Boost activation of peroxymonosulfate by iron doped K_(2-x)Mn_(8)O_(16):Mechanism and properties

Among the numerous transition metal catalysts,manganese-based compounds are considered as promising peroxymonosulfate(PMS)catalysts due to their low cost and environmental friendliness,such as cryptomelane manganese oxide(K_(2-x)Mn_(8)O_(16):abbreviation KMnO).However,the limited catalytic performance of KMnO limits its practical application.In this work,iron-doped KMnO(Fe-KMnO)was prepared by one-step hydrothermal method to optimize its catalytic performance.Compared with KMnO/PMS system,Fe-KMnO/PMS system possessed more excellent removal efficiency of tetracycline(TC).Meanwhile,the Fe-KMnO/PMS system also exhibited good practical application potential and excellent stability.The mechanism of Fe-KMnO activation of PMS was further analyzed in detail.It was found that Fe participated in the redox of high-valent Mn,which promoted the activation of PMS.Moreover,The Fe site as an adsorption site enhanced the TC enrichment ability of the catalyst,reducing the mass transfer resistance and further enhancing the TC removal ability of Fe-KMnO/PMS system.This work not only provides an excellent PMS catalyst,but also offers new insights into the mechanism of PMS activation by bimetallic manganese-based catalysts.

Biochar regulates biogeochemical cycling of iron and chromium in a soil-rice system by stimulating Geobacter and Clostridium

In soil-rice systems,microbial reduction of iron(Fe)has been recognized as a crucial biogeochemical process that regulates Fe and chromium(Cr)translocation;however,the underlying processes are unknown.To investigate the impacts of biochar on the biochemical cycling of Fe and Cr and their toxicity to rice,maize straw biochar was applied at 1%(weight/weight)to a paddy soil spiked with 300 mg kg^(-1)Cr under two phosphorus(P)levels(0 or 90 mg kg^(-1))in a pot experiment.The key microbial groups affecting Fe dissimilatory reduction and their environmental drivers were explored.Biochar inhibited root Cr uptake by 36%,owing to the promoted iron plaque(IP)formation on the rice root surface.Correlation analysis showed that Fe concentration in pore water was strongly linked to the abundances of Geobacter(r=0.81-0.94,P<0.05)and Clostridium(r=0.83-0.95,P<0.05),indicating that Geobacter and Clostridium played essential roles in Fe reduction.Redundancy analysis showed that labile carbon and pore water P concentrations were the key determinants influencing Fe-reducing bacterial abundances,accounting for 42%and 32%of the variation in community composition,respectively.Besides,biochar increased Fe and P concentrations in root cell walls,which retained more Cr.Overall,Cr stress in rice under biochar treatment was relieved through increasing IP formation and altering subcellular distribution.These mechanistic insights had important implications for reducing Cr uptake by rice.

Doping effect of rare earth metal ions Sm^(3+),Nd^(3+)and Ce^(4+)on denitration performance of MnO_(x) catalyst in low temperature NH_(3)-SCR reaction

The MnXO_(x) catalysts(i.e.,MnSmO_(x),MnNdO_(x),MnCeO_(x)) were prepared by reverse co-precipitation method and used for NH_(3)-SCR reaction.It is found that MnCeO_(x) catalyst presents the best low tempe rature catalytic activity(higher than 90% NO_(x) conversion in the te mperature range from 125 to 225℃)and excellent H_(2)O+SO_(2) resistance.In order to explore the reason for this result,the characterization of X-ray diffraction(XRD),Raman spectroscopy,Brunauer-Emmett-Teller(BET),H_(2)-temperature programmed reduction(H_(2)-TPR),NH_(3)-temperature programmed desorption(NH_(3)-TPD),X-ray photoelectron spectroscopy(XPS) and in situ diffuse reflaxions infrared Fourier transformations spectroscopy(DRIFTS) were conducted.The obtained results suggest that MnCeO_(x) catalyst shows the largest amount of acid sites and the best reducibility among these MnXO_(x) catalysts.Besides,Ce^(4+) doping inhibits the crystallization of MnO_(x) catalyst and shows the largest specific surface area.Finally,in situ DRIFTS experiments reveal that NH_(3)-SCR reaction over MnCeO_(x) catalyst follows both Langmuir-Hinshelwood(LH) and Eley-Rideal(E-R) mechanisms,which is through "fast SCR" reaction.

A novel bird-nest-like air superoleophobic/superhydrophilic Cu(OH)2-based composite coating for efficient oil–water separation

An air superoleophobic/superhydrophilic composite coating with a unique structure was fabricated by oxidation and further modification of the copper mesh,and its design principle was clarified.This unique bird-nest-like configuration gives it instant superhydrophilicity due to the high surface roughness and high polar surface free energy components,while air superoleophobicity is caused by its extremely low dispersive surface free energy components.Furthermore,a water-resistance mechanism was proposed whereby a polyelectrolyte plays a critical role in improving the water-resistance of fluorosurfactants.It can separate oil–water mixtures with high efficiency(98.72%)and high flux(25185 L·m−2·h−1),and can be reused.In addition,our composite coating had certain anti-acid,anti-alkali,anti-salt and anti-sand impact performance.More importantly,after being soaked in water for a long time or being exposed to the air for a long time,it still retained ultra-high air oil contact angle and showed excellent stability,which provided the possibility for practical applications.Thus,these findings offer the potential for significant practical applications in managing oily wastewater and marine oil spill incidents.

Elucidating dominant factors of PO43–, Cd2+ and nitrobenzene removal by biochar: A comparative investigation based on distinguishable biochars

Biochars produced from crab shell(CSB),oak sawdust(OB),Jeru salem artichoke tuber(JAB) and sorghum grain(SB) displayed distinguishable adsorption-related characteristics,such as specific surface area(SSA),ash content and acidic oxygen-containing functional groups(AFGs),which linked to the biochar adsorption mechanisms of most pollutants.Herein,PO4^3-,Cd^2+,and nitrobenzene(NB) were employed for adsorption by these biochars to elucidate the dominant factors for the adsorption.Adsorption performance of the three pollutants onto these four biochars varied considerably,as exemplified by the excellent adsorption of PO4^3- and Cd^2+ onto CSB(225.3 and 116.0 mg/g,respectively) as compared with onto the other three biochars(4.2-37.1 mg/g for P043-and 9.7-41.0 mg/g for Cd^2+).OB displayed the best adsorption of NB(72.0 mg/g),followed by SB(39.5 mg/g),JAB(31.1 mg/g),and CSB(23.6 mg/g).The kinetics and isotherm adsorption assessments couple with material characterization suggested that the sorption of selected pollutants on biochars was attributed to the multiple mechanisms involved,including coprecipitation,chemical bonds,cation exchange,physical absorption,and complexation.Further path analysis suggested that AFGs and ash content in biochars were more important than SSA with regards to pollutant removal,especially,with ash playing a crucial role in the removal of Cd2+ and PO43-,and AFGs being mainly re s ponsible for NB adsorption.These findings might offer guidance on the preparation or modification of biochar with a targeted function for pollutant removal through an understanding the dominant factors.