Ethyl thiosemicarbazide intercalated organophilic calcined hydrotalcite as a potential sorbent for the removal of uranium(VI) and thorium(IV) ions from aqueous solutions

This work was conducted to determine the practicability of using a new adsorbent 4-ethyl thiosemicarbazide intercalated,organophilic calcined hydrotalcite(ETSC-OHTC) for the removal of uranium(U(VI)),and thorium(Th(IV)) from water and wastewater.The FTIR analysis helped in realizing the involvement of nitrogen and sulphur atoms of ETSC in binding the metal ions through complex formation.Parameters like adsorbent dosage,solution pH,initial metal ions concentration,contact time and ionic strength,that influence adsorption phenomenon,were studied.The optimum pH for maximum adsorption of U(VI) and Th(IV) was found to be in the range 4.0-6.0.The contact time required for reaching equilibrium was 4 hr.The pseudo second-order kinetic model was the best fit to represent the kinetic data.Analysis of the equilibrium adsorption data using Langmuir,Freundlich and Sips models showed that the Freundlich model was well suited to describe the metal ions adsorption.The K F values were 25.43 and 29.11mg/g for U(VI) and Th(IV),respectively,at 30°C.The adsorbent can be regenerated effectively from U(VI) and Th(IV) loaded ones using 0.01mol/L HCl.The new adsorbent was quite stable for many cycles,without much reduction in its adsorption capacity towards the metals.     

Influences of perfluorooctanoic acid on the aggregation of multi-walled carbon nanotubes

The aggregation of multi-walled carbon nanotubes (MWCNTs) in the aqueous phase not only inhibits their extensive utilization in various aspects but also dominates their environmental fate and transport.The role of surfactants at low concentration in the aggregation of MWCNTs has been studied,however the effect of perfluorinated surfactants at low concentration is uncertain.To understand this interfacial phenomenon,the influences of perfluorooctanoic acid (PFOA),and sodium dodecyl sulfate (SDS) as a control,on MWCNT aggregation in the aqueous phase were examined by the UV absorbency method.Influences of pH and cationic species on the critical coagulation concentration (CCC) value were evaluated.The CCC values were dependent on the concentration of PFOA,however a pronounced effect of SDS concentration on the CCC values was not observed.The CCC values of the MWCNTs were 51.6 mmol/L in NaCl and 0.28 mmol/L in CaCl 2 solutions,which suggested pronounced differences in the effects of Na+ and Ca2+ ions on the aggregation of the MWCNTs.The presence of both PFOA and SDS significantly decreased the CCC values of the MWCNTs in NaCl solution.The aggregation of the MWCNTs took place under acidic conditions and was not notably altered under neutral and alkaline conditions due to the electrostatic repulsion of deprotonated functional groups on the surface of the MWCNTs.     

Pb(II) removal from water using Fe-coated bamboo charcoal with the assistance of microwaves

Bamboo charcoal(BC) was used as starting material to prepare iron-modified bamboo charcoal(Fe-MBC) by its impregnation in FeCl 3 and HNO 3 solutions simultaneously,followed by microwave heating.The material can be used as an adsorbent for Pb(Ⅱ) contaminants removal in water.The composites were prepared with Fe molar concentration of 0.5,1.0 and 2.0 mol/L and characterized by means of N 2 adsorption-desorption isotherms,X-ray diffraction spectroscopy(XRD),scanning electron microscopy coupled with energy dispersive X-ray spectrometry(SEM-EDS),Fourier transform infrared(FT-IR) and point of zero charge(pH pzc) measurements.Nitrogen adsorption analyses showed that the BET specific surface area and total pore volume increased with iron impregnation.The adsorbent with Fe molar concentration of 2 mol/L(2Fe-MBC) exhibited the highest surface area and produced the best pore structure.The Pb(Ⅱ) adsorption process of 2Fe-MBC and BC were evaluated in batch experiments and 2Fe-MBC showed an excellent adsorption capability for removal Pb(Ⅱ).The adsorption of Pb(Ⅱ) strongly depended on solution pH,with maximum values at pH 5.0.The ionic strength had a significant effect on the adsorption at pH < 6.0.The adsorption isotherms followed the Langmuir isotherm model well,and the maximum adsorption capacity for Pb(Ⅱ) was 200.38 mg/g for 2Fe-MBC.The adsorption processes were well fitted by a pseudo second-order kinetic model.Thermodynamic parameters showed that the adsorption of Pb(Ⅱ) onto Fe-MBC was feasible,spontaneous,and exothermic under the studied conditions,and the ion exchange mechanism played an significant role.These results have important implications for the design of low-cost and effective adsorbents in the removal of Pb(Ⅱ) from wastewater.     

Competitive sorption between 17α-ethinyl estradiol and bisphenol A/4-n-nonylphenol by soils

The sorption of 17α-ethinyl estradiol(EE2),bisphenol A(BPA),and 4-n-nonylphenol(NP) in single systems and the sorption of EE2 with different initial aqueous concentrations of BPA or NP were examined using three soils.Results showed that all sorption isotherms were nonlinear and fit the Freundlich model.The degree of nonlinearity was in the order BPA(0.537-0.686) > EE2(0.705-0.858) > NP(0.875-0.0.951) in single systems.The isotherm linearity index of EE2 sorption calculated by the Freundlich model for Loam,Silt Loam and Silt increased from 0.758,0.705 and 0.858,to 0.889,0.910 and 0.969,respectively,when BPA concentration increased from 0 to 1000 μg/L,but the effect of NP was comparably minimal.Additionally,EE2 significantly suppressed the sorption of BPA,but insignificantly suppressed that of NP.These findings can be attributed to the difference of sorption affinity of EE2,NP and BPA on the hard carbon(e.g.,black carbon) of soil organic matter that dominated the sorption in the low equilibrium aqueous concentration range of endocrine-disrupting chemicals(EDCs).Competitive sorption among EDCs presents new challenges for predicting the transport and fate of EDCs under the influence of co-solutes.     

Differences in rheological and fractal properties of conditioned and raw sewage sludge

Rheological tests for raw and conditioned activated sludge(AS) or anaerobic digested sludge(ADS) show that power-law relationships can be used to describe the evolution of several rheological parameters,i.e.,limiting viscosity(η∞),yield stress(τy),cohesion energy of the sludge network(Ec),and storage modulus(G’),with total suspended solid(TSS) content in raw and conditioned sludge.A gel-like structure that behaves similar to weak-link flocs/aggregates was observed in AS and ADS.As derived from the double-logarithmic plots of G’-TSS content,the mass fractal dimensions of the raw and conditioned AS or ADS flocs/aggregates were 2.70 and 2.53 or 2.85 and 2.79,respectively.The rheological tests also indicate that both polymer conditioning and increased TSS content led to improved elastic behavior,cohesion energy,and yield stress of the sludge network,as well as expanded the corresponding linear viscoelastic range.The porosity of AS or ADS flocs/aggregates will be improved by polymer conditioning.     

Adsorption of 2-mercaptobenzothiazole from aqueous solution by organo-bentonite

The adsorption behavior of 2-mercaptobenzothiazole onto organo-bentonite was investigated.Natural bentonite from Gaozhou in Guangdong Province,China was collected.Organo-bentonite was prepared by intercalation of cetyltrimethyl ammonium bromide into the natural bentonite.The physicochemical properties of the prepared organo-bentonite were characterized by X-ray diffraction,N2 adsorption-desorption isotherm and Fourier transform infrared spectroscopy.The results showed that montmorillonite is the main component of the natural bentonite.The basal spacing of the natural bentonite is 1.47 nm,which increased to 1.98 nm on intercalation with cetyltrimethyl ammonium bromide.Moreover,both the surface area and pore volume increased with intercalation.Clear CH2 stretching(3000-2800 cm-1) and scissoring(1480-1450 cm-1) modes of the intercalated surfactants were observed for organobentonite.Compared with the pseudo first-order kinetic model,the pseudo second-order kinetic model is more suitable to describe the adsorption kinetics of 2-mercaptobenzothiazole onto organo-bentonite.The adsorption capacity of 2-mercaptobenzothiazole onto organo-bentonite increased with increasing initial concentration of 2-mercaptobenzothiazole,but decreased with increasing adsorbent dosage.The adsorption isotherm of 2-mercaptobenzothiazole onto organo-bentonite fits well with the Langmuir model.The maximum adsorption capacity of organo-bentonite for 2-mercaptobenzothiazole was 33.61 mg/g,indicating that organo-bentonite is a promising adsorbent for 2-mercaptobenzothiazole.     

Effect of ammonium on nitrous oxide emission during denitrification with different electron donors

Nitrous oxide(N2O) emission during denitrification is receiving intensive attention due to its high potential to cause greenhouse effects.In this study,denitrifiers were acclimated in sequencing batch reactors with methanol or acetate as the electron donor and nitrate as the electron acceptor.The effects of ammonium on N2O emission were examined in batch experiments with various electron donors.With the addition of ammonium,N2O emission increased under all the examined conditions compared to experiments without ammonium addition.With different electron donors,the highest ratio of N2O emission to the removed oxidized nitrogen was 0.70% for methanol,5.34% for acetate,and 34.79% for polyhydroxybutyrate.     

Biodegradation by bioaugmentation of dairy wastewater by fungal consortium on a bioreactor lab-scale and on a pilot-scale

A fungal consortium including Aspergillus niger, Mucor hiemalis and Galactomyces geotrichum was tested for the treatment of dairy wastewater. The bio-augmentation method was tested at lab-scale (4 L), at pilot scale (110 L) and at an industrial scale in Wastewater Treatment Plants (WWTP). The positive impact of fungal addition was confirmed when fungi was beforehand accelerated by pre-culture on whey (5 g/L lactose) or on the dairy effluent. Indeed, chemical oxygen demand (COD) removal yields increased from 55% to 75% for model medium, diluted milk. While after inoculation of an industrial biological tank from a dairy factory with the fungal consortium accelerated by pre-cultivation in a 1000 L pilot plant, the outlet COD values decreased from values above the standard one (100 mg/L) to values in the range of 50-70 mg/L. In addition, there was a clear impact of fungal addition on the ’hard’ or non-biodegradable COD owing to the significant reduction of the increase of the COD on BOD 5 ratio between the inlet and the outlet of the biological tank of WWTP. It was in the range of 451%-1111% before adding fungal consortium, and in the range of 257%-153% after bio-augmentation with fungi. An inoculated bioreactor with fungal consortium was developed at lab-scale and demonstrated successfully at pilot scale in WWTP.     

Removal of Cd2+ from water by Friedel’s salt (FS: 3CaO.Al2O3·CaCl2·10H2O): Sorption characteristics and mechanisms

The development of low-cost and efficient new mineral adsorbents has been a hot topic in recent years. In this study, Friedel’s salt (FS:3CaO·A12O3 ·CaCl2 ·10H2O), a hexagonal layered inorganic absorbent, was synthesized to remove Cd2+ from water. The adsorption process was simulated by Langmuir and Freundlich models. The adsorption mechanism was further analyzed with TEM, XRD, FT-IR analysis and monitoring of metal cations released and solution pH variation. The results indicated the adsorbent FS had an outstanding ability for Cd(Ⅱ) adsorption. The maximum adsorption capacity of the FS for Cd(Ⅱ) removal can reach up to 671.14 mg/g. The nearly equal numbers of Cd2+ adsorbed and Ca2+ released demonstrated that ion-exchange (both surface and inner) of the FS for Cd(Ⅱ) played an important role during the adsorption process. Furthermore, the surface of the FS after adsorption was microscopically disintegrated while the inner lamellar structure was almost unchanged. The behavior of Cd(Ⅱ) adsorption by FS was significantly affected by surface reactions. The mechanisms of Cd2+ adsorption by the FS mainly included surface complexation and surface precipitation. In the present study, the adsorption process was fitted better by the Langmuir isotherm model (R2 = 0.9999) than the Freundlich isotherm model (R2 = 0.8122). Finally, due to the high capacity for ion-exchange on the FS surface, FS is a promising layered inorganic adsorbent for the removal of Cd(Ⅱ) from water.     

Decrease of NH4+-N by bacterioplankton accelerated the removal of cyanobacterial blooms in aerated aquatic ecosystem

We used aerated systems to assess the influence of the bacterioplankton community on cyanobacterial blooms in algae/post-bloom of Lake Taihu, China. Bacterioplankton community diversity was evaluated by polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE) fingerprinting. Chemical analysis and nitrogen dynamic changes illustrated that NH4+-N was nitrified to NO2-N and NO3-N by bacterioplankton. Finally, NH4+-N was exhausted and NO3-N was denitrified to NO2-N, while the accumulation of NO2-N indicated that bacterioplankton with completely aerobic denitrification ability were lacking in the water samples collected from Lake Taihu. We suggested that adding completely aerobic denitrification bacteria(to denitrify NO2-N to N2)would improve the water quality. PCR-DGGE and sequencing results showed that more than 1/3 of the bacterial species were associated with the removal of nitrogen, and Acidovorax temperans was the dominant one. PCR-DGGE, variation of nitrogen, removal efciencies of chlorophyll-a and canonical correspondence analysis indicated that the bacterioplankton significantly influenced the physiological and biochemical changes of cyanobacteria. Additionally, the unweighted pair-group method with arithmetic means revealed there was no obvious harm to the microecosystem from aeration. The present study demonstrated that bacterioplankton can play crucial roles in aerated ecosystems, which could control the impact of cyanobacterial blooms in eutrophicated fresh water systems.