Role of Calcination Temperature on Isosorbide Production from Sorbitol Dehydration over the Catalyst Derived from Ce(IV)Sulfate

Isosorbide is a multi-purpose chemical that can be produced from renewable resources.Specifically,it has been investigated as a replacement for toxic bisphenol A(BPA)in the production of polycarbonate(PC).In this study,the synthesis of isosorbide by sorbitol dehydration using a cerium-based catalyst derived from calcined cerium(IV)sulfate(300°C,400°C,450°C,500°C,and 650°C)was investigated.The reaction occurred in a high-pressure reactor containing nitrogen gas.Advanced instrumental techniques were applied to analyze the characteristics of the calcined catalyst.The results showed that the calcined catalysts demonstrated different crystalline structures and sulfate species at different temperatures.However,the acidic properties(strength and amount)of the catalyst did not change with the calcination temperature.The cerium(IV)sulfate calcined at 400°C exhibited the best catalytic performance,achieving the highest isosorbide yield(55.7%)and complete conversion of sorbitol at 180°C,20 bar of N2,and 6 h using CeSO-400.The presence of a sulfate group on the catalyst was the most important factor in determining the catalytic performance of sorbitol dehydration to isosorbide.This work suggests that CeSO-400 catalysts may play an important role in reducing reaction conditions.

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.

Fabrication and photocatalytic activity of TiO2 composite membranes via simultaneous electrospinning and electrospraying process

In present study, a simultaneous electrospinning and electrospraying(SEE) process was employed to produce microclusters of TiO_2 nanoparticles and interlock them in nanofibrous network. The photocatalytic composite membranes(PCMs) were fabricated by electrospraying TiO_2 nanoparticle suspension into microcluster form that dispersed and entrapped within nylon-6 electrospun fiber membrane. Three PCMs membrane with TiO_2 content of 52.0, 83.6,and 91.7 wt.% were successfully fabricated. The membrane consisted of TiO_2 microclusters,ranging in sizes from around 0.3 to 10 μm, distributed uniformly within the nylon-6 nanofibrous network. PCMs photocatalytic activity against Methylene Blue(MB) in aqueous solution showed more than 98% MB removal efficiency after 120 min of photocatalytic oxidation(PCO) for all PCMs. For PCM with the highest TiO_2 content tested for 5 PCO cycles, it was found that most of their TiO_2 content remained incorporated within the nanofibrous structure. The concept of nanoparticles clusters entrapment with SEE fabrication employed here provide a simple and effective method for reducing detachment of nanostructure phase from nanocomposite membrane.

Heterogeneous photocatalytic degradation of diuron on zinc oxide: Influence of surface-dependent adsorption on kinetics,degradation pathway,and toxicity of intermediates

Heterogeneous photocatalytic reaction has been generally applied for degradation of toxic contaminants.Degradations of a compound using the same kind of catalyst that was synthesized differently are commonly found in literature.However,the reported degradation intermediates are normally inconsistent.This issue is especially important for the degradation of toxic compounds because intermediates may be more toxic than their parent compounds and understanding the reason is necessary if appropriate catalysts are to be designed.This work systematically compares the photocatalytic degradation of diuron,a toxic recalcitrant herbicide,on two forms of zinc oxide(ZnO),i.e.,conventional particles with zinc-and oxygen-terminated polar surfaces as the dominating planes,and nanorods with mixed-terminated nonpolar surfaces.Experimental and theoretical results indicate that both the rate of reaction and the degradation pathway depend on the adsorption configuration of diuron onto the surface.Diuron molecules adsorb in different alignments on the two surfaces,contributing to the formation of different degradation intermediates.Both the aliphatic and aromatic sides of diuron adsorb on the polar surfaces simultaneously,leading to an attack by hydroxyl radicals from both ends.On the other hand,on the mixed-terminated surface,only the aliphatic part adsorbs and is degraded.The exposed surface is therefore the key factor controlling the degradation pathway.For diuron degradation on ZnO,a catalyst confined tomixed-terminated surfaces,i.e.,ZnO nanorods,is more desirable,as it avoids the formation of intermediates with potent phytotoxicity and cytogenotoxicity.

Adsorption of single and mixed haloacetonitriles on silica-based porous materials: Mechanisms and effects of porous structures

Adsorption mechanisms and the role of different porous and crystalline structures on the removal of five haloacetonitriles(HANs) over hexagonal mesoporous silica(HMS), titanium substituted mesoporous silica(Ti-HMS), rod-shaped SBA-15 and microporous zeolite Na Y were investigated. In addition, the effect of p H on adsorption mechanism and selective adsorption of five HANs individually and in an equimolar mixed solution were evaluated.The results indicated that the intraparticle diffusion rate constants of the mesoporous adsorbents were higher than that of the microporous Na Y. In single solute, the order of adsorption preference(highest to lowest) was mono-HANs > di-HANs > tri-HAN. However,in mixed solute, the large molecular weight of the tri-HAN and di-HANs are more easily adsorbed than the smaller molecular weight mono-HANs. Except for SBA-15, the order of adsorption capacities in mixed HANs solute was not different compared to that observed for the single HAN solute, which might be caused by the higher accessibility to the active sites due to larger pore size. The ion-dipole electrostatic interaction was likely to be the main adsorption mechanism, and was favored at high p H values due to the high negative surface charge density of the adsorbent. The molecular structure of the HANs and hydrophilic/hydrophobic nature affected the adsorption capacities and their selective adsorption from mixed solutes.

Anaerobic biodegradation of trimethoprim with sulfate as an electron acceptor

Trimethoprim(TMP)is an antibiotic frequently detected in various environments.Microorganisms are the main drivers of emerging antibiotic contaminant degradation in the environment.However,the feasibility and stability of the anaerobic biodegradation of TMP with sulfate as an electron acceptor remain poorly understood.Here,TMP-degrading microbial consortia were successfully enriched from municipal activated sludge(AS)and river sediment(RS)as the initial inoculums.The acclimated consortia were capable of transforming TMP through demethylation,and the hydroxyl-substituted demethylated product(4-desmethyl-TMP)was further degraded.The biodegradation ofTMP followed a 3-parameter sigmoid kinetic model.The potential degraders(Acetobacterium,Desulfovibrio,Desulfbbulbus,and unidentified Peptococcaceae)and fermenters(Lentimicrobium and Petrimonas)were significantly enriched in the acclimated consortia.The AS-and RS-acclimated TMP-degrading consortia had similar core microbiomes.The anaerobic biodegradation ofTMP could be coupled with sulfate respiration,which gives new insights into the antibiotic fate in real environments and provides a new route for the bioremediation of antibiotic-contaminated environments.

Differences in nitrite-oxidizing communities and kinetics in a brackish environment after enrichment at low and high nitrite concentrations

Nitrite accumulation in shrimp ponds can pose serious adverse effects to shrimp production and the environment.This study aims to develop an effective process for the enrichment of ready-to-use nitrite-oxidizing bacteria(NOB)inocula that would be appropriate for nitrite removal in brackish shrimp ponds.To achieve this objective,the effects of nitrite concentrations on NOB communities and nitrite oxidation kinetics in a brackish environment were investigated.Moving-bed biofilm sequencing batch reactors and continuous moving-bed biofilm reactors were used for the enrichment of NOB at various nitrite concentrations,using sediment from brackish shrimp ponds as seed inoculum.The results from NOB population analysis with quantitative polymerase chain reaction(q PCR)show that only Nitrospira were detected in the sediment from the shrimp ponds.After the enrichment,both Nitrospira and Nitrobacter coexisted in the reactors controlling effluent nitrite at 0.1 and 0.5 mg-NO_2^--N/L.On the other hand,in the reactors controlling effluent nitrite at 3,20,and 100 mg-NO_2^--N/L,Nitrobacter outcompeted Nitrospira in many orders of magnitude.The half saturation coefficients(Ks)for nitrite oxidation of the enrichments at low nitrite concentrations(0.1 and 0.5 mg-NO_2^--N/L)were in the range of 0.71–0.98 mg-NO_2^--N/L.In contrast,the Ksvalues of NOB enriched at high nitrite concentrations(3,20,and 100 mg-NO_2^--N/L)were much higher(8.36–12.20 mg-NO_2^--N/L).The results suggest that the selection of nitrite concentrations for the enrichment of NOB inocula can significantly influence NOB populations and kinetics,which could affect the effectiveness of their applications in brackish shrimp ponds.