Decolorization Of Acid Orange Research Articles

Decolorization of acid orange 7 in moving bed biofilm reactor packed with polyhydroxyalkanoate/activated carbon

Moving bed biofilm reactor (MBBR) using various carrier medium has been widely employed in wastewater treatment. This study aimed to investigate the feasibility of polyhydroxyalkanoate (PHA) and activated carbon (AC) composite (PHA/AC) as biofilm carrier to enhance MBBR treatment of azo dye acid orange 7 (AO7). Each PHA/AC carrier had a height of 0.40 cm and a cylindrical diameter of 1.25 cm. The biofilm on PHA/AC carrier was characterized using microscopic and chemical analysis. AO7 decolorization efficiency and kinetics were evaluated. The incorporation of AC in PHA was found to promote biofilm growth. Mature biofilm of 2075 ± 79.30 μm was successfully formed on PHA/AC carrier. Compared to a control reactor, the MBBR with 5 % (v/v) PHA/AC exhibited improved decolorization, with decolorization efficiency and first-order rate constant, kAO7, increasing from 78.2 % and 9.90 × 10−4 min−1 to 95.0 % and 1.70 × 10−3 min−1, respectively. The enhancement of decolorization in MBBR was attributed to the presence of anoxic zone within the biofilm that favored the azo bond cleavage. Batch studies on the effects of suspended activated sludge (AS) and biofilm amounts showed an additive effect on decolorization efficiency when combined. The combined suspended AS and biofilm also resulted a 3–4 folds increase in kAO7 value compared to AS alone. The results indicate that PHA/AC was an effective carrier and its biofilm exhibited high decolorizing ability for AO7. The enhancement provided by the PHA/AC biofilm makes it advantageous for developing efficient and environmentally-friendly wastewater treatment systems with compact design and minimal sludge production.

Microbial communities drive flux of acid orange 7 and crystal violet dyes in water-sediment system

Unchecked dye effluent discharge poses escalating environmental and economic concerns, especially in developing nations. While dyes are well-recognized water pollutants, the mechanisms of their environmental spread are least understood. Therefore, the present study examines the partitioning of Acid Orange 7 (AO7) and Crystal Violet (CV) dyes using water-sediment microcosms and reports that native microbes significantly affect AO7 decolorization and transfer. Both dyes transition from infused to pristine matrices, reaching equilibrium in a fortnight. While microbes influence CV partitioning, their role in decolorization is minimal, emphasizing their varied impact on the environmental fate of dyes. Metagenomic analyses reveal contrasting microbial composition between control and AO7-infused samples. Control water samples displayed a dominance of Proteobacteria (62%), Firmicutes (24%), and Bacteroidetes (9%). However, AO7 exposure led to Proteobacteria reducing to 57% and Bacteroidetes to 3%, with Firmicutes increasing to 34%. Sediment samples, primarily comprising Firmicutes (47%) and Proteobacteria (39%), shifted post-AO7 exposure: Proteobacteria increased to 53%, and Firmicutes dropped to 38%. At the genus level, water samples dominated by Niveispirillum (34%) declined after AO7 exposure, while Bacillus and Pseudomonas increased. Notably, Serratia and Sphingomonas, known for azo dye degradation, rose post-exposure, hinting at their role in AO7 decolorization. Conversely, sediment samples showed a decrease in the growth of Bacillus and an increase in that of Pseudomonas and Serratia. These findings emphasize the significant role of microbial communities in determining the environmental fate of dyes, providing insights on its environmental implications and management.

Low salinity enhances azo dyes degradation in aerobic granular sludge systems: Performance and mechanism analysis

The biodegradation performance of azo dyes can be enhanced under low salinity conditions, but the internal biodegradation mechanism is still unclear. Aerobic granular sludge (AGS), a salt-tolerant biological wastewater treatment technology, was used in this study to explore the enhancement mechanism of acid orange 7 (AO7) degradation at low salinity level (1.0 %). Results indicated that the AGS structure and reactor performance were almost unaffected by different AO7 concentrations (5–10 mg/L). Compared with salt-free conditions, the AO7 removal efficiency was elevated by 9.9 %–19.0 % at 1.0 % salinity level, owing to the enrichment of AO7 decolorizing bacteria (e.g. Acinetobacter) and functional enzymes (e.g. FMN-dependent azoreductase). The up-regulated genes involving in the key metabolic functions (e.g. carbon metabolism and oxidative phosphorylation) promoted the electron and energy production, thereby facilitating the AO7 decolorization and degradation. These results aid understanding of the enhancement mechanism of AO7 biodegradation under low salinity conditions from macroscopic and microscopic perspectives.

Facile synthesis of N-rich carbon nanosheets derived from antibiotic mycelial dregs as efficient catalysts for peroxymonosulfate activation

Nitrogen-rich carbon nanosheets using hazardous waste penicillin mycelial dregs (PMD) as the sole precursor were successfully synthesized amid molten salt-assisted pyrolysis and applied as catalysts for peroxymonosulfate (PMS) activation to degrade acid orange 7 (AO7). The structural properties and the associated catalytic performances of carbon nanosheets were precisely regulated by molten salt (NaCl/KCl) mass ratios and pyrolysis temperatures. Carbon nanosheets prepared at a molten salt ratio of 6 and a pyrolysis temperature of 800 °C possessed an optimized catalytic performance, achieving both high effective and efficient decolorization of AO7 than activated carbon catalysts. It was likely attributed to the combination of high graphitic N content and defective carbon structures from nanosheets through quantitative structure-activity relationships analysis. Both radical and non-radical pathways were recognized to be responsible for AO7 degradation, while surface-bound radicals generated from catalyst surface-PMS complexes in non-radical pathways were the main reactive oxygen species. This work offers a green and facile method to prepare high graphitic N content and defect-rich carbon nanosheets from nitrogen-rich biowastes, highlighting its promising catalytic properties for environmental remediation, synchronously expanding the means of resourceful and harmless treatment of PMD to improve the sustainability of antibiotic pharmaceutical production.

Visible light-driven degradation of Acid Orange 7 by light modulation techniques

The impact of light modulation on the decolorization of Acid Orange 7 (AO7) in aqueous solution was examined in this paper. A fixed bed batch photocatalytic reactor with a flat plate geometry, irradiated by 240 white-light LEDs, was used. A successful transfer of visible active photocatalyst (N-TiO2) in powder form on a polystyrene (PS) transparent plate was realized. The structured photocatalyst was characterized through SEM–EDX, Raman and UV-DRS analyses, evidencing the formation of a coating of N-TiO2 in the anatase phase, with a band-gap energy of 2.5 eV, and almost uniform distribution on the PS surface. Different LED dimming techniques, with fixed and variable duty-cycle values, were tested, and four types of light modulation were compared: fixed duty cycle (constant irradiation), sinusoidal variable duty cycle (sinusoidal variable irradiation), triangular variable duty cycle (triangular variable irradiation), and square wave variable duty cycle (square wave variable irradiation). The resulting responsiveness/efficiency of the LED versus the current intensity was evaluated, and the stability of the photocatalyst activity and the influence of optimized irradiation waveforms were examined in the decolorization of 400 mL of 10 ppm AO7 solution. The sinusoidal modulation, with current between 50 and 100 mA and 10 s as the period, shows the highest value of the apparent pseudo-first-order kinetic constant, resulting equal to 0.0044 min−1, at parity of total transmitted photons. An energy saving with the application of sinusoidal irradiation is highlighted with respect to the literature.Graphical

Activation of peroxymonosulfate by pyrophosphate for the degradation of AO7 at neutral pH.

In the present study, pyrophosphate (PP) was used to activate peroxymonosulfate (PMS) for acid orange 7 (AO7) removal under neutral pH conditions. The removal rate of AO7 (20 mg/L) was 84% within the reaction time with a rate constant value of 0.0165 min-1 under optimum conditions. Additionally, the effects of the concentrations of PMS and PP in solutions with various pH values and the coexisting inorganic anions on AO7 removal were measured. In addition, the performance of phosphate (P(V)) on PMS activation was compared with that of phosphite (P(III)) species. In contrast to P(III), the concentration of P(V) showed a positive correlation with the efficiency of AO7 decolorization. PMS activation in different types of buffer solutions was also examined, and the results indicated that the decolorization efficiency of AO7 induced by PP addition, and the buffer solution also contributed to PMS self-decomposition. Singlet oxygen (1O2) might be the primary reactive oxygen species (ROS) in the PP/PMS system in which AO7 is decolorized at an initial pH of 7.06, as indicated by quenching experiments and electron spin resonance (ESR) tests. Therefore, PP/PMS systems may be promising technologies for removing organic contaminants, particularly for PP-rich electroplating wastewater.

Co-Enzymes based nanoflowers incorporated-magnetic carbon nanotubes: A new generation nanocatalyst for superior removal of cationic and anionic dyes with great repeated use

Synthetic dyes leading to substantial discharge in various industrial areas such as textile, plastics, food, and cosmetics, have growingly threatened all livings. Although enzymes have been used for dye degradation, weak stability against changes in reaction environment, lack of reusability and high cost have strictly limited their use. Herein, we have developed co-enzymes nanoflowers incorporated-magnetic carbon nanotube nanocomposite as a novel and efficient nanocatalyst for superior degradation of malachite green (MG) and acid orange 7 (AO7) as model cationic and anionic dyes with excellent cyclic use. The HRP-Lac NF@mCNT nanocomposite (NC) containing horseradish peroxidase–laccase nanoflower (HRP-Lac NF) and iron oxide nanoparticles (Fe 3 O 4 NPs) decorated magnetic carbon nanotube (mCNT) was systematically employed in dye degradation as functions of pH, reaction time, dye type and reusability. This HRP-Lac NF@mCNT nanocomposite acted as one malfunctional nanoplatform since both HRP and Lac enzymes were used for rapid and efficient dye removal, Fe 3 O 4 NPs provided cyclic use and omitting the centrifugation step, and CNT functioned as a unique platform for NFs and Fe 3 O 4 NPs deposition. We demonstrated that HRP-Lac NF@mCNT NC induced ∼ 90 % MG and ∼ 85% AO7 decolorization in 20 min at pH 7.4 while it almost completely decolorized MG and AO7 in 60 min. In addition, ∼ 95% MG and ∼ 85% AO7 decolorization were accomplished even after 16 cycling use of HRP-Lac NF@mCNT NC. We claim that HRP-Lac NF@mCNT NC induced dye decolorization with dual mechanisms, enzymatic degradation, and physical adsorption. • Preparation of horseradish peroxidase–laccase co-enzymes nanoflower incorporated-magnetic carbon nanotubes. • Rapid and efficient dye degradation against a cationic and an anionic dye. • Magnetic property for repeated use.

Synthesis of magnetic hydrochar from Fenton sludge and sewage sludge for enhanced anaerobic decolorization of azo dye AO7

A novel magnetic hydrochar synthesized from Fenton sludge (FS) and sewage sludge (SS) was employed in the anaerobic decolorization of acid orange 7 (AO7). The stable presence of Fe3O4 in magnetic hydrochar was confirmed by physicochemical characterization. The degradation efficiency of AO7 in the anaerobic system with the addition of hydrochar prepared in an optimal proportion (SS:FS=1:3, named as HC-1:3) could reach 98.55%, which was 1.91 times higher than the control system. Particularly, superior electrical conductivity, electron transport system activity and azo reductase activity of the sludge in anaerobic system with HC-1:3 were achieved. The redox of Fe(Ⅲ)/Fe(Ⅱ) in anaerobic system was realized by dissimilatory iron-reducing bacteria enriched with HC-1:3. According to the six-cycle batch experiments and 120-day continuous-flow UASB experiments, the addition of HC-1:3 into the anaerobic system facilitated the diversity of microbiological community and increased the ecological stability of anaerobic system. The possible electron transfer mechanism involving in the magnetic hydrochar-based anaerobic system for AO7 removal was speculated preliminarily. The as-prepared magnetic hydrochar not only showed a promising future in anaerobic system for recalcitrant contaminants degradation, but also provided a new approach for the resource utilization of FS and SS.

Performance of Meyerozyma caribbica as a novel manganese peroxidase-producing yeast inhabiting wood-feeding termite gut symbionts for azo dye decolorization and detoxification

For hazardous toxic pollutants such as textile wastewater and azo dyes, microbial-based and peroxidase-assisted remediation represents a highly promising and environmentally friendly alternative. Under this scope, gut symbionts of the wood-feeding termites Coptotermes formosanus and Reticulitermes chinenesis were used for the screening of manganese peroxidase (MnP) producing yeasts intended for decolorization and detoxification of textile azo dyes, such as Acid Orange 7 (AO7). To this end, nine out of 38 yeast isolates exhibited high levels of extracellular MnP activity ranging from 23 to 27 U/mL. The isolate PPY-27, which had the highest MnP activity, was able to decolorize various azo dyes with an efficiency ranging from 87.2 to 98.8%. This isolate, which represents the molecularly identified species Meyerozyma caribbica, was successfully characterized in terms of morphological and physiological traits, as well as enzymatic activities. Almost complete decolorization was achieved by the MnP-producing M. caribbica strain SSA1654 after 6 h of incubation with 50 mg/L of the sulfonated azo dye AO7 at 28 °C with an agitation speed of 150 rpm. The maximum decolorization efficiency of AO7 reached 93.8% at 400 mg/L. The decolorization of AO7 was confirmed by Fourier transform infrared (FTIR) and UV–Vis spectral analysis. High performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC–MS) were used to identify AO7 decomposition intermediates. Based on UV–Vis spectra, FTIR, HPLC, and GC–MS analyses, a plausible AO7 biodegradation mechanism pathway was explored, showing azo bond (-N=N-) cleavage and toxic aromatic amines mineralization CO2 and H2O. Microtox® and phytotoxicity assays confirmed that the AO7 metabolites produced by the strain SSA1654 were almost non-toxic compared to the original sulfonated azo dye.

Comparative Anaerobic Decolorization of Azo Dyes by Carbon-Based Membrane Bioreactor

This study used a novel integrated technology of ceramic supported carbon membrane (CSCM) to degrade azo dyes through an anaerobic mixed culture. The CSCM worked simultaneously as biofilm support, redox mediator, and nano-filter to enhance the dye decolorization efficiency. The decolorization of Acid Orange 7 (AO7) was initially investigated with and without microorganisms in both ceramic support (CS) and CSCM reactors. The CSCM bioreactor (B-CSCM), operated with microorganisms, gave a maximum decolorization of 98% using a CSCM evolved from 10% weight (wt.) of Matrimid 5218 solution. To know the influence of permeate flow, feed concentration, and dye structure on the decolorization process, different B-CSCMs for dye removal experiments were studied over monoazo AO7, diazo Reactive Black 5 (RB5), and triazo Direct Blue 71 (DB71). The highest color removal, operated with 50 mg·L−1 feed solution and 0.05 L·m−2·h−1 of permeate flux, was 98%, 82%, and 72%, respectively, for AO7, RB5, and DB71. By increasing these parameters to 100 mg·L−1 and 0.1 L·m−2·h−1, the decolorization rate of dye solution still achieved 37% for AO7, 30% for RB5, and 26% for DB71. In addition, the system was run for weeks without apparent loss of activity. These findings make evident that the combined phenomena taking place in CSCM bioreactor result in an efficient, cost-effective, and ecofriendly azo dye decolorization method.

Electro-enhanced heterogeneous activation of peroxymonosulfate via acceleration of Fe(III)/Fe(II) redox cycle on Fe-B catalyst

Heterogeneous catalytic oxidation based on iron species for peroxymonosulfate (PMS) activation is considered as one of the most attractive strategies for wastewater treatment. However, the rate-limiting regeneration of Fe(II) from Fe(III) heavily hampers the efficient activation of PMS. In this study, the introduction of electric field to the Fe-supported bentonite (Fe-B) activated PMS process was proposed to enhance the Fe(III)/Fe(II) redox cycle. The Fe-B catalyst performed well in the removal of Acid Orange 7 (AO7) through the synergistic effect of electrolysis and the continuous redox cycle of Fe(III)/Fe(II) for PMS activation. The use of 0.5 g L−1 Fe-B catalyst and 10 mM PMS yielded nearly complete removal of the AO7 (50 mg L−1) in 60 min at 2 mA cm−2 of current density. Based on the results of electron paramagnetic resonance (EPR) spectroscopy, chemical quenching tests, X-ray photoelectron spectroscopy (XPS) analysis, and electrochemical measurements, the decolorization of AO7 was dominantly attributed to surface-bound radicals (SO4•−ads and •OHads) and also the direct electron transfer at DSA anode. Moreover, the electro/Fe-B/PMS system showed an effective pH range from 2.6 to 9.0 and the abatement of AO7 was slightly affected in the presence of natural background anions. This work provides a feasible strategy of PMS activation by cost-effective Fe-B catalyst coupling with electric field and gives an insight into the accelerated oxidation of recalcitrant pollutants.

Experimental investigation on dye wastewater treatment with reverse electrodialysis reactor powered by salinity gradient energy

A novel advanced oxidation process technology for organic wastewater treatment was proposed in this paper. The working principle is that a low-grade heat (LGH) is first converted into a salinity gradient energy (SGE), and then the SGE is converted into the degradation energy of organic pollutions by a reverse electrodialysis (RED) reactor. To verify the feasibility of converting a SGE into a degradation energy by a RED reactor, an experimental investigation of dye wastewater treatment with a RED reactor powered by SGE had been done. The results showed that the output current of RED reactor, operating parameters of electrode rinse solution (ERS) and degradation circulation modes have effects on the decolorization of acid orange 7 (AO7) dye wastewater. Under the present experimental conditions, after 20 min treatment, the decolorization efficiencies of AO7 dye wastewater for the independent degradation circulation mode reached 99.93% and 96.52% in the anodic and cathodic loops respectively, while that for the synergetic degradation circulation mode reached 82.85%.

The removal of azo dye from aqueous solution by oxidation with peroxydisulfate in the presence of granular activated carbon: Performance, mechanism and reusability

Granular activated carbon (GAC) was used as catalyst for the activation of peroxydisulfate (PDS) to decolorize and degrade Acid Orange 7 (AO7) in water. EPR spectra and radical quencher experiments were employed to identify the active species for AO7 oxidation in the PDS/GAC system. Linear sweep voltammetry (LSV) and chronoamperometry test were carried out to identify the contribution of nonradical mechanism for AO7 decay. The investigation of crucial operational parameters on the decolorization indicated 100 mg/L AO7 can be almost totally decolorized in a broad range of pH. Common inorganic anions adversely affect the AO7 decolorization process and the inhibition was in the order of: HCO3− > H2PO4− > SO42− > Cl− > NO3−. UV–vis spectra showed the destruction of the aromatic moiety of AO7 molecule during the oxidation reaction of the PDS/GAC system. The transformation of nitrogen related to the azo bond in AO7 molecule in this system was observed by monitoring the released N-containing inorganic ions. Recycle experiments showed GAC cannot be reused directly but its catalytic ability can be restored by using electrochemical method.

Biochar-activated persulfate for organic contaminants removal: Efficiency, mechanisms and influencing factors.

Turning biomass into biochar as a multifunctional carbon-based material for water remediation has attracted much research attention. Sawdust and rice husk were selected as feedstock for biochar (BC) production, aiming to explore their performance as a catalyst to activate persulfate (PS) for degrading acid orange 7 (AO7). There was an excellent synergistic effect in the combined BC/PS system. Sawdust biochar (MX) showed a faster and more efficient performance for the AO7 degradation due to its abundant oxygen functional groups, compared to rice husk biochar (DK). In the BC/PS system, AO7 was well decolorized and mineralized. Based on the two-dimensional correlation analysis method, the azo conjugation structure and naphthalene ring of AO7 molecule changed first then benzene ring changed during the reaction. Moreover, AO7 decolorization efficiency increased with the increase of PS concentration and biochar dosage, and the deacrease of pH. Biochar deactivated after used twice. When the biochar reached its adsorption equilibrium of AO7, the AO7 could not be degraded in the BC/PS system. SO4- and OH participated in the reaction together and OH played the main role in activating PS to AO7 decolorization based on the radical scavengers experiment. All of results indicate using biochar to activate PS for degradation of AO7 contaminated water is a promising method.

Degradation of AO7 with Magnetic Fe3O4-CuO Heterogeneous Catalyzed Sodium Percarbonate System

Magnetically recyclable Fe3O4-CuO was synthesized by a one-step hydrothermal method and characterized by scanning electron microscopy coupled with energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD). The degradation of azo dye acid orange 7 (AO7) by percarbonate (SPC) activated with Fe3O4-CuO was studied. The effects of Fe3O4-CuO catalyst loading, SPC concentration, pH value, and common chloride ions on AO7 degradation in the Fe3O4-CuO/SPC system were evaluated. The main reaction mechanism of AO7 degradation was analyzed. The results show that Fe3O4-CuO could effectively activate SPC to degrade AO7 and the reaction was accelerated with the increase of Fe3O4-CuO dosage. The increase of SPC dosage was favorable for the degradation of AO7, but excessive SPC dosage inhibited the degradation of AO7. Common ions (e.g., Cl-) in dye wastewater could promote the degradation of AO7, and the degradation rate increased with increasing concentration of Cl-. The reaction mainly occurred on the surface of the catalyst, and·OH was identified as the main active species for the degradation of AO7. The catalyst Fe3O4-CuO showed excellent stability owing to the high catalytic activity remaining after 4 cycles of repeated use. The Fe3O4-CuO/SPC system achieved a high mineralization rate in the process of decolorization of AO7.

Synthesis and characterization of ZnO@RSDBC composites and their Photo-Oxidative degradation of Acid Orange 7 in water

In this study, a novel series of rectorite/sludge derived biochar (RSDBC) supporting ZnO (ZnO@RSDBC) composites were fabricated and characterized by scanning electron microscope, transmission electron microscope, fourier transform infrared spectroscopy, nitrogen gas uptake, UV–Vis absorption spectroscopy and X-ray diffraction techniques. From the SEM and TEM results, ZnO particles were well loaded on RSDBC, forming a core-shell ZnO@RSDBC structure. The observed strong XRD and FTIR characteristic peaks indicated that the ZnO@RSDBC was successfully synthesized. The calculated band gap energy was 3.25 eV which the result was in agreement with the theoretical band gap value of ZnO. After characterization, the photocatalytic performances of ZnO@RSDBC catalyst were evaluated by the heterogeneous Photo-Oxidative process (ZnO@RSDBC/PS/Vis) for the elimination of Acid Orange 7 (AO7). Key factors affecting the reaction were tested, including initial pH, PS concentration, catalyst dosage, initial dye concentration, and reaction temperature. The optimal conditions were found to be: PS concentration 2 mM; catalyst dosage 0.9 g/L; initial pH value 7.0 and 30 °C of reaction temperature. Further radical quenching tests of different scavengers showed that h+、SO4•− and HO• are responsible in the process of AO7 decolorization. In addition, the sample exhibited high color removal ability (95%) and stable performance after three successive runs. The catalyst also presented excellent removal effect for Methyl orange, Rhodamine B and Methylene blue. These results indicate that ZnO@RSDBC is an efficient Photo-Oxidative catalyst for remediation of dyes.

Inducing laccase activity in white rot fungi using copper ions and improving the efficiency of azo dye treatment with electricity generation using microbial fuel cells.

This work presents a white rot fungus-microbial fuel cell (WRF-MFC) that uses WRF that is grown at its cathode. Adding Cu2+ to the fungi-containing solid medium stimulated WRF-secreting laccase, which catalyzed the redox reaction in the MFC and thereby promoting the generation of electricity. Adding 12.5 mg L-1 Cu2+ to a G.lucidum-containing medium provided the greatest laccase stimulation and increased the laccase activity by a factor of 1.6. Adding 12.5 mg L-1 Cu2+ to the WRF chamber of WRF-MFC increased its decolorization of Acid Orange 7 (AO-7) and increased its power density to 223 mW m-2, which was 1.77 times that of an MFC without WRF. The enhancement of decolorization and electricity generation improved the performance of the WRF-MFC, indicating that a laccase-catalyzed cathode has great potential effectiveness in microbial fuel cells.

Decolorization of Acid Orange 7 by extreme-thermophilic mixed culture

Although a large amount of textile wastewater is discharged at high temperatures, azo dye reduction under extreme-thermophilic conditions by mixed cultures has gained little attention. In this study, Acid Orange 7 (AO7) was used as the model azo dye to demonstrate the decolorization ability of an extreme-thermophilic mixed culture. The results showed that a decolorization efficiency of over 90% was achieved for AO7. The neutral red (NR, 0.1 mM) could promote AO7 decolorization, in which the group of Cell + NR offered the highest decolorization rate of 1.568 1/h and t1/2 was only 0.44 h, whereas after CuCl2 addition, the decolorization rate (0.141 1/h) was lower and t1/2 (4.92 h) was much longer. Thus, CuCl2 notably inhibited this process. Caldanaerobacter (64.0%) and Pseudomonas (25.4%) were the main enriched bacteria, which were not reported to have the ability for dye decolorization. Therefore, this study extends the application of extreme-thermophilic biotechnology.

Optimization and mechanism of Acid Orange 7 removal by powdered activated carbon coupled with persulfate by response surface method.

In this study, powder activated carbon (PAC) utilized to activate peroxydisulfate (PDS) was investigated for decolorization of Acid Orange 7 (AO7). The results indicated a remarkable synergistic effect in the PAC/PDS system. The effect of PAC, PDS dosages and initial pH on AO7 decolorization were studied and the processes followed first-order kinetics. Response surface method with central composite design (CCD) model was utilized to optimize these three factors and analyze the combined interaction. The optimum condition for the decolorization rate of AO7 was analyzed as the following: PAC (0.19 g/L), PDS (1.64 g/L), and initial pH (4.14). Cl- and SO4 2- showed a promoting effect on AO7 decolorization while HCO3 - had a slightly inhibiting effect. Quenching experiments confirmed that both sulfate and hydroxyl radicals were the oxidizing species, and the oxidation reaction occurred on the surface of PAC. The results of UV-vis spectrum with 100% decolorization rate and the 50% total organic carbon reduction indicated highly efficient decolorization and mineralization of AO7 in the PAC/PDS system. Finally, the recovery performance of PAC was studied and the result indicated PAC had poor reuse in reactivity.

Improvement of dyes degradation using hydrofluoric acid modified biochar as persulfate activator

ABSTRACTThe hydrofluoric acid modified biochar (HF-BC) was obtained, aiming to improve its performance for activating persulfate (PS) to make acid orange 7 (AO7) degraded in water solution. Results showed that the surface area, micropore volume, carboxyl and phenolic hydroxyl group content of HF-BC increased by 171%, 172%, 23.8% and 50%, respectively, compared to unmodified biochar (BC). The decolorization of AO7 in HF-BC/PS and BC/PS systemwas much more rapid and efficient than that in HF-BC, BC and PS alone system. For the HF-BC/PS system, the AO7 was removal of 99.8%, much higher than that of BC/PS system, probably because of its better surface characteristics. Moreover, for the HF-BC/PS system, it was the higher PS concentration and HF-BC dosage that caused greater AO7 degradation rates, and lower pH was favorable for the degradation. Our results provided a novel method to design biochar as an activator for persulfate-based remediation of dye wastewater.Abbreviations: HF-BC, hydrofluoric acid modified biochar; BC, unmodified biochar; AO7, Acid orange 7; PS, persulfate