Development, dilemma and potential strategies for the application of nanocatalysts in wastewater catalytic ozonation: A review

With the continuous development of nanomaterials in recent years,the application of nanocatalysts in catalytic ozone oxidation has attracted more and more researchers’attention due to their excellent catalytic properties.In this review,we systematically summarized the current research status of nanocatalysts mainly involving material categories,mechanisms and catalytic efficiency.Based on summary and analysis,we found most of the reported nanocatalysts were in the stage of laboratory research,which was caused by the nanocatalysts defects such as easy aggregation,difficult separation,and easy leakage.These defects might result in severe resource waste,economic loss and potentially adverse effects imposed on the ecosystem and human health.Aiming at solving these defects,we further analyzed the reasons and the existing reports,and revealed that coupling nano-catalyst and membrane,supported nanocatalysts and magnetic nanocatalysts had promising potential in solving these problems and promoting the actual application of nanocatalysts in wastewater treatment.Furthermore,the advantages,shortages and our perspectives of these methods are summarized and discussed.

Inhibition character of crotonaldehyde manufacture wastewater on biological acidification

This work aims to investigate the inhibitory effect of crotonaldehyde manufacture wastewater(CMW)on biological acidification.To reveal the inhibitory effect of wastewater to the anaerobic granular sludge(AnGS),variations of the specific acidogenic activity(SAA)and activities of key enzymes were investigated.The results indicated that the dosage of CMW causing a 50%effect concentration(EC50)on the activity of total volatile fatty acids(TVFA)production was 380 mg COD/g VSS.The inhibitory effect of individual toxicants in CMW on the activity of TVFA production were in the order of crotonaldehyde>ethyl sorbate>(E,E)-2,4-hexadienal,and their inhibitory degrees on individual VFA productions were acetic acid(Ac)>n-butyric acid(n-Bu),which could correspond to the variations in the activities of acetate kinase(AK)and butyrate kinase(BK).Furthermore,the combined effect of three toxicants on the activity of TVFA production was significantly higher than that of any individual toxicant,and the contribution of the relative toxicity to CMW was 77.27%.Additionally,the biodegradation products of the main toxicants indicated that the removal of crotonaldehyde and(E,E)-2,4-hexadienal was primarily due to the hydrogenation of alkene and aldehyde and the oxidation of aldehyde.Nevertheless,the removal of ethyl sorbate was primarily based on adsorption.In conclusion,biological acidification has a limited ability to treatment CMW,therefore,a further pretreatment technology should be used to remove the main toxicant of wastewater.

Amorphous molybdenum sulfide mediated EDTA with multiple active sites to boost heavy metal ions removal

The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment.In this study,amorphous molybdenum sulfide composites(EDTA-MoSx(x=2,3))were fabricated via a facile hydrothermal method mediated by EDTA,which was applied to heavy metal ions(Cu^(2+),Cd^(2+),Pb^(2+),Zn^(2+)and Ni^(2+))removal from aqueous solutions.A case study for Cu^(2+)ions showed that the adsorption capacity of EDTA-MoSx(x=2,3)was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L.Adsorption mechanisms of different sulfide groups and—COOH of EDTA-MoSx(x=2,3)were verified systematically via a series of experiments,characterizations,and density functional theory(DFT)calculations.Both bridging S_(2)^(2-)and—COOH covalently bonded with Cu^(2+)ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx(x=2,3).This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.

A magnetic-void-porous MnFe_(2)O_(4)/carbon microspheres nano-catalyst for catalytic ozonation:Preparation,performance and mechanism

Wastewater treatment is essential to guarantee human health and ecological security.Catalytic ozonation with nanocatalysts is a widely studied and efficient treatment technology.However,this method has always been limited by nanocatalysts disadvantages such as easily loss,difficult to separate and reuse,and catalytic ability decay caused by aggregation,which could cause severe resources waste and potential risk to human health and ecosystem.To remedy these challenges,a magnetic-void-porous MnFe_(2)O_(4)/carbon microsphere shell nanocatalyst(CMS-MnFe_(2)O_(4))was successfully synthesized using renewable natural microalgae.The separation test showed CMS-MnFe_(2)O_(4) was rapidly separated within 2 min under an external magnetic field.In catalytic ozonation of oxalic acid(OA),CMS-MnFe_(2)O_(4) showed efficient and stable catalytic efficiency,reaching a maximum total organic carbon removal efficiency of 96.59% and maintained a 93.88% efficiency after 4 cycles.The stable catalytic efficiency was due to the supporting effects of the carbon microsphere shell,which significantly enhanced CMS-MnFe_(2)O_(4) chemical stability and reduced the metal ions leaching to 10-20% of MnFe_(2)O_(4) through electron transfer.To explore the catalytic mechanism,radical experiments were conducted and a new degradation pathway of OA involving superoxide anions rather than hydroxyl radicals was proposed.Consequently,this study suggests that an efficient,recyclable,stable,and durable catalyst for catalytic ozonation could be prepared.