Heteroatom-doped porous carbon from methyl orange dye wastewater for oxygen reduction

Banana peel-derived porous carbon(BPPC) was prepared from banana peel and used as an adsorbent for methyl orange(MO) wastewater removal. BPPC-MO50 is a N,S-doped BPPC obtained via secondary carbonization. The BPPC-MO50 exhibited a high specific surface area of1774.3 m^2/g. Heteroatom-doped porous carbon(PC) was successfully synthesized from the BPPC absorbed MO at high temperature and used for oxygen reduction. The BPPC-MO50 displayed the highest ORR onset potential among all carbon-based electrocatalysts, i.e., 0.93 V vs.reversible hydrogen electrode(RHE). This is the first report to describe porous carbon-activated materials from agriculture and forestry waste that is used for adsorption of dyes from wastewater via an enhanced heteroatom(N,S) content. These results may contribute to the sustainable development of dye wastewater treatment by transforming saturated PC into an effective material and has potential applications in fuel cells or as energy sources.

Charged modified tight ceramic ultrafiltration membranes for treatment of cationic dye wastewater

Tight ceramic ultrafiltration membranes have been proven to exhibit good rejection performance for reactive dye wastewater at high temperatures because of their high thermal and chemical resistance.However,the application of ceramic membranes for the treatment of cationic dye wastewater is challenging because of their surface charge.In this study,a ceramic membrane is modified by grafting aminosilane(KH-551)to enhance the positive charge of the membrane surface.The rejection performance of the charged modified ceramic membrane toward the methylene blue solution is significantly improved.The modification substance is bonded to the ceramic membrane surface via covalent bonding,which imparts good thermal stability.The modified ceramic membrane exhibits stable separation performance toward the methylene blue solution.Overall,this study provides valuable guidance for the adjustment of the ceramic membrane surface charge for treating industrial cationic dye wastewater.

Efficient decolorization of dye-containing wastewater using mycelial pellets formed of marine-derived Aspergillus niger

In order to improve the efficient decolorization of dye-containing water by biosorbent and understand the biosorption mechanism, the self-immobilization mycelial pellets were prepared using a marine-derived fungus Aspergillus niger ZJUBE-1, and an azo dye, Congo red was chosen as a model dye to investigate batch decolorization efficiency by pellets. The pellets as biosorbent showed strong salt and acid tolerance in biosorption process. The results for dye adsorption showed that the biosorption process fitted well with models of pseudo-second-order kinetic and Langmuir isotherm, with a maximum adsorption capacity of 263.2 mg·g^(-1) mycelium. During 6 batches of continuous decolorization operation, the mycelial pellets could possess efficient decolorization abilities(>98.5%).The appearance of new peak in the UV–Vis spectral result indicated that the decolorization process may also contain biodegradation. The mechanism studies showed that efficient biosorption ability of pellets only relies on the active zone on the surface of the pellet, which can be enhanced by nutrition supplement or be shifted outward by a reculture process.

Intercalation modification of FeOCl and its application in dye wastewater treatment

The textile industry spreads globally with the challenges of its wastewater treatment,especially dyes,which are difficult to degrade.To improve coagulation-flocculation process in dye wastewater treatment,an intercalation process was employed to prepare a new efficient coagulant of lithium borohydride-iron oxychloride(LiBH_(4)_FeOCl) in this study.The layered crystal pristine iron oxychloride(FeOCl) material was prepared by chemical gas phase migration.LiBH4 was introduced into the layers of two dimensional(2 D) FeOCl nanosheets by a simple method of liquid phase insertion.The samples were characterized by a field emitting scanning electron microscopy(SEM),a rotating anode X-ray powder diffractometer(XRD),etc.The cationic dye was employed as the simulated pollutant.A coagulation and decolorization experimental device was built to study the coagulation performance of the new coagulant LiBH_(4)_FeOCl.It is found that the intercalation modified LiBH_(4)_FeOCl exhibits the characteristics of crystal structure,and the layered structure of FeOCl is preserved.LiBH_(4)_FeOCl,as an insoluble inorganic solid coagulant,performs well for dye pollutants of methyl red,basic yellow 1,methylene blue,rhodamine B,ethyl violet and Janus green B.The reaction rate is significantly 68% higher than the current commercial coagulants of Al_(2)(SO_(4))_(3).The mechanism analysis reveals that LiBH_(4)_FeOCl breaks and disperses rapidly in the water environment.Its negatively charged material particles can be electrostatically adsorbed with dye pollutant molecules through electrostatic action.The above collaborative actions of breaking,dispersion and electrostatic adsorption are the main coagulation mechanisms of LiBH_(4)_FeOCl.The solid inorganic coagulant of LiBH4FeOCl provides a competitive alternative for traditional inorganic salts and organic coagulants.

High flux photocatalytic self-cleaning nanosheet C_(3)N_(4) membrane supported by cellulose nanofibers for dye wastewater purification

Hazardous dye substances discharged from the textile and dyestuff industries not only threaten local the surrounding ecosystems but are also hard to degraded.We report the preparation of process for a photocatalytic membrane device that can degrade dye pollution under visible light.This filtration membrane,with a well-organized multilayer structure,simultaneously achieves continuous and flow-through separation of degradation products.Cellulose nanofibers(CNFs)were used as a template for nanosheet C_(3)N_(4)(NS C_(3)N_(4))preparation;the performance for the photocatalytic degradation of dyes improved as the morphology changed from bulking to nanosheet.NS C3N4 was then attached to the surface of a prepared CNF membrane via vacuum filtration.This device exhibited high efficiency(the degradation rates of both Rhodamine B and Methylene blue both reached 96%),high flux(above 160 L·h^(-1)·m^(-2)·bar^(-1))and excellent stability(maintaining steady flux and high separation were maintained after 4 h).This easy-preparation,easy-scale-up,and low-cost process provides a new method of fabricating photocatalytic membrane devices for dye wastewater treatment.

Application of electrode materials and catalysts in electrocatalytic treatment of dye wastewater

The dye industry produces a large amount of hazardous wastewater every day worldwide,which brings potential threaten to the global environment.As an excellent method for removal of water chroma and chemical oxygen demand,electrocatalytic methods are currently widely used in the treatment of dye wastewater.The selection and preparation of electrode materials and electrocatalysts play an important role on the electrocatalytic treatment.The aim of this paper is to introduce the most excellent high-efficiency electrode materials and electrocatalysts in the field of dye wastewater treatment.Many electrode materials such as metal electrode materials,boron-doped diamond anode materials and three-dimensional electrode are introduced in detail.Besides,the mechanism of electrocatalytic oxidation is summarized.The composite treatment of active electrode and electrocatalyst are extensively examined.Finally,the progress of photo-assisted electrocatalytic methods of dye wastewater and the catalysts are described.

Preparation of Chitosan-TiO_2 Composite and Application in the De-coloration of Reactive Dyes Wastewater

Chitosan-TiO2 composite has been prepared by the sol-gel process. Tetrabutyl titanate( TTB) was used as a precursor to obtain nano TiO2 sol,which was then added into acid solution of chitosan to form titania network in the matrix. SEM,TG,and Fourier transform infrared spectroscopy( FTIR) were employed to characterize morphology and structure of the Chitosan-TiO2 composite. The resulting hybrid has potential applications for the adsorption and sonolytic-degradation of organic dyes in wastewater.The result shows that the de-coloring ratio reaches 97. 2% at the optimum conditions with the help of ultrasound.

Treatment of Wastewater with High Conductivity by Pulsed Discharge Plasma

A wastewater treatment system was established by means of pulsed dielectric barrier discharge(DBD). The main advantage of this system is that the wastewater is employed as one of the electrodes for the degradation of rhodamine B, which makes use of the high conductivity and lessenes its negative influence on the discharge process. At the same time, the reactive species like ozone and ultraviolet(UV) light generated by the DBD can be utilized for the treatment of wastewater. The effects of some factors like conductivity, peak pulse voltage, discharge frequency and pH values were investigated. The results show that the combination of these reactive species could enhance the degradation of the dye while the ozone played the most important role in the process. The degradation efficiency was enhanced with the increase of energy supplied. The reduction in the concentration of rhodamine B was much more effective with high solution conductivity;under the highest conductivity condition, the degradation rate could rise to 99%.

Durable and recyclable BiOBr/silk fibroin-cellulose acetate composite film for efficient photodegradation of dyes under visible light irradiation

A stable and recyclable of BiOBr/silk fibroincellulose acetate composite film was prepared by blendingwet phase transformation and in situ precipitate technology.The cellulose acetate film modified by silk fibroin formed a finger-shaped porous structure,which provided a large space for the uniform growth of BiOBr nanosheets and facilitated the shuttle flow of dyes in film.The morphology,phase structure,and optical properties of the composite films were characterized using various techniques,and their photocatalytic performance for dye wastewater was evaluated under visible light irradiation.Results showed that the BiOBr/SF-CA composite film exhibited efficient photocatalytic activity with 99.9%of rhodamine B degradation rate.Moreover,the composite film maintained high catalytic stability because Bi as the active species deposited on the film showed almost no loss.Finally,the possible photocatalytic mechanisms in the BiOBr/SF-CA composite film were speculated through radical-trapping experiments and electron spin resonance testing.

Performance of bioferric-submerged membrane bioreactor for dyeing wastewater treatment

Adding iron salt or iron hydroxide to sludge-mixed liquor in an aeration tank of a conventional activated sludge processes(bioferric process)can simultaneously improve the sludge’s filterability and enhance the system’s treatment capacity.In view of this,Fe(OH)3 was added to a submerged membrane bioreactor(SMBR)to enhance the removal efficiency and to mitigate membrane fouling.Bio-ferric process and SMBR were combined to create a novel process called Bioferric-SMBR.A side-by-side comparison study of Bioferric-SMBR and common SMBR dealing with dyeing wastewater was carried out.Bioferric-SMBR showed potential superiority,which could enhance removal efficien-cy,reduce membrane fouling and improve sludge character-istic.When volumetric loading rate was 25% higher than that of common SMBR,the removal efficiencies of Bioferric-SMBR on COD,dye,and NH_(4)^(+)-N were 1.0%,9.5%,and 5.2%higher than that of common SMBR,respectively.The trans-membrane pressure of Bioferric-SMBR was only 36%of that in common SMBR while its membrane flux was 25% higher than that of common SMBR.The stable running period in Bioferric-SMBR was 2.5 times of that in common SMBR when there was no surplus sludge discharged.The mixed liquor suspended solids concentration of Bioferric-SMBR was higher than that of common SMBR with more diversified kinds of microorganisms such as protozoans and metazoans.The mean particle diameter and specific oxygen uptake rate of Bioferric-SMBR were 3.10 and 1.23 times the common SMBR,respectively.

Poultry keratin based decolorants for dyeing wastewater treatment

One of the challenges in wastewater treatment is the low efficiency in decoloring dyeing wastewater.Chicken feather,as a waste material,has a great potential in decoloring the dyeing wastewater.In this study,a lab synthesized dyeing wastewater prepared with acid blue-A dye was treated with a chicken feather keratin-based composite decolorant KA(keratin agent)using batch decoloration techniques.A modified KA(MKA)was also developed to improve the decoloration efficiency.The decoloration performance of the two decolorants was then evaluated in terms of decoloring rate,at various decolorant dosages,pH,reaction temperature and time.Under optimal conditions,the decoloration rates of the KA and MKA in treating the dyeing wastewater were 91.8%and 94.3%,respectively.IR and TEM results indicated that the KA and MKA decolorants removed the dye stuff from the dyeing wastewater by physical adsorption as well as chemical reactions.

Efficient Fe（Ⅲ）/Fe（Ⅱ） cycling triggered by MoO2 in Fenton reaction for the degradation of dye molecules and the reduction of Cr（Ⅵ）

There is a relatively low efficiency of Fe(Ⅲ)/Fe(Ⅱ) conversion cycle and H2 O2 decomposition(<30%) in conventional Fenton process,which further results in a low production efficiency of ·OH and seriously restricts the application of Fenton.Herein,we report that the commercial MoO2 can be used as the cocatalyst in Fenton process to dramatically accelerate the oxidation of Lissamine rhodamine B(L-RhB),where the efficiency of Fe(Ⅲ)/Fe(Ⅱ) cycling is greatly enhanced in the Fenton reaction meanwhile.And the L-RhB solution could be degraded nearly 100% in 1 min in the MoO2 cocatalytic Fenton system under the optimal reaction condition,which is apparently better than that of the conventional Fenton system(~50%).Different from the conventional Fenton reaction where the ’OH plays an important role in the oxidation process,it shows that 1 O2 contributes most in the MoO2 cocatalytic Fenton reaction.However,it is found that the exposed Mo^4+ active sites on the surface of MoO2 powders can greatly promote the rate-limiting step of Fe^3+/Fe^2+ cycle conversion,thus minimizing the dosage of H2 O2(0.400 mmol/L) and Fe^2+(0.105 mmol/L).Interestingly,the MoO2 cocatalytic Fenton system also exhibits a good ability for reducing Cr(Ⅵ) ions,where the reduction ability for Cr(Ⅵ) reaches almost 100% within 2 h.In short,this work shows a new discovery for M002 cocatalytic advanced oxidation processes(AOPs),which devotes a lot to the practical water remediation application.

Bandgap engineering of tetragonal phase CuFeS_(2)quantum dots via mixed-valence single-atomic Ag decoration for synergistic Cr(VI)reduction and RhB degradation

Bandgap engineering through single-atom site binding on semiconducting photocatalyst can boost the intrinsic activity,selectivity,carrier separation,and electron transport.Here,we report a mixed-valence Ag(0)and Ag(I)single atoms co-decorated semiconducting chalcopyrite quantum dots(Ag/CuFeS_(2)QDs)photocatalyst.It demonstrates efficient photocatalytic performances for specific organic dye(rhodamine B,denoted as RhB)as well as inorganic dye(Cr(VI))removal in water under natural sunlight irradiation.The RhB degradation and Cr(VI)removal efficiencies by Ag/CuFeS_(2)QDs were 3.55 and 6.75 times higher than those of the naked CuFeS_(2)QDs at their optimal pH conditions,respectively.Besides,in a mixture of RhB and Cr(VI)solution under neutral condition,the removal ratio has been elevated from 30.2%to 79.4%for Cr(VI),and from 95.2%to 97.3%for RhB degradation by using Ag/CuFeS_(2)QDs after 2 h sunlight illumination.The intrinsic mechanism for the photocatalytic performance improvement is attributed to the narrow bandgap of the single-atomic Ag(I)anchored CuFeS_(2)QDs,which engineers the electronic structure as well as expands the optical light response range.Significantly,the highly active Ag(0)/CuFeS_(2)and Ag(I)/CuFeS_(2)effectively improve the separation efficiency of the carriers,thus enhancing the photocatalytic performances.This work presents a highly efficient single atom/QDs photocatalyst,constructed through bandgap engineering via mixed-valence single noble metal atoms binding on semiconducting QDs.It paves the way for developing high-efficiency single-atom photocatalysts for complex pollutions removal in dyeing wastewater environment.