Impact of Granular Activated Carbon on Anaerobic Process and Microbial Community Structure during Mesophilic and Thermophilic Anaerobic Digestion of Chicken Manure

In this work, the impact of granular activated carbon (GAC) on the mesophilic and thermophilic anaerobic digestion of chicken manure and the structure of microbial communities was investigated. These results demonstrated that GAC supplementation effectively enhanced the consumption of produced organic acids in the mesophilic and thermophilic batch tests, accompanied by faster biomethane production in the presence of GAC than from reactors without GAC. However, since the free ammonia level was 3–6 times higher in the thermophilic reactors, this led to the instability of the anaerobic digestion process of the nitrogen-rich substrate at thermophilic temperatures. Bacteroidia and Clostridia were the two main bacterial classes in the mesophilic reactors, whereas the class Clostridia had a competitive advantage over other groups in the thermophilic systems. The archaeal communities in the mesophilic reactors were mainly represented by representatives of the genera Methanosarcina, Methanobacterium, and Methanotrix, whereas the archaeal communities in the thermophilic reactors were mainly represented by members of the genera Methanosarcina, Methanoculleus, and Methanothermobacter. New data obtained in this research will help control and manage biogas reactors in the presence of GAC at different temperatures.

Enrichment of Homoacetogens Converting H2/CO2 into Acids and Ethanol and Simultaneous Methane Production

An anaerobic granular sludge was enriched to utilize H2/CO2 in a continuous gas-fed up-flow anaerobic sludge reactor by applying operating conditions expected to produce acetic acid, butyric acid and ethanol. Three stages of fermentation were found: Stage I with acetic acid accumulation with the highest concentration of 35 mM along with a pH decrease from initial 6 to 4.5. In Stage II, H2/CO2 was replaced by 100% H2 to induce solventogenesis, whereas butyric acid was produced with the highest concentration of 2.5 mM. At Stage III with 10 μM tungsten (W) addition, iso-valeric acid, valeric acid and caproic acid were produced at pH 4.5 -5.0. In the batch tests inoculated with the enriched sludge taken from the bioreactor (day 70), however, methane production occurred at pH 6. Exogenous 15 mM acetate addition enhanced both the H2 and CO2 consumption rate compared to exogenous 10, 30 and 45 mM acetate by the enriched sludge. Exogenous acetate failed to be converted to ethanol using H2 as electron donor by the enriched acetogens.

Temperature-Induced Precipitation of V2O5 in Vanadium Flow Batteries—Revisited

The maximum operation temperature of the vanadium solution in vanadium flow batteries is typically limited to 40 °C to prevent the damaging thermal precipitation of V2O5. Therefore, the operation of batteries at high ambient temperatures is an important aspect to tackle for stationary storage. In the present work, a comprehensive study of the high temperature stability of redox solutions for vanadium flow batteries was performed. In particular, focus was placed on a comparison between batch and in operando precipitation experiments. It was found that, despite being a widely used method in the literature, caution should be taken when assessing the precipitation through capacity fade due to the large influence of external oxidation and cycling parameters, plausibly leading to an incorrect interpretation of the results. The in operando experiments consistently show a precipitation temperature almost 10–20 °C higher than in the batch tests at a 100% state of charge for the same time lapse.

Engineering of Calcium Alginate- PANI@Sawdust Wood hydrogel Bio-beads for the Removal of the Sulfonate Groups-Containing Orange G dye from Aqueous Solution

The aim of this work is to investigate the adsorption performance of orange G (OG) dye from aqueous solutions employing PANI@sawdust biocomposite enrobed by calcium-alginate biobeads (Alg-PANI@SD). The as-prepared adsorbent was characterized by scanning-electron-microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and Fourier transforms infrared (FT-IR) spectroscopy, and used to remove Orange G dye from water. batch tests were performed as a function of adsorbent dosage, pH, contact time, interfering ions and initial OG dye concentration. Experimental results show that the kinetic model of pseudo-first-order (PFO) and Freundlich isotherm provided a good fitting of the whole experimental data. The results revealed that the as-prepared tricomposite Alg-PANI@SD, has the potential to be applied as a low-cost adsorbent for the adsorption of OG dye from aqueous media.

Recovery of Waste Polyurethane from E-Waste. Part II. Investigation of the Adsorption Potential for Wastewater Treatment

This study explored the performances of waste polyurethane foam (PUF) derived from the shredding of end-of-life refrigerators as an adsorbent for wastewater treatment. The waste PUF underwent a basic pre-treatment (e.g., sieving and washing) prior the adsorption tests. Three target pollutants were considered: methylene blue, phenol, and mercury. Adsorption batch tests were performed putting in contact waste PUF with aqueous solutions of the three pollutants at a solid/liquid ratio equal to 25 g/L. A commercial activated carbon (AC) was considered for comparison. The contact time necessary to reach the adsorption equilibrium was in the range of 60–140 min for waste PUF, while AC needed about 30 min. The results of the adsorption tests showed a better fit of the Freundlich isotherm model (R2 = 0.93 for all pollutants) compared to the Langmuir model. The adsorption capacity of waste PUF was limited for methylene blue and mercury (Kf = 0.02), and much lower for phenol (Kf = 0.001). The removal efficiency achieved by waste PUF was lower (phenol 12% and methylene blue and mercury 37–38%) compared to AC (64–99%). The preliminary results obtained in this study can support the application of additional pre-treatments aimed to overcome the adsorption limits of the waste PUF, and it could be applied for “rough-cut” wastewater treatment.

EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDIES OF ADSORPTION OF METHYLENE BLUE ON ACTIVATED CARBON FROM COCOA POD SHELLS

The aim of this research is to investigate the feasibility of using activated carbon from cocoa pod shells, waste from agriculture to adsorb methylene blue from aqueous solutions through batch tests. Various physiochemical parameters such as, contact time, initial dye concentration, adsorbent dosage, pH of dye solution and temperature were investigated in a batch-adsorption technique. The process followed the pseudo-second order kinetics model which showed chemical adsorption. Langmuir and Freundlich isotherm models were used to determine adsorption constants. The maximum adsorption capacity at 30°C is 526.31 mg/g. Thermodynamic parameters such as enthalpy change (∆Hº), free energy change (∆Gº) and entropy change (∆Sº) were studied, and the adsorption process of BM was found to be exothermic and spontaneous.

New Kinetic Turbidity Test Method and Prediction Model for Calcite Inhibition

Calcite, as one of the most common scales in oilfield can be inhibited by common scale inhibitors. The measurement of calcite nucleation and inhibition is a challenge, because of the difficulty to control pH as a result of CO2 partitioning in and out of the aqueous phase. A new kinetic turbidity test method was developed so that the partial pressure of CO2, pH, and SI can be precisely controlled. Calcite nucleation and inhibition batch tests were conducted under various conditions (SI = 0.24-2.41, T = 4-175 °C, and pH = 5.5-7.5) in the presence of common phosphonate and polymeric inhibitors. Based on experimental results, calcite nucleation and inhibition semi-empirical models are proposed, and the logarithm of the predicted induction time is in good agreement with the measured induction time. The models are also validated with laboratory and field observations. Furthermore, a new BCC CSTR Inhibition (BCIn) test method that applied the Continuous Stirred Tank Reactor (CSTR) theory has been developed, for the first time. This BCIn method was used for calcite inhibitor screening tests and minimum inhibitor concentration (MIC) estimation. By only running one experiment (< 1 hour) for each inhibitor, BCIn method selected the effective inhibitors among 18 common inhibitors under the conditions of SI = 1.23 at 90 °C and pH = 6. It was also found that the critical concentration (Ccrit) from BCIn method has a correlation with the MIC from batch tests. This study provided a simple and reliable solution for conducting calcite scale inhibition tests in an efficient and low-cost way. Furthermore, the newly developed prediction models can be used as guidance for laboratory tests and field applications, potentially saving enormous amounts of time and money.