, allowing for faster NO x storage on PBC. Under rich conditions, H2 was generated in situ on the CC by a water-gas shift reaction then accelerated the reduction of NO x, which had been stored on PBC, with a higher selectivity to N2. This simple modification in the catalyst can provide an important clue to enhance low-temperature activity of the commercial LNT system.

Fully Dispersed Rh Ensemble Catalyst To Enhance Low-Temperature Activity.

Minimizing the use of precious metal catalysts is important in many applications. Single-atom catalysts (SACs) have received much attention because all of the metal atoms can be used for surface reactions. However, SACs cannot catalyze some important reactions that require ensemble sites. Here, Rh catalysts were prepared by treating 2 wt % Rh/CeO2 hydrothermally at 750 °C for 25 h. Nearly 100% dispersion was obtained, but the surface Rh atoms were not isolated (denoted as ENS). They catalyzed the oxidation of C3H6 or C3H8 at low temperatures, but these oxidations did not occur on the Rh SAC. When the simultaneous oxidation of CO, C3H6, and C3H8 was performed, the T20 (temperature at conversion 20%) for CO oxidation increased significantly from 40 °C for sole CO oxidation to 180 °C on SAC due to the competitive adsorption of hydrocarbons. However, T20 increased much less on ENS, from 60 to 100 °C. ENS exhibited superior activity for low-temperature oxidation. During hydrothermal treatment for 25 h, the Rh size initially increased from 2.3 to 6.7 nm then decreased to 0.9 nm. The surface hydroxyl groups formed on the catalyst surface help detach Rh atoms from Rh clusters, while preventing the reaggregation of dispersed Rh atoms into Rh clusters. This fully dispersed catalyst would have maximum atom-efficiency while catalyzing various surface reactions.

Catalytic Pyrolysis of Municipal Plastic Film Wastes Over Nanoporous Al-MCM-41.

A mesoporous material, Al-MCM-41, was applied to the catalytic pyrolysis of municipal plastic film waste (MPFW) to produce large amounts of valuable hydrocarbons. Compared to non-catalytic pyrolysis, the catalytic pyrolysis of MPFW over Al-MCM-41 revealed a lower decomposition temperature and activation energy upon thermogravimetric analysis. Heavy aliphatic hydrocarbons, which are the major products of non-catalytic pyrolysis, were cracked into small hydrocarbons and converted efficiently to aromatic hydrocarbons by catalytic pyrolysis over Al-MCM-41. The activity of catalytic conversion was enhanced by increasing the catalyst to reactant ratio.

Removal of Cu(2+) by biochars derived from green macroalgae.

The by-product char of the fast pyrolysis of a green macroalga Enteromorpha compressa was used to remove copper from an aqueous solution. The surface area and the amount of cation exchange capacity (CEC) were increased by steam activation, resulting in enhanced adsorption capacity. Although chemical activation using a KOH solution increased the pore volume and surface area dramatically, it decreased the adsorption capacity because of activating in the KOH solution and washing decreased CEC. Ion exchange between the Cu ions and cations (Na(+), K(+), Ca(2+), and Mg(2+)) as well as adsorption onto the functional groups on the char surface appeared to be important mechanisms for the removal of Cu. A pseudo-second-order kinetic model and Langmuir isotherm model could interpret the kinetics and equilibrium of the Cu adsorption on the E. compressa char. The maximum amount of Cu adsorption on the char was 137 mg g(-1).

Pyrolysis and catalytic upgrading of Citrus unshiu peel.

Ex situ catalytic pyrolysis of Citrus unshiu (C. unshiu) peel was performed using a tandem µ-reactor-GC/MS consisting of two sequential furnaces. The pyrolyzates of C. unshiu peel, composed mainly of alcohols, ketones and furans produced in the 1st furnace of the reactor, were upgraded to aromatics by the use of catalysts in the 2nd furnace. Compared to wood powder, C. unshiu peel produced larger amounts of aromatics over HZSM-5(23). Among the various catalysts, HZSM-5(23) and HBETA(25) showed high aromatic yields, 6.78 C% and 9.69 C%, respectively. HBETA(25) produced large amounts of undesirable PAHs (3.59 C%). During the sequential catalytic upgrading test, the yield of BTEXs (benzene, toluene, ethylbenzene, xylenes) over HZSM-5(23) was reduced more slowly than that over HBETA(25) because of the slower deactivation of HZSM-5(23), which suggests that HZSM-5(23) is a more stable catalyst than the other catalysts used in this study during the sequential catalytic upgrading of C. unshiu peel pyrolyzates.

Combined chemotherapy and intra-arterial chemotherapy of retinoblastoma.

PURPOSE: Retinoblastoma (RB) is the most common primary malignant intraocular tumor in children. Although systemic chemotherapy has been the primary treatment, intra-arterial chemotherapy (IAC) represents a new treatment option. Here, we performed alternate systemic chemotherapy and IAC and retrospectively reviewed the efficacy and safety of this approach. METHODS: Patients diagnosed with intraocular RB between January 2000 and December 2011 at Severance Children's Hospital, Yonsei University, were reviewed. Before February 2010, the primary treatment for RB was chemotherapy (non-IAC/CTX). Since February 2010, the primary treatment for RB has been IAC (IAC/CTX). External beam radiotherapy or high-dose chemotherapy were used as "last resort" treatments just prior to enucleation at the time of progression or recurrence during primary treatment. Enucleation-free survival (EFS) and progression-free survival were assessed. RESULTS: We examined 19 patients (median age, 11.9 months; range, 1.4 to 75.6 months) with a sum of 25 eyes, of which, 60.0% were at advanced Reese Ellsworth (RE) stages. The enucleation rate was 33.3% at early RE stages and 81.8% at advanced RE stages (P=0.028). At 36 months, EFS was significantly higher in the IAC/CTX group than in the non-IAC/CTX group (100% vs. 40.0%, P=0.016). All 5 patients treated with IAC achieved eye preservation, although most patients were at advanced RE stages (IV-V). CONCLUSION: Despite the limitation of a small sample size, our work shows that an alternative combined approach using IAC and CTX may be safe and effective for eye preservation in advanced RB.

Increasing and worsening late effects in childhood cancer survivors during follow-up.

Recent advances in childhood cancer treatment have increased survival rates to 80%. Two out of three survivors experience late effects (LEs). From a group of 241 survivors previously described, 193 were followed at the long-term follow-up clinic (LTFC) of Severance Hospital in Korea; the presence of LEs was confirmed by oncologists. We reported the change in LEs during 3 yr of follow-up. The median follow-up from diagnosis was 10.4 yr (5.1-26.2 yr). Among 193 survivors, the percentage of patients with at least one LE increased from 63.2% at the initial visit to 75.1% at the most recent visit (P = 0.011). The proportion of patients having multiple LEs and grade 2 or higher LEs increased from the initial visit (P = 0.001 respectively). Forty-eight non-responders to the LTFC were older and had less frequent and severe LEs than responders at initial visit (all P < 0.05). In multivariate analysis, younger age at diagnosis, older age at initial visit, a diagnosis of a brain tumor or lymphoma, and use of radiotherapy were significant risk factors for LEs (all P < 0.05). Adverse changes in LEs were seen among the survivors, regardless of most clinical risk factors. They need to receive comprehensive, long-term follow up.