AnSBBR Applied to Organic Matter and Sulfate Removal: Interaction Effect Between Feed Strategy and Cod/Sulfate Ratio

A mechanically stirred anaerobic sequencing batch reactor containing anaerobic biomass immobilized on polyurethane foam cubes, treating low-strength synthetic wastewater (500 mg COD L^?1), was operated under different operational conditions to assess the removal of organic matter and sulfate. These conditions were related to fill time, defined by the following feed strategies: batch mode of 10 min, fed-batch mode of 3 h and fed-batch mode of 6 h, and COD/[SO₄ ^2?] ratios of 1.34, 0.67, and 0.34 defined by organic matter concentration of 500 mg COD L^?1 and sulfate concentrations of 373, 746, and 1,493 mg SO₄ ^2? L^?1 in the influent. Thus, nine assays were performed to investigate the influence of each of these parameters, as well as the interaction effect, on the performance of the system. The reactor operated with agitation of 400 rpm, total volume of 4.0 L, and treated 2.0 L synthetic wastewater in 8-h cycles at 30?±?1°C. During all assays, the reactor showed operational stability in relation to the monitored variables such as COD, sulfate, sulfide, sulfite, volatile acids, bicarbonate alkalinity, and solids, thus demonstrating the potential to apply this technology to the combined removal of organic matter and sulfate. In general, the results showed that the 3-h fed-batch operation with a COD/[SO₄ ^2?] ratio of 0.34 presented the best conditions for organic matter removal (89%). The best efficiency for sulfate removal (71%) was accomplished during the assay with a COD/[SO₄ ^2?] ratio of 1.34 and a fill time of 6 h. It was also observed that as fill time and sulfate concentration in the influent increased, the ratio between removed sulfate load and removed organic load also increased. However, it should be pointed out that the aim of this study was not to optimize the removal of organic matter and sulfate, but rather to analyze the behavior of the reactor during the different feed strategies and applied COD/[SO₄ ^2?] ratios, and mainly to analyze the interaction effect, an aspect that has not yet been explored in the literature for batch reactors.     

Anaerobic Digestion of Sugarcane Vinasse Through a Methanogenic UASB Reactor Followed by a Packed Bed Reactor

The anaerobic treatment of raw vinasse in a combined system consisting in two methanogenic reactors, up-flow anaerobic sludge blanket (UASB) + anaerobic packed bed reactors (APBR), was evaluated. The organic loading rate (OLR) was varied, and the best condition for the combined system was 12.5 kg COD m^?3day^?1 with averages of 0.289 m³ CH₄ kg COD r^?1for the UASB reactor and 4.4 kg COD m^?3day^?1 with 0.207 m³ CH₄ kg COD r^?1 for APBR. The OLR played a major role in the emission of H₂S conducting to relatively stable quality of biogas emitted from the APBR, with H₂S concentrations <10 mg L^?1. The importance of the sulphate to COD ratio was demonstrated as a result of the low biogas quality recorded at the lowest ratio. It was possible to develop a proper anaerobic digestion of raw vinasse through the combined system with COD removal efficiency of 86.7% and higher CH₄ and a lower H₂S content in biogas.     

Optimization of Lactic Acid Production by Pellet-Form Rhizopus oryzae in 3-L Airlift Bioreactor Using Response Surface Methodology

The influence of two key environmental factors, pH and oxygen transfer coefficient (k _La), was evaluated on the lactic acid production as the main answer and, on the size of cell pellets of the fungal strain Rhizopus oryzae KPS106, as second dependant answer by response surface methodology using a central composite design. The results of the analysis of variance and modeling demonstrated that pH and k _La had a significant effect on lactic acid production by this strain. However, no interaction was observed between these two experimental factors. pH and k _La had no significant influence on the pellet size. Optimal pH and k _La of the fermentation medium for lactic acid production from response surface analysis was 5.85 and of 3.6 h^?1, respectively. The predicted and experimental lactic acid maximal values were 75.4 and 72.0 g/l, respectively, with pellets of an average of 2.54?±?0.41 mm. Five repeated batches in series were conducted with a mean lactic acid production of 77.54 g/l. The productivity was increased from 0.75 in the first batch to 0.99 g/l h in the last fifth batch.     

Characterization of a Marine Microbial Community Used for Enhanced Sulfate Reduction and Copper Precipitation in a Two-Step Process

Marine microorganisms that are obtained from hydrothermal vent sediments present a great metabolic potential for applications in environmental biotechnology. However, the work done regarding their applications in engineered systems is still scarce. Hence, in this work, the sulfate reduction process carried out by a marine microbial community in an upflow anaerobic sludge blanket (UASB) reactor was investigated for 190 days under sequential batch mode. The effects of 1000 to 5500 mg L^?1 of SO₄ ^?2 and the chemical oxygen demand (COD)/SO₄ ^?2 ratio were studied along with a kinetic characterization with lactate as the electron donor. Also, the feasibility of using the sulfide produced in the UASB for copper precipitation in a second column was studied under continuous mode. The system presented here is an alternative to sulfidogenesis, particularly when it is necessary to avoid toxicity to sulfide and competition with methanogens. The bioreactor performed better with relatively low concentrations of sulfate (up to 1100 mg L^?1) and COD/SO₄ ^?2 ratios between 1.4 and 3.6. Under the continuous regime, the biogenic sulfide was sufficient to precipitate copper at a removal rate of 234 mg L^?1 day^?1. Finally, the identification of the microorganisms in the sludge was carried out; some genera of microorganisms identified were Desulfitobacterium and Clostridium.     

Biogas Plasticization Coupled Anaerobic Digestion: Continuous Flow Anaerobic Pump Test Results

In this investigation, the Anaerobic Pump (®TAP) and a conventional continuous flow stirred tank reactor (CFSTR) were tested side by side to compare performance. TAP integrates anaerobic digestion (AD) with biogas plasticization–disruption cycle to improve mass conversion to methane. Both prototypes were fed a “real world” 50:50 mixture of waste-activated sludge (WAS) and primary sludge and operated at room temperature (20°C). The quantitative results from three steady states show TAP peaked at 97% conversion of the particulate COD in a system hydraulic residence time (HRT) of only 6 days. It achieved a methane production of 0.32 STP cubic meter CH₄ per kilogram COD fed and specific methane yield of 0.78 m³ CH₄ per cubic meter per day. This was more than three times the CFSTR specific methane yield (0.22 m³ CH₄ per cubic meter per day) and more than double the CFSTR methane production (0.15 m³ CH₄ per kilogram COD fed). A comparative kinetics analysis showed the TAP peak substrate COD removal rate (R _o) was 2.24 kg COD per cubic meter per day, more than three times the CFSTR substrate removal rate of 0.67 kg COD per cubic meter per day. The three important factors contributing to the superior TAP performance were (1) effective solids capture (96%) with (2) mass recycle and (3) stage II plasticization–disruption during active AD. The Anaerobic Pump (®TAP) is a high rate, high efficiency–low temperature microbial energy engine that could be used to improve renewable energy yields from classic AD waste substrates like refuse-derived fuels, treatment plant sludges, food wastes, livestock residues, green wastes and crop residuals.     

Biodiesel Residual Glycerol Metabolism by Klebsiella pneumoniae: Pool of Metabolites Under Anaerobiosis and Oxygen Limitation as a Function of Feeding Rates

The metabolism of residual glycerol from biodiesel synthesis by Klebsiella pneumoniae BLh-1 was investigated in this study. Batch and fed-batch cultivations were performed in bioreactors under anaerobic and oxygen limitation conditions. Results of batch cultivations showed that the main product was 1,3-propanediol (1,3-PD) in both conditions, although the higher yields and productivities (0.46 mol mol^?1 glycerol and 1.22 g?L^?1?h^?1, respectively) were obtained under anaerobic condition. Large amounts of ethanol were also produced under batch anaerobic condition, peaking at 12.30 g?L^?1. Batch cultivations under oxygen limitation were characterized by faster growth kinetics, with higher biomass production but lower conversions of glycerol into 1,3-PD, with yields and productivities of 0.33 mol mol^?1 glycerol and 0.99 g?L^?1?h^?1, respectively. The fed-batch cultivations were carried out in order to investigate the effects of feeding of raw glycerol on cells. Fed-batch under anaerobiosis showed that 1,3-PD and ethanol concentrations increased with the feeding rate, with maximal productions of 26.12 and 19.2 g?L^?1, respectively. The oxygen limitation conditions diverted the bacterium metabolism to an elevated lactic acid formation, reaching 59 g?L^?1 in higher feeding rates of glycerol, but lowering the production of ethanol.     

Phospholipid/Polydiacetylene Vesicle-Based Colorimetric Assay for High-Throughput Screening of Bacteriocins and Halocins

Multi-phase anaerobic reactor for H₂ and CH₄ production from paperboard mill wastewater was studied. The reactor was operated at hydraulic retention times (HRTs) of 12, 18, 24, and 36 h, and organic loading rates (OLRs) of 2.2, 1.5, 1.1, and 0.75 kg chemical oxygen demand (COD)/m³ day, respectively. HRT of 12 h and OLR of 2.2 kg COD/m³ day provided maximum hydrogen yield of 42.76?±?14.5 ml/g COD_removed and volumetric substrate uptake rate (?rS) of 16.51?±?4.43 mg COD/L h. This corresponded to the highest soluble COD/total COD (SCOD/TCOD) ratio of 56.25?±?3.3 % and the maximum volatile fatty acid (VFA) yield (Y_VFA) of 0.21?±?0.03 g VFA/g COD, confirming that H₂ was mainly produced through SCOD conversion. The highest methane yield (18.78?±?3.8 ml/g COD_removed) and ?rS of 21.74?±?1.34 mgCOD/L h were achieved at an HRT of 36 h and OLR of 0.75 kg COD/m³ day. The maximum hydrogen production rate (HPR) and methane production rate (MPR) were achieved at carbon to nitrogen (C/N) ratio of 47.9 and 14.3, respectively. This implies the important effect of C/N ratio on the distinction between the dominant microorganism bioactivities responsible for H₂ and CH₄ production.     

Animal Bone Char Solubilization with Itaconic Acid Produced by Free and Immobilized Aspergillus terreus Grown on Glycerol-Based Medium

Cells of Aspergillus terreus, free and immobilized in polyurethane foam, were employed in itaconic acid fermentation processes on glycerol-based media. The purpose was to assess their suitability for animal bone char solubilization and the development of a biotechnological alternative to P fertilizers chemically produced from rock phosphate. Animal bones constitute a renewable source of P that can replace the traditionally used finite, nonrenewable rock phosphate as a P source. Glycerol was an excellent substrate for growth (10.2 g biomass L^?1) and itaconic acid production (26.9 g?L^?1) by free fungal cells after 120-h fermentation. Simultaneously, A. terreus solubilized the insoluble phosphate to a yield of 23 to 50 %, depending on the particle size and concentration. Polyurethane foam cut into cubes of 0.5–0.6 cm per side, with 0.3 mm pore size and applied at 2.0 g?L^?1 proved to be an excellent cell carrier. In repeated batch fermentation, the immobilized mycelium showed a high capacity to solubilize animal bone char, which resulted on average in 168.8 mg?L^–1 soluble phosphate per 48-h cycle and 59.4 % yield (percent of total phosphate) registered in the fourth batch.     

Pretreatment of Chicken Feather Waste for Improved Biogas Production

This study deals with the utilization of chicken feather waste as a substrate for anaerobic digestion and improving biogas production by degradation of the compact structure of the feather keratin. In order to increase the digestibility of the feather, different pretreatments were investigated, including thermal pretreatment at 120 °C for 10 min, enzymatic hydrolysis with an alkaline endopeptidase [0.53–2.66 mL/g volatile solids (VS) feathers] for 0, 2, or 24 h at 55 °C, as well as a combination of these pretreatments. The effects of the treatments were then evaluated by anaerobic batch digestion assays at 55 °C. The enzymatic pretreatment increased the methane yield to 0.40 Nm³/kg VS_added, which is 122 % improvement compared to the yield of the untreated feathers. The other treatment conditions were less effective, increasing the methane yield by 11–50 %. The long-term effects of anaerobic digestion of feathers were examined by co-digestion of the feather with organic fraction of municipal solid waste performed with and without the addition of enzyme. When enzyme was added together with the feed, CH₄ yield of 0.485 Nm³/kg VS^?1 d^?1 was achieved together with a stable reactor performance, while in the control reactor, a decrease in methane production, together with accumulation of undegraded feather, was observed.     

Chemiluminescent Determination of Vitamin B12 Using Charge Coupled Device (CCD)

A method was developed for the determination of vitamin B₁₂ based on the enhancement of cobalt (II) on the chemiluminescence (CL) reaction between luminol and percarbonate (powerful source of hydrogen peroxide). The release of cobalt (II) from the vitamin B₁₂ was reached by a simple and fast microwave digestion (20 s microwave digestion time and a mix of nitric acid and hydrogen peroxide). A charge coupled device (CCD) photodetector, directly connected to the cell, coupled with a simple continuous flow system was used to obtain the full spectral characteristics of cobalt (II) catalyzed luminol-percarbonate reaction.

The optima experimental conditions were established: 8.0 m mol L^?1 luminol in a 0.075 mol L^?1 carbonate buffer (pH 10.0) and 0.15 mol L^?1 sodium percarbonate, in addition to others experimental parameters as 0.33 mL s^?1 flow rate and 2 s integration time, were the experimental conditions which proportionate the optimum CL emission intensity. The emission data were best fitted with a second-order calibration graph over the cobalt (II) concentration range from 4.00 to 300 µ g L^?1 (r² = 0.9990), with a detection limit of 0.42 µ g L^?1. The proposed method was successfully applied to the determination of vitamin B₁₂ in pharmaceuticals.     

Preconcentration of trace amounts of cobalt (II) ions in water and agricultural products samples using of 5-(4-dimethylaminobenzylidene) rhodanin modified SBA-15 sorbent prior to FAAS determination

In the present study, the ?5-(4-dimethylaminobenzylidene)rhodanin-modified SBA-15? was applied as stable solid sorbent for the separation and preconcentration of trace amounts of cobalt ions in aqueous solution. SBA-15 was modified by ?5-(4-dimethylaminobenzylidene)rhodanin reagent. The sorption of Co²⁺ ions was done onto modified sorbent in the pH range of 6.8–7.9 and desorption occurred in 5.0 mL of 3.0 mol L^?1 HNO₃. The results exhibit a linear dynamic range from 0.01 to 6.0 mg L^?1 for cobalt. Intra-day (repeatability) and inter-day (reproducibility) for 10 replicated determination of 0.06 mg L^?1 of cobalt was ±1.82% and ?±1.97%?. Detection limit was 4.2 µg L^?1 (3S_b, n = 5) and preconcentration factor was 80. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type and interference ions were studied for the preconcentration of Co²⁺. The proposed method was applied for the determination of cobalt in standard samples, water samples and agricultural products.     

Impact of Nitrate Dose on Toluene Degradation under Denitrifying Condition

In this study, we investigated the impact of nitrate dose on toluene degradation by Pseudomonas putida to elucidate the upper limit of nitrate concentration and whether an optimum ratio of nitrate to toluene concentration exists. Batch microcosm studies were conducted in order to monitor toluene degradation for various ratios (2–20) of nitrate to toluene with nitrate concentrations ranging from 0 to 700 mg?L^?1 for a given toluene concentration of 50 and 25 mg?L^?1 during 4-day (short term) and 14-day (long term) incubation time, respectively. The short-term study revealed that nitrate concentration of 500 mg?L^?1 was toxic to bacteria and the optimum concentration was 300 mg?L^?1 yielding the highest toluene degradation rate (0.083 mg?L^?1?h^?1). In the batch study of long term, toluene degradation was limited to 6 days after which the nitrate at 50 mg?L^?1 was depleted, indicating that nitrate was a necessary electron acceptor. For both batch studies, an optimum ratio of 6 was found yielding the highest toluene degradation rate. This indicates that an appropriate nitrate dose is essential for efficient degradation of toluene when bioremediation of groundwater contaminated with toluene is under consideration.     

Effect of Organic Loading Rate and Fill Time on the Biohydrogen Production in a Mechanically Stirred AnSBBR Treating Synthetic Sucrose-Based Wastewater

This study investigated the feasibility to produce biohydrogen of a mechanically stirred anaerobic sequencing batch biofilm reactor (AnSBBR) treating sucrose-based synthetic wastewater. The bioreactor performance (30 °C) was evaluated as to the combined effect of fill time (2, 1.5, and 1 h), cycle length (4, 3, and 2 h), influent concentration (3,500 and 5,250 mg chemical oxygen demand (COD)?L^?1) and applied volumetric organic load (AVOL_CT from 9.0 to 27.0 g COD L^?1 d^?1). AVOLs were varied according to influent concentration and cycle length (t _C). The results showed that increasing AVOL_CT resulted in a decrease in sucrose removal from 99 to 86 % and in improvement of molar yield per removed load (MYRL_S.n) from 1.02 mol H₂?mol carbohydrate^?1 at AVOL_CT of 9.0 g COD L^?1 d^?1 to maximum value of 1.48 mol H₂?mol carbohydrate^?1, at AVOL_CT of 18.0 g COD L^?1 d^?1, with subsequent decrease. Increasing AVOL_CT improved the daily molar productivity of hydrogen (MPr) from 15.28 to 49.22 mol H₂?m^?3 d^?1. The highest daily specific molar productivity of hydrogen (SMPr) obtained was 8.71 mol H₂?kg TVS^?1 d^?1 at an AVOL_CT of 18.0 g COD L^?1 d^?1. Decreasing t _C from 4 to 3 h decreased sucrose removal, increased MPr, and improved SMPr. Increasing influent concentration decreased sucrose removal only at t _C of 2 h, improved MYRL_S,n and MPr at all t _C, and also improved SMPr at t _C of 4 and 3 h. Feeding strategy had a significant effect on biohydrogen production; increasing fill time improved sucrose removal, MPr, SMPr, and MYRL_S,n for all investigated AVOL_CT. At all operational conditions, the main intermediate metabolic was acetic acid followed by ethanol, butyric, and propionic acids. Increasing fill time resulted in a decrease in ethanol concentration.     

Adsorption of Cu(II) and Zn(II) ions from aqueous solutions onto fine powder of Typha latifolia L. root: kinetics and isotherm studies

Fine powder of Typha latifolia L. root was used for adsorption of copper and zinc ions from buffered and nonbuffered aqueous solutions. The adsorption reached equilibrium in 60 min. During this time, more than 90 % of the adsorption process was completed. The effect of initial pH, initial concentration of metal ion, and contact time was investigated in a batch system at room temperature. The optimum adsorption performance was observed at pH 5.00 and 4.25 for nonbuffered solutions of Cu(II) and Zn(II), respectively, while for buffered solutions it occurred at pH 6.00. The total metal uptake decreased on application of ammonium acetate buffer, from 37.35 to 17.00 mg g^?1 and 28.80 to 9.90 mg g^?1 for Cu(II) and Zn(II) solutions, respectively, with 100 mg L^?1 initial concentration. The pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models were used to describe the adsorption kinetics. The experimental data followed the pseudo-second-order kinetic model. The biosorption equilibrium was well described by Langmuir and Freundlich isotherm models.     

Biomethane Production in an AnSBBR Treating Wastewater from Biohydrogen Process

An anaerobic sequencing batch reactor containing immobilized biomass (AnSBBR) was used to produce biomethane by treating the effluent from another AnSBBR used to produce biohydrogen from glucose- (AR-EPHG) and sucrose-based (AR-EPHS) wastewater. In addition, biomethane was also produced from sucrose-based synthetic wastewater (AR-S) in a single AnSBBR to compare the performance of biomethane production in two steps (acidogenic and methanogenic) in relation to a one-step operation. The system was operated at 30 °C and at a fixed stirring rate of 300 rpm. For AR-EPHS treatment, concentrations were 1,000, 2,000, 3,000, and 4,000 mg chemical oxygen demand?(COD)?L^?1 and cycle lengths were 6 and 8 h. The applied volumetric organic loads were 2.15, 4.74, 5.44, and 8.22 g COD L^?1 day^?1. For AR-EPHG treatment, concentration of 4,000 mg COD L^?1 and 4-h cycle length (7.21 g COD L^?1 day^?1) were used. For AR-S treatment, concentration was 4,000 mg COD L^?1 day^?1 and cycle lengths were 8 (7.04 g COD L^?1 day^?1) and 12 h (4.76 g COD L^?1 day^?1). The condition of 8.22 g COD L^?1 day^?1 (AR-EPHS) showed the best performance with respect to the following parameters: applied volumetric organic load of 7.56 g COD L^?1 day^?1, yield between produced methane and removed organic material of 0.016 mol CH₄?g COD^?1, CH₄ content in the produced biogas of 85 %, and molar methane productivity of 127.9 mol CH₄?m^?3 day^?1. In addition, a kinetic study of the process confirmed the trend that, depending on the biodegradability characteristics of the wastewaters used, the two-step treatment (acidogenic for biohydrogen production and methanogenic for biomethane production) has potential advantages over the single-step process.     

Removal of Th4+ ions from aqueous solutions by graphene oxide

The removal of Th⁴⁺ ions from aqueous solutions was investigated using single-layer graphene oxide (GO) as a sorbent which was prepared by the modified Hummers’ method through batch adsorption experiments at room temperature. Structural characterizations of the sorbent were also investigated. The influences of the pH value of solution, contact time, sorbent dose, ionic strength, the initial metal ion concentration and temperature on the adsorption of Th⁴⁺ were also investigated. These results indicated that the adsorption of Th⁴⁺ was dependent on the pH and independent on the ionic strength. The sorbent provided significant Th⁴⁺ removal (>98.7 %) at pH 3.0 and the adsorption equilibrium was achieved after only 10 min. The Langmuir adsorption isotherm fit the absorption profile very closely, and indicated that a maximum adsorption capacity of 1.77 mmol g^?1 of GO (411 mg g^?1) after 2 h. The thermodynamic parameters showed that this adsorption process was endothermic and spontaneous. Moreover, the desorption level of Th⁴⁺ from GO, by using 0.1 mol L^?1 H₂SO₄ as a stripping agent, was 84.2 ± 1.2 %, and that of 0.5 mol L^?1 HNO₃ as a stripping agent, was 79.8 ± 3.0 %.     

Effects of Organic Loading, Influent Concentration, and Feed Time on Biohydrogen Production in a Mechanically Stirred AnSBBR Treating Sucrose-Based Wastewater

An anaerobic sequencing batch biofilm reactor (AnSBBR—total volume 7.5 L; liquid volume 3.6 L; treated volume per cycle 1.5 L) treated sucrose-based wastewater to produce biohydrogen (at 30 °C). Different applied volumetric organic loads (AVOL of 9.0, 12.0, 13.5, 18.0, and 27.0 kg COD m^?3 day^?1), which were varied according to the influent concentration (3,600 and 5,400 mg COD L^?1) and cycle length (4, 3, and 2 h), have been used to assess the following parameters: productivity and yield of biohydrogen per applied and removed load, reactor stability, and efficiency. The removed organic matter (COD) remained stable and close to 18 % and carbohydrates (sucrose) uptake rate remained between 83 and 97 % during operation. The decrease in removal performance of the reactor with increasing AVOL, by increasing the influent concentration (at constant cycle length) and decreasing the cycle lengths (at constant influent concentrations), resulted in lower conversion efficiencies. Under all conditions, when organic load increased there was a predominance of acetic, propionic, and butyric acid as well as ethanol. The highest concentration of biohydrogen in the biogas (24–25 %) was achieved at conditions with AVOL of 12.0 and 13.5 kg COD m^?3 day^?1, the highest daily production rate (0.139 mol H₂?day^?1) was achieved at AVOL of 18.0 kg COD m^?3 day^?1, and the highest production yields per removed and applied load were 2.83 and 3.04 mol H₂?kg SUC^?1, respectively, at AVOL of 13.5 kg COD m^?3 day^?1. The results indicated that the best productivity tends to occur at higher organic loads, as this parameter involves the “biochemical generation” of biogas, and the best yield tends to occur at lower and/or intermediate organic loads, as this parameter involves “biochemical consumption” of the substrate.     

Growth of Chlorella vulgaris on Sugarcane Vinasse: The Effect of Anaerobic Digestion Pretreatment

Microalgae farming has been identified as the most eco-sustainable solution for producing biodiesel. However, the operation of full-scale plants is still limited by costs and the utilization of industrial and/or domestic wastes can significantly improve economic profits. Several waste effluents are valuable sources of nutrients for the cultivation of microalgae. Ethanol production from sugarcane, for instance, generates significant amounts of organically rich effluent, the vinasse. After anaerobic digestion treatment, nutrient remaining in such an effluent can be used to grow microalgae. This research aimed to testing the potential of the anaerobic treated vinasse as an alternative source of nutrients for culturing microalgae with the goal of supplying the biodiesel industrial chain with algal biomass and oil. The anaerobic process treating vinasse reached a steady state at about 17 batch cycles of 24 h producing about 0.116 m³CH₄ kgCOD_vinasse ^?1. The highest productivity of Chlorella vulgaris biomass (70 mg l^?1 day^?1) was observed when using medium prepared with the anaerobic digester effluent. Lipid productivity varied from 0.5 to 17 mg l^?1 day^?1. Thus, the results show that it is possible to integrate the culturing of microalgae with the sugarcane industry by means of anaerobic digestion of the vinasse. There is also the advantageous possibility of using by-products of the anaerobic digestion such as methane and CO₂ for sustaining the system with energy and carbon source, respectively.     

pH-controlled morphological structure and electrochemical performances of polyaniline/nickel hexacyanoferrate nanogranules during electrochemical deposition

To explore the dependences of morphology and electrochemical performance of polyaniline/nickel hexacyanoferrate (PANI/NiHCF) nanogranules on pH value of the reaction system, electrodeposition of PANI/NiHCF nanogranules was performed across a pH range from 0 to 7 on carbon nanotubes (CNTs)-modified platinum substrate by cyclic voltammetry in a mixture of 0.002 mol L^?1 NiSO₄, 0.25 mol L^?1 Na₂SO₄, 0.002 mol L^?1 K₃Fe(CN)₆, and 0.01 mol L^?1 aniline solutions. The morphology and structure of PANI/NiHCF nanogranules were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, respectively. The supercapacitive performances of the nanogranules were investigated with cyclic voltammetry (CV), charge/discharge tests, and electrochemical impedance spectroscopy (EIS). The results showed that the nanogranules with different morphology and sizes were obtained with the change of pH values from 0 to 7, which could control the mechanism of homogeneous or heterogeneous nucleation directly. The nanogranules were dispersed in matrix uniformly at pH 0 and pH 1, while the size of which decreased with the increase of pH values. The smooth cross-linking network structure was found from pH 2 to 7. The structure of PANI/NiHCF nanogranules had slightly changed from pH 0 to 7. PANI/NiHCF nanogranules had good electrochemical performance from pH 0 to 7 in a mixture of 0.5 mol L^?1 H₂SO₄ and 0.5 mol L^?1 KNO₃ solutions, and the highest specific capacitance value of 274 F g^?1 was obtained at current densities of 2 mA cm^?2 in neutral medium. PANI/NiHCF nanogranules had high stability in neutral medium after 2,000 cycles by CV.     

Electrochemical behaviour and determination of rimsulfuron herbicide by square wave voltammetry

The voltammeric behaviour of rimsulfuron herbicide has been studied by square wave stripping voltammetry on static hanging mercury drop electrode. It exhibited a well-defined peak within the pH range of 1.0–6.0, having a maximum peak response at ?600 mV (vs.Ag/AgCl) at pH 3.0. The factors such as accumulation potential (E_acc), accumulation time (t_acc), frequency (f), pulse amplitude (ΔE) and step potential (ΔE_s) have been optimised. The calibration plot was a straight line in the range of 4.4–134.4 μg L^?1 with a detection limit of 1.3 μg L^?1. The validity of the method was assessed from the recoveries of spiked lake water, tomato juice and agrochemical formulation of Doncep^®. The results of the experiments conducted for five recoveries were 48.8 ± 1.7 and 49.7 ± 1.0 μg L^?1, which are very close to the rimsulfuron spiked to lake water and tomato juice (50 μg L^?1), with a relative error of –2.4% and ?0.6%, respectively. The electrode reaction mechanism was also postulated.