Photoactive material and recognition element are two crucial factors which determine the sensitivity and selectivity of the photoelectrochemical (PEC) sensor. Herein we developed a novel PEC aptamer ...sensor for the specific detection of kanamycin using water-dispersible graphite-like carbon nitride (w-g-C3N4) as visible light-active material and aptamer as the biorecognition element. While a suitable amount of graphene oxide (GO) was doped in w-g-C3N4, the visible light photocurrent response was enhanced, which was beneficial to the construction of PEC sensor. On the other hand, the large specific surface area and π-conjugated structure of GO/w-g-C3N4 provided an excellent platform for immobilizing the kanamycin-binding DNA aptamer on the surface of the sensor via π–π stacking interaction. On such a sensor, the capture of kanamycin molecules by aptamer resulted in increased photocurrent. The PEC response of the sensor was found to be linearly proportional to the concentration of kanamycin in the range from 1 nM to 230 nM with a detection limit (3S/N) of 0.2 nM. Moreover, the proposed sensor displayed high selectivity, good reproducibility, and high stability, demonstrating the successful combination of GO/w-g-C3N4 with aptamer in fabricating high performance PEC sensors.
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•Mesoporous-microporous structure created by activation promoted electron transfer.•Activation process decreased N− and O−containing functional groups on the biomass.•Activated ...chestnut shell anode showed higher power output compared to carbon cloth.•The chestnut shell anode had lower internal resistance compared to other biomass.
Microbial fuel cells (MFCs) are promising biotechnologies tool to harvest electricity by decomposing organic matter in waste water, and the anode material is a critical factor in determining the performance of MFCs. In this study, chestnut shell is proposed as a novel anode material with mesoporous and microporous structure prepared via a simple carbonization procedure followed by an activation process. The chemical activation process successfully modified the macroporous structure, created more mesoporous and microporous structure and decreased the O−content and pyridinic/pyrrolic N groups on the biomass anode, which were beneficial for improving charge transfer efficiency between the anode surface and microbial biofilm. The MFC with activated biomass anode achieved a maximum power density (23.6 W m−3) 2.3 times higher than carbon cloth anode (10.4 W m−3). This study introduces a promising and feasible strategy for the fabrication of high performance anodes for MFCs derived from cost-effective, sustainable natural materials.
Red mud was evaluated as an alternative skeleton builder combined with Fenton's reagent in sewage sludge conditioning. The results show that red mud combined with Fenton's reagent showed good ...conditioning capability with the pH of the filtrate close to neutrality, indicating that red mud acted as a neutralizer as well as a skeleton builder when jointly used with Fenton's reagent. Through response surface methodology (RSM), the optimal dosages of Fe2+, H2O2 and red mud were proposed as 31.9, 33.7 and 275.1 mg/g DS (dry solids), respectively. The mechanism of the composite conditioner could be illuminated as follows: (1) extracellular polymeric substances (EPS), including loosely bound EPS and tightly bound EPS, were degraded into dissolved organics, e.g., proteins and polysaccharides; (2) bound water was released and converted into free water due to the degradation of EPS; and (3) morphology of the conditioned sludge exhibited a porous structure in contrast with the compact structure of raw sludge, and the addition of red mud formed new mineral phases and a rigid lattice structure in sludge, allowing the outflow of free water. Thus, sludge dewatering performance was effectively improved. The economic assessment for a wastewater treatment plant of 370,000 equivalent inhabitants confirms that using red mud conditioning, combined with Fenton's reagent, leads to a saving of approximately 411,000 USD/y or 50.8 USD/t DS comparing with using lime and ordinary Portland cement combined with Fenton's reagent, and approximately 612,000 USD/y or 75.5 USD/t DS comparing with the traditional treatment.
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•The feasibility of using red mud as a novel skeleton builder was demonstrated.•The degradations of LB-EPS and TB-EPS into dissolved organics were determined.•The conversion of bound water into free water was illustrated by DSC.•New mineral phases and a rigid porous structure were identified by XRD and SEM.•The economic benefits were confirmed for a WWTP of 370,000 IE.
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•Fe2+/S2O82−−phosphogypsum for sludge conditioning is firstly proposed.•SO4− was identified as the dominant radical by radical quenching experiment.•CaSO4·2H2O could be newly ...generated and acted as an effective skeleton builder.•The transforms of proteins and polysaccharides in floc were determined.•The bound water was released and reduced significantly.
High water affinity of extracellular polymeric substances (EPS) and high compressibility of sewage sludge solids have negative impacts on sludge dewatering. In this study, a composite conditioner, Fe2+–activated sodium persulfate (denoted as Fe2+/SPS) combined with thermal–pretreated phosphogypsum (PG), was used to improve the sludge dewaterability. The mechanism of the composite conditioning of sewage sludge was elucidated: the proteins in tightly bound EPS were transferred into the filtrate and loosely bound EPS, and the polysaccharides in loosely and tightly bound EPS were transferred into the filtrate; the bound water was released and reduced from 2.60g/gDS (dry solid) initially to 0.81g/gDS; specific resistance to filtration and capillary suction time were reduced by 91.6% and 88.4%, respectively. Radical quenching experiment indicated that sulfate radical (SO4−) is the dominant free radical and plays an important role in determining the oxidation–reduction potential during conditioning. Moreover, both the XRD and SEM results clearly showed that Fe2+/SPS combined with PG promoted the generation of column–shaped dihydrate gypsum in the conditioned sludge. Thus, the dihydrate gypsum crystals could act as skeleton builders, which create a more permeable and rigid lattice structure of the sludge cake. The improvement of sludge dewatering was confirmed by diaphragm filter press dewatering process, which yielded 45.7wt% cake moisture content and 91.7% dewatering efficiency.
TiO(2) film deposited on glassy carbon electrode surface was prepared via the liquid phase deposition (LPD). The deposited TiO(2) film before and after calcination was characterized with scanning ...electron microscopy (SEM) and X-ray diffraction (XRD). Based on the high photoelectrochemical activity of calcined LPD TiO(2) film, the photoelectrocatalytic degradation of benzotriazole (BTA) was investigated. Compared with the electrochemical oxidation process, direct photolysis or photocatalysis for treatment of BTA, a synergetic photoelectrocatalytic degradation effect was observed using the LPD TiO(2) film-coated electrode. Various factors influencing the photoelectrocatalytic degradation of BTA such as film calcination, applied bias potential, pH value, supporting electrolyte concentration and initial concentration of BTA were investigated. The COD removal for BTA solution was analyzed to evaluate the mineralization of the PEC process. Based on the degradation experimental results, a possible photoelectrocatalytic degradation mechanism for BTA was proposed.
Poly-zinc silicate (PZSS) is a new type of coagulant with cationic polymer synthesized by polysilicic acid and zinc sulfate. It has been used in several sorts of wastewaters treatment, but not used ...in oily wastewater treatment. In this study, we investigated the coagulation/flocculation of oil and suspended solids in heavy oil wastewater (HOW) by PZSS and anion polyacrylamide (A-PAM). The properties of PZSS cooperated with A-PAM were compared with PAC and PFS in dosages, PAMs amount, settling time, pH value and flocs morphology. The results showed that PZSS was more efficient than PAC and PFS. Under the optimum experimental conditions of coagulation/flocculation (dosage: 100
mg/L, A-PAM dosage: 1.0
mg/L, settling time time: 40
min and pH 6.5–9.5), more than 99% of oil was removed and suspended solid value less than 5
mg/L by using PZSS cooperated with A-PAM, which could satisfy the demands of the pre-treatment process for HOW to be reused in the steam boiler or recycled into the injecting well.
► A novel joint usage of Fenton’s reagent and skeleton builders was investigated. ► Fenton’s reagent and skeleton builders are referred as F–S composite conditioner. ► The research focuses on F–S ...conditioner’s efficacies and operational parameters. ► The F–S conditioner can reduce SRF of sludge effectively at a lower dosage.
Physical conditioners, often known as skeleton builders, are commonly used to improve the dewaterability of sewage sludge. This study evaluated a novel joint usage of Fenton’s reagent and skeleton builders, referred to as the F–S inorganic composite conditioner, focusing on their efficacies and the optimization of the major operational parameters. The results demonstrate that the F–S composite conditioner for conditioning sewage sludge is a viable alternative to conventional organic polymers, especially when ordinary Portland cement (OPC) and lime are used as the skeleton builders. Experimental investigations confirmed that Fenton reaction required sufficient time (80min in this study) to degrade organics in the sludge. The optimal condition of this process was at pH=5, Fe2+=40mgg−1 (dry solids), H2O2=32mgg−1, OPC=300mgg−1 and lime=400mgg−1, in which the specific resistance to filtration reduction efficiency of 95% was achieved.
We prepared platelike Mo-doped WO3 films (Mo–WO3) deposited with Sb2S3 for photoelectrocatalytic (PEC) water splitting under visible-light illumination at extremely low input energy (1 mW cm–2). The ...5% Mo–WO3 film exhibited optimal PEC water-splitting performance. Furthermore, Sb2S3/5% Mo–WO3 composite film achieved the highest photocurrent density of 0.42 mA cm–2, nearly 20 times as high as that of 5% Mo–WO3 film. The outstanding PEC water-splitting performance was mainly attributed to synergistic effects of Mo doping and deposited Sb2S3; that is, the enhanced PEC performance not only was assigned to the broadened optical spectrum but also improved electron–hole pairs separation and transfer efficiency. Density functional theory calculation revealed that Mo dopant can modulate the intrinsic electronic structure of WO3 and introduce impurity energy levels resulting from the hybridization between M 3d and O 2p states around the Fermi level, resulting in improved electrical conductivity. Therefore, this work offers new insight for designing metal elements doping into WO3 associated with multifunctional electrode materials for high PEC visible-light-induced water-splitting activity in neutral electrolyte.
► The modified model is suitable for simulating the biological conversion processes. ► Modified model includes simultaneous storage-growth, nitrification–denitrification. ► We have adjusted 11 ...important parameters of model according to our analysis.
The activated sludge model No. 3 (ASM3) was modified to describe the biological reactions in aerobic granular sludge SBR. The simultaneous storage and growth, nitrification and denitrification were all accounted for in modified model. The sensitivities of effluent COD, NH4+–N, and TN toward the stoichiometric and kinetic coefficients were analyzed. A standard set of parameters obtained from a combination of literature data was chosen for the model. The experimental results for the time profile of COD, NH4+–N, and TN in a typical cycle were used to verify the ASM3 model. The verification results show the model established is applicable for simulating the performance of an aerobic granule-based SBR. A comparison of the measured and predicted values of substrate removal for both the modified ASM3 and the original ASM3 was also performed. The verification and comparison results show the modified ASM3 model describes the aerobic granule-based SBR better and more mechanistically.
ZnFe2O4 nanoparticles （ZFNPs） were developed as catalyst for the degradation of benzotriazole （BTA） by heterogeneous photoelectro- Fenton （PE-Fenton） like process. ZFNPs were prepared by a ...co-precipitation process and then characterized with transmission electron microscopy （TEM）, X-ray fluorescence （XRF）, X-ray diffraction （XRD） and BET surface area. Using such ZFNPs as catalyst, the degradation of BTA was investigated. Due to the high catalytic activity of ZFNPs, PE-Fenton like process showed efficient degradation of BTA. The influencing factors such as pH, dosage of ZFNPs, applied potential and initial concentration of BTA were systematically investigated. Under the optimum conditions, 91.2% of BTA was removed after 180 rain treatment.
