Reversible adsorption of metalworking fluids (MWFs) on Cu-BTC metal organic framework

Metalworking fluids(MWFs) are classified as hazardous substances. Due to the characteristics of the stable oil–water emulsions, it requires more costly and complicate treatment techniques to remove oil from spent MWFs. Metal organic frameworks(MOFs) are a porous network material used to remove contaminants from environment. One of the most prominent of MOFs is HKUST-1 or Cu-BTC. In this study, the Cu-BTCs were prepared by solvothermal method in various conditions and used as absorbent for removing oil micelles in MWF emulsion. The particle size of all synthesized Cu-BTCs ranged from ≈80 to 400 nm. The ability of all synthesized Cu-BTCs to remove oil micelle was greater than 95% in 60 min, while the capacity of GAC was obtained the result for only 6.8%. The maximum adsorption capacity(q _(max)) of oil micelles on Cu-BTCs was 1666.7 mg·g~(-1). The highest removal capacity of oil micelles in MWF emulsion is greater than 99% in 24 h by using Cu-BTCs washed with either butanol or ethanol.     

Gas-bubbled nano zero-valent iron process for high concentration arsenate removal

In this study, batch experiments were performed to investigate a novel process for high concentration arsenate removal in the presence of air and/or CO(2) bubbling. The pretreatment step, CO(2) bubbling at 300 mL/min for 5 min, was taken to adjust the solution pH to an acidic environment, followed by air bubbling at 300 mL/min for 10 min to increase dissolved oxygen in the solution. In the treatment period, the nano-scale zero-valent iron was applied to remove aqueous arsenate of 3000 μg/L, while the treatment system was continuously bubbled by 300 mL/min of air. Such a process resulted in outstanding performance in arsenate removal. Furthermore, in the field groundwater application, the arsenate removal rate for the proposed process was 5 times faster than the rate measured when the system was pretreated by acidic chemical species only.     

Fed-batch optimization of recombinant <Emphasis Type="Italic">α</Emphasis>-amylase production by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> using a modified Markov chain Monte Carlo technique

A modified Markov Chain Monte Carlo (MCMC) searching procedure was developed to search for an optimal set of decision variables and optimal feed rate trajectories for recombinant α-amylase expression by Bacillus subtilis ATCC 6051a. The bacterium also synthesizes proteases as undesirable products in fed-batch culture that need to be minimized. To maximize α-amylase productivity, a 14th-order fed-batch model was optimized by integrating Pontryagin’s maximum principle with the Luedeking-Piret equation. The number of iterations and simulations of the proposed searching procedure were statistically examined for accuracy and acceptability of the results. It can be concluded that the proposed searching procedure increased the parameter selection opportunity near the tail ends of redefined triangular distribution. By applying a modified MCMC searching procedure with 1,500 iterations, the predicted α-amylase productivity was improved by 18% in comparison with near-optimum experimental results. This productivity was 3.5% higher than predicted by conventional MCMC optimization.     

Photocatalytic degradation of benzene,toluene, ethylbenzene,and xylene (BTEX) using transition metal-doped titanium dioxide immobilized on fiberglass cloth

Transition metal (Fe, V and W)-doped TiO₂ was synthesized via the solvothermal technique and immobilized onto fiberglass cloth (FGC) for uses in photocatalytic decomposition of gaseous volatile organic compounds—benzene, toluene, ethylbenzene and xylene (BTEX)—under visible light. Results were compared to that of the standard commercial pure TiO₂ (P25) coated FGC. All doped samples exhibit higher visible light catalytic activity than the pure TiO₂. The V-doped sample shows the highest photocatalytic activity followed by the W- and Fe-doped samples. The UV-Vis diffuse reflectance spectra reveal that the V-doped sample has the highest visible light absorption followed by the W- and Fe-doped samples. The X-ray diffraction (XRD) patterns indicate that all doped samples contain both anatase and rutile phases with the majority (>80%) being anatase. No new peaks associated with dopant oxides can be observed, suggesting that the transition metal (TM) dopants are well mixed into the TiO₂ lattice, or are below the detection limit of the XRD. The X-ray absorption near-edge structure spectra of the Ti K-edge transition indicate that most Ti ions are in a tetravalent state with octahedral coordination, but with increased lattice distortion from Fe- to V- and W-doped samples. Our results show that the TM-doped TiO₂ were successfully synthesized and immobilized onto flexible fiberglass cloth suitable for treatment of gaseous organic pollutants under visible light.     

Visible light-irradiated degradation of alachlor on Fe-TiO<Subscript>2</Subscript> with assistance of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

0.1 Fe/Ti mole ratio of Fe-TiO₂ catalysts were synthesized via solvothermal method and calcined at various temperatures: 300, 400, and 500 °C. The calcined catalysts were characterized by XRD, N₂-adsorption-desorption, UV-DRS, XRF, and Zeta potential and tested for photocatalytic degradation of alachlor under visible light. The calcined catalysts consisted only of anatase phase. The BET specific surface area decreased with the calcination temperatures. The doping Fe ion induced a red shift of absorption capacity from UV to the visible region. The Fe-TiO₂ calcined at 400 °C showed the highest photocatalytic activity on degradation of alachlor with assistance of 30 mM H₂O₂ at pH 3 under visible light irradiation. The degradation fitted well with Langmuir-Hinshelwood model that gave adsorption coefficient and the reaction rate constant of 0.683 L mg⁻¹ and 0.136 mg/L·min, respectively.     

Utilization of mesoporous molecular sieves synthesized from natural source rice husk silica to Chlorinated Volatile Organic Compounds (CVOCs) adsorption

The adsorption of trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride was studied over our synthesized mesoporous material, MCM-41, from rice husk silica source, abbreviated as RH-MCM-41. More than 99% silica for RH-MCM-41 synthesis was extracted from rice husk under refluxing in HBr solution and then calcined at 873 K for 4 hours. RH-MCM-41 possessed surface area around 750-1,100 m²/g with a uniform pore size with an average diameter of 2.95 nm, narrow range of pore distribution and somewhat hexagonal structure, similar to properties of parent MCM-41. The adsorption of CC1₄ to RH-MCM-41 was stronger than that of TCE and PCE. The adsorption capacity of RH-MCM-41 for CVOCs (chlorinated volatile organic compounds) was higher than commercial mordenite and activated carbons.     

Adsorption behavior of NO and CO and their reaction over cobalt on zeolite beta

Adsorption behavior of NO and CO as well as their reaction was investigated on cobalt supported zeolite beta (Co/BEA) prepared by solid-state ion exchange (SSIE) and by impregnation (IMP). By temperature programmed desorption (TPD), two NO desorption peaks at 100 and 260‡C were observed over both SSIE and IMP catalysts with complete desorption after 450‡C. CO desorbed from SSIE catalyst between 50 and 200‡C. In the same temperature interval negligible CO₂ desorption was observed, most likely due to reaction of CO with trace of cobalt oxides. Over IMP catalysts, desorption of CO₂ was found mainly at 500‡C. By comparing CO TPD profiles from physical mixtures of cobalt oxides and HBEA, SSIE catalysts most likely contained cobalt cations in zeolite exchange position while IMP catalysts had cobalt in oxidic forms. The SSIE catalysts were active for NO reduction at 400 and 500‡C with a maximum conversion at 500‡C. However, the activity in the presence of water and oxygen was low. Water might inhibit the reaction by blocking active sites for NO and CO, while oxygen reacted with CO to form carbon dioxide. The activity of SSIE was better than IMP catalyst.     

Effect of Fe<Superscript>3+</Superscript> doping on the performance of TiO<Subscript>2</Subscript> mechanocoated alumina bead photocatalysts

Ferric ion was introduced to the commercial photocatalyst P25 (Degussa) by ultrasonic wet impregnation technique. The concentration of the dopant was varied from 0.0 to 3.0% Fe/Ti ratio. The doped TiO₂ was then loaded to alumina balls using mechanical coating technique and followed by calcination in air at 400, 450, 500 and 550 °C. The fabricated photocatalyst was characterized by X-ray diffraction, N₂ adsorption-desorption isotherms, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, X-ray adsorption near edge structure and photoluminescence spectroscopy. The photocatalytic activity was tested by following the degradation of methylene blue (MB). It was found that the Fe³⁺ doped TiO₂/Al₂O₃ has a combination of anatase and rutile phase and free of iron oxide phases. The optimum calcination temperature is 400 °C with 0.1% Fe³⁺ concentration. The catalyst addresses the entrainment in photocatalytic reactors, eliminating the need for a post filtration process.     

Influence of functional silanes on hydrophobicity of MCM-41 synthesized from rice husk

Mesoporous molecular sieve MCM-41 was synthesized from rice husk and rice husk ash, called RH-MCM-41 and RHA-MCM-41. The sol–gel mixtures were prepared with molar composition of 1.0 SiO₂: 1.1 NaOH: 0.13 CTAB: 0.12 H₂O. After calcination, the polarity of MCM-41 still remained on its surface due to the existence of some silanol groups. In this study, both RH-MCM-41 and RHA-MCM-41 were silylated with two different functional silanes trimethylchlorosilane (TMCS) and phenyldimethylchlorosilane (PDMS) in order to reduce the surface polarity. The efficiency of silylation was determined based on the amount of moisture adsorbed using thermogravimetric analysis (TGA). The structure of silylating agents and silica templates were found to be important parameters affecting the hydrophobic property of the MCM-41 surface. The post-grafting silylation with aliphatic silane can decrease the surface polarity better than that with aromatic silane, probably due to less sterric hindrance effect. Thus, the surface hydrophobicity of MCM-41 can be improved by the silylation of small molecular silane on RH-MCM-41.