Initial pH Of Wastewater Research Articles

Combining Activated Carbon Adsorption and CO2 Carbonation to Treat Fly Ash Washing Wastewater and Recover High-Purity Calcium Carbonate

Fly ash washing wastewater was carbonated with carbon dioxide (CO2) to remove calcium (Ca) by forming a calcium carbonate (CaCO3) precipitate. An investigation of the factors affecting carbonation showed that Ca removal was highly dependent on the initial pH of the wastewater. The Ca removal was 10%, 61%, 91% and more than 99% at initial wastewater pH levels of 11.8, 12.0, 12.5 and 13.0, respectively. The optimal conditions for carbonation were initial pH of 13.0, carbonation time of 30 min and CO2 flow rate of 30 mL/min. The Ca concentration in the wastewater decreased to <40 mg/L, while 73 g of CaCO3 precipitate was produced per liter of wastewater. However, heavy metals, specifically Pb and Zn, co-precipitated during carbonation, which resulted in a CaCO3 product that contained as much as 0.61 wt% of Pb and 0.02 wt% of Zn. Activated carbon modified by a quaternary ammonium salt was used to selectively adsorb the Pb and Zn first. The Pb- and Zn-free water was then carbonated. By combining adsorption with carbonation, the Ca concentration in the treated wastewater was decreased to about 28 mg/L, while the Na, Cl and K were retained. The wastewater thus treated was ready for NaCl and KCl recovery. In addition, the precipitate had a Ca content of more than 38 wt% and almost no heavy metals. The average particle size of the precipitate was 47 μm, with a uniform cubic shape. The quality of the precipitate met the requirements for the industrial reuse of CaCO3. In summary, adsorption and carbonation combined were able to remove pollutants from wastewater while recovering useful resources.

Energy efficient electrocoagulation using brass electrode for simultaneous nickel and chromium removal from synthetic wastewater: Cost and parametric evaluation

Electrocoagulation process using brass anode was designed for simultaneous removal of nickel (Ni) and chromium (Cr (VI)) from synthetic wastewater. In the present work, the effect of current density (Cd) 13.16–65.79 A/m2, the concentration of chromium (CC) and nickel (CN): 10–50 mg/L, pH: 2–10, Electrode distance (Ed): 0.7–3.5 cm, types of electrode material, and supporting electrolyte have been studied on the nickel and chromium removal. The brass electrode demonstrated Cr(VI) and Ni removal percentages of 99.9 % and 99.38 % respectively at concentration of Cr(VI) = Ni = 50 mg/L, Cd = 65.79 A/m2, Ed = 0.7 cm, EC time = 50 min at the initial pH of synthetic wastewater. In addition, the brass electrode demonstrated better performance with lower energy consumption (21.58 kWh/m3) and less operation cost 1.797 US$/m3) as compared to Al, Fe and Cu electrode materials.

Effects affecting ammonia removal in synthetic wastewater by locally isolated Rhodobacter sp strain A1

This research focused on the effects affecting ammonia removal in synthetic wastewater by Rhodobacter sp. strain A1 using one factor at a time method (OFAT). Rhodobacter sp. strain A1 are able to remove ammonia from synthetic wastewater due to its ability to assimilate ammonia. The ammonia removal experiment was conducted under different factors; Rhodobacter sp. strain A1 inoculum size (2%, 4%, 6%), incubation temperature (20°C, 25°C, 30°C, 37°C, 40°C), initial pH of synthetic wastewater (5,6,7,8,9) and initial NH4Cl concentration (5 mg/L, 10 mg/L, 15 mg/L) for four days of incubation period. Then, the solution was tested using Nessler reagent which will produce yellow colour when it reacts with ammonia. The intensity of colour is proportional to the ammonia concentration. This experiment was followed by ammonia quantitative analysis via spectrophotometer at 425 nm. The results obtained were then calculated to get the percentage of ammonia removal by PNSB. The result revealed that the bacterium can achieved 97.90 % efficiency of total ammonia removal at optimum growth condition with 6% of inoculum size, incubation temperature at 30°C and initial pH 7. As a conclusion, this Rhodobacter sp. strain A1 can therefore serve as a good candidate in wastewater treatment for ammonia removal.

Decolorization of C.I. Reactive Blue 78 dyeing wastewater in the chitosan-gelatin composite copper polymer/sodium persulfate system

Chitosan-gelatin composite copper polymer (CG for short) was prepared as an adsorption catalyst. The CG was combined with sodium persulfate to construct a heterogeneous Fenton-like system, which was applied to the decolorization of C.I. Reactive Blue 78 dyeing wastewater. The effects of sodium persulfate, CG, temperature, initial dyeing wastewater pH value and additives (sodium chloride, sodium carbonate) on the decolorization were investigated. The results show that the decolorization percentage of 0.1 g/L C.I. Reactive Blue 78 dyeing wastewater can reach 93.84 % under the conditions of sodium persulfate dosage of 0.3 g/L, CG dosage of 0.8 g/L, decolorization at 40 °C for 30 min. At the same time, the catalytic system has the characteristic of good decolorization effect on C.I. Reactive Blue 78 dyeing wastewater within a wide pH values range of 3–9. Even for dyeing wastewater containing 0.4 g/L high concentration C.I. Reactive Blue 78, the decolorization percentage can reach over 90 % after decolorization at 40 °C for 2 h. Moreover, CG can be reused. After repeated use of CG four times, the decolorization percentage of C.I. Reactive Blue 78 dyeing waste remains above 90 %. In addition, the weight loss rate of CG after each decolorization is less than 12 %. However, the presence of sodium chloride and sodium carbonate in the dyeing wastewater is not conducive to the decolorization of C.I. Reactive Blue 78 by the system.

The Investigation of Treatment of Pistachio Processing Industrial Wastewater by Electrochemical Methods in Terms of Chemical Oxygen Demand and Total Phenol Removal

<p>This work aims to investigate the efficiency of electrocoagulation (EC) of pistachio processing industrial wastewater (PPIW) using the continuous EC process. The tubular reactor made of stainless steel with an internal diameter of 60 mm was used as a cathode electrode. The effect of some parameters was examined on the removal of chemical oxygen demand (COD) and total phenols (TP) removal efficiency. The influences of the initial pH of wastewater (from 4 to 8), flow rate (from 25 to 125 mL/min), current density (from 7 to 21 mA/cm<sup>2</sup>), and supporting electrolyte type (NaCl, NaNO<sub>3</sub>, and Na<sub>2</sub>SO<sub>4</sub>), supporting electrolyte concentration (from 10 to 100 mg/L NaCl) on removal efficiency were investigated to determine the best experimental conditions. The examination of the physico-chemical parameters during the EC treatment showed that the best removal efficiency was obtained under conditions where the flow rate was 25 mL/min (20 min reaction time), the pH value was 5.2, and the current density was 21 mA/cm<sup>2</sup> has set. Under these experimental conditions, COD and TP removal efficiency were found to be 75% and 97%, respectively, while energy consumption was 18.5 kW h/m<sup>3</sup>. The study results show that the EC can be applied to PPIW pre-treatment.</p>

Cheese wastewater treatment through combined coagulation-flocculation and photo-Fenton-like advanced oxidation processes for reuse in irrigation: effect of operational parameters and phytotoxicity assessment.

The present study aims to investigate the efficiency of a combined cheese wastewater treatment approach involving coagulation with ferric chloride coupled with a photo-Fenton-like oxidation process for potential reuse in irrigation. Laboratory-scale tests were conducted, examining the effect of various operational parameters on the treatment process. Specifically, the effects of initial wastewater pH, coagulant dosage, decantation time for the coagulation process, and initial pH, chemical oxygen demand (COD) concentration, and Fe3+ and H2O2 dosages for photo-Fenton-like oxidation were studied. Coagulation was found effective at natural pH of 6 and showed a highest removal efficiency in terms of COD (50.6%), biological oxygen demand BOD5 (42.1%), turbidity (99.3%), and least sludge volume generation (11.8% v/v) for an optimum coagulant dose of 400mg Fe3+ L-1 and 8h of decantation time. Thereafter, photo-Fenton-like oxidation (Fe3+/H2O2/UVA-300W) of the pretreated cheese effluent enhanced the removal of COD, BOD5 and TOC to 91.2%, 91.4%, and 97.5%, respectively, using the optimized conditions (pH = 3; [Fe3+] = 5.0 × 10-4mol L-1; [H2O2] = 0.2mol L-1 and tirr = 24h). This study also shows that the proposed combined process allowed a significant phytotoxicity reduction toward lentil seed germination. The obtained outcome was encouraging and supports the possible use of the treated cheese wastewater as an additional water source for agricultural irrigation.

Highly efficient ZnO/WO3 nanocomposites towards photocatalytic gold recovery from industrial cyanide-based gold plating wastewater

Discharging the gold-contained wastewater is an economic loss. In this work, a set of ZnO/WO3 was facile synthesized by hydrothermal method in order to recover gold from the industrial cyanide-based gold plating wastewater by photocatalytic process. Effect of ZnO contents coupled with WO3 was first explored. Then, effects of operating condition including initial pH of wastewater, type of hole scavenger, concentration of the best hole scavenger and photocatalyst dose were explored. A series of experimental results demonstrated that the ZnO/WO3 nanocomposite with 5 wt% ZnO (Z5.0/WO3) depicted the highest photocatalytic activity for gold recovery due to the synergetic effect of oxygen vacancies, a well-constructed ZnO/WO3 heterostructure and an appropriate band position alignment with respect to the redox potentials of [Au(CN)2]− and hole scavengers. Via this ZnO/WO3 nanocomposite, approximately 99.5% of gold ions was recovered within 5 h using light intensity of 3.57 mW/cm2, catalyst dose of 2.0 g/L, ethanol concentration of 20 vol% and initial pH of wastewater of 11.2. In addition, high stability and reusability were observed with the best nanocomposite even at the 5th reuse. This work provides the guidance and pave the way for designing the ZnO/WO3 nanocomposite for precious metal recovery from a real industrial wastewater.

Photocatalytic Gold Recovery from Industrial Gold Plating Effluent by ZnO Nanoparticles: Optimum Condition and Possible Applications.

The comparative study of photocatalytic gold recovery from cyanide-based gold plating solution was explored via commercial and hydrothermally synthesized ZnO nanoparticles (NPs). The effects of hydrothermal temperatures on the properties and photocatalytic activities of synthesized ZnO NPs were investigated. In addition, the effects of operating parameters including types of hole scavenger, concentrations of the best hole scavenger, the initial pH of wastewater, and photocatalyst dosages were examined. The obtained results demonstrated that the commercial ZnO NPs exhibited a higher photocatalytic activity for gold recovery than that of the synthesized ones owing to their good crystal quality and the presence of non-lattice zinc ions and appropriate non-lattice oxygen ions. Via the commercial ZnO NPs, the gold ions were almost completely recovered from the cyanide-based gold plating effluent within 7 h at an initial pH of 11.0 in the presence of 10 vol % C2H5OH and 1.0 g/L of photocatalyst loading with a pseudo-first-order rate constant of 0.2637 h-1. Finally, the resultant gold-decorated ZnO NPs exhibited a higher photocatalytic property for color reduction from industrial wastewater and antibacterial activity than that of fresh ZnO NPs. The results obtained in this study possess benefits and pave the way for waste remediation and management for the plating industries.

Treatment of Textile Wastewater by a Novel Clay/TiO2/ZnO-Based Catalyst, Applying a Synergic Catalytic Ozonation–Electroflocculation Process

This study aims to investigate the treatment of real textile wastewater using a novel bentonite clay/TiO2/ZnO-based ozonation catalyst. In this study, synergic electroflocculation/catalytic ozonation, catalytic ozonation, and ozonation processes are applied in a modified hybrid reactor. To the authors’ knowledge, this is the first application of bentonite clay/TiO2/ZnO as an ozonation catalyst for treating real textile wastewater. The four operational variables—ozone dose (0.2–0.8 mg/min), reaction time (0–120 min), DC voltage supply (5–15 V), and catalyst dose (0.5–2 g/L)—were studied for decolorization and for the removal of chemical oxygen demand (COD). The results showed that the combined process (electroflocculation + clay/TiO2/ZnO/O3) had the highest removal efficiencies for COD and color (97.86% and 97.90%, respectively) at optimum parameters of 10 DC volts. an ozone dose of 0.8 mg/min, and a catalyst dose of 2 g/L in textile wastewater. The results further revealed that the initial pH of wastewater plays an essential role in the process’s overall performance. The studied synergic process was efficient for real wastewater treatment under alkaline pH (6–9). Based on empirical work, we established that the synergic process is suitable for effectively treating textile wastewater.

Evaluation of Ti/Pt Anode Efficiency and Energy Consumption in Turbidity and Suspended Solids Removal from Paper Industry Wastewater: The Effect of pH and Support Electrolyte Type

In the research, different experimental setups were used to examine the treatment of wastewater from the paper industry using the electrooxidation method, one of the electrochemical treatment methods in the batch system. In the 2000 mL volume jacketed glass reactor utilized for the treatment of wastewater from the paper industry, 4 anode and 4 cathode sieve type plates of 7 cm x 10 cm dimensions were positioned at 0.5 cm intervals, and 1200 mL wastewater was used in the tests. Coated sieve type Ti/Pt electrodes were employed as the anode in the electrooxidation studies, and uncoated sieve type Ti electrodes were used as the cathode. It was determined that the active anodic wet surface area was 1078 cm2 . The removal rates of pollutant parameters such as turbidity and SS (Suspended Solids) in the experiments; the effects of wastewater initial pH value and supporting electrolyte type parameters were investigated. According to the results, the most effective pH value for Ti/Pt anode type at 400 rpm mixing speed was determined to be waste water natural pH (7.5), and 0.50 M NaCl was the most successful supporting electrolyte type. 96.92% Suspended Solids removal efficiency and 95.38% turbidity removal efficiency for Ti/Pt anode were achieved under ideal conditions. In addition, 312.05 kW-hour/kg COD is determined as the energy consumption value.

Performance of electrocoagulation process for copper removal in simulated artisanal and small-scale mining wastewater

Electrocoagulation treatment was applied in the simulated artisanal and small-scale mining wastewater for 60 minutes. Copper concentration of 625 mg.L−1 was used in the study which was based on the real artisanal and small-scale mining wastewater (conductivity = 13 mS.cm−1, initial pH = 10) collected from Paracale, Camarines Norte, Philippines. Batch experiments using a pair of iron electrodes with an interelectrode distance of 2 cm were used for this study and we have determined the optimized conditions such as conductivity, initial pH, and current density for the various electrocoagulation runs. Decreasing initial conductivity and pH of real mining wastewater while increasing current density favours higher removal efficiency. With the conductivity of 3.5 mS.cm−1, initial pH of 9, and current density of 33.5 mA.cm−2, copper removal efficiency was 93.5%. Based on these operating conditions, energy consumption was 36.82 kWhr.m−3 and electrodes consumption were 2.09 kg.m−3. This study revealed that electrocoagulation is feasible to treat higher concentrations of copper present in mining wastewater.

Electrooxidation treatment of slaughterhouse wastewater: investigation of efficiency of Ti/Pt anode

In the present study, investigation of the applicability and efficiency of electrochemical oxidation (EO) processes for slaughterhouse wastewater (SWW) was targeted by evaluating the treatment efficiency and energy consumption values. The effects of operating parameters, such as the type of supporting electrolyte (SE) (Na2SO4, NaNO3, NaCl, and KCI), supporting electrolyte concentration (SE concentration) (0.1–0.4 M), initial wastewater pH (3–11), and current density (CD) (4.06–12.18 mA/cm2) on the removal of chemical oxygen demand (COD), suspended solids (SS), turbidity, and color were investigated. The most effective electrolyte type was observed to be NaCl. The experiment with 0.2 M SE type and 4.06 mA/cm2 current density, at a stirring speed of 400 rpm was accepted as optimum. For these conditions, it was observed that the COD, color, turbidity, and suspended solids (SS) removals were 80.05, 98.64, 99.18, and 98.47%, and energy consumption of 210.7 kWh/m3, respectively. It has been observed that the electro-oxidation process provides substantial efficiency in undesirable parameters in wastewater after 3 h of operation. Additional processes can be added to this process so that the SWW can be reused after treatment, and the recovery and further treatment of the wastewater can be achieved.

Removal and kinetics of cadmium and copper ion adsorption in aqueous solution by zeolite NaX synthesized from coal gangue.

Zeolite can remove the heavy metals in wastewater, but the removal efficiency was determined by the types of zeolites and the treatment conditions. In this study, a kind of zeolite NaX synthesized from the coal gangue, a by-product of coal production, was used and the removal efficiency of Cd2+ and Cu2+and the kinetic models were studied. The effects of its dosage, initial pH value of wastewater, and adsorption temperature on its adsorption of heavy metals Cd2+ and Cu2+ in the simulated wastewater were studied through the indoor experiments in laboratory, and the adsorption mechanism was analyzed by the adsorption kinetic model based on its adsorption efficiency and its structures. The results show that the zeolite NaX synthesized from coal gangue has a good adsorption effect on Cd2+ and Cu2+. The adsorption reaches the best effect when the dosage of zeolite is 2g/L, the initial pH of simulated wastewater is 5, the adsorption temperature is room temperature (25 ℃), and the removal efficiency of Cd2+ and Cu2+ (100mg/L) is more than 90%. Additionally, the Langmuir, Freundlich, and Temkin isothermal adsorption models were used to compare and analyze the adsorption effects. The equilibrium data was better fitted by the Langmuir model with the maximum adsorption capacities of 100.11mg/g (Cd2+) and 95.29mg/g (Cu2+), and both separation coefficients were 0-1, which shows that the process was the favorable adsorption. Weber Morris diffusion model shows that the adsorption process at 120min was more consistent with the pseudo-second-order kinetics model, and the adsorption efficiency was simultaneously controlled by the liquid diffusion step and intraparticle diffusion step. Moreover, the removal mechanism of Cd2+ and Cu2+ mainly includes physical adsorption and ion exchange. Therefore, the adsorption effect of zeolite synthesized from coal gangue is remarkable, which will provide a feasible and potential alternative for its resource application.

Comparison of sono-direct and sono-alternate current electro-coagulation processes for removal of color and turbidity from domestic wastewater

Background: Nowadays there is a problem related to wastewater handling which is released from different activities. Electrocoagulation has been a dominant treatment method for wastewater treatment. There are different forms of electrocoagulation methods for wastewater treatment. Nevertheless, there was no comparison made for the removal efficiency of the sono-alternate current (SAC), alternate current (AC), sono-direct current (SDC), and direct current (DC) electrocoagulation process. Methods: The efficiency of electrocoagulation method was compared for removal of color and turbidity from Jimma University domestic wastewater. Batch reactor DC/AC electrocoagulation cell was used to determine the removal efficiency. During the comparison, the response surface methodology (RSM) was used to analyze and optimize the data taken from the laboratory. In addition, ANOVA was used to analyze the interaction effects of different parameters. Results: The removal of color and turbidity from domestic wastewater was about 97.53% and 95.28% respectively, using direct current electrocoagulation (DCE). For alternate current electrocoagulation (ACE), the removal of color and turbidity was 98.35% and 96.12%, respectively. The removal of color and turbidity for sono-DCE (SDCE) was obtained to be 98.55% and 98.27%, respectively and for sono-ACE (SACE), the removal of color and turbidity was 99.95% and 99.76%, respectively at the optimum experimental conditions of chemical oxygen demand (COD) 960 g/L, initial wastewater pH of 6.8, the current density of 0.4 A/dm2 , inter-terminal spacing of 1 cm, and the association of electrode of Al-Al. Conclusion: According to the findings of this study, it can be concluded that, the SAC electrocoagulation method is the best and promising technique compared with all other electrocoagulation methods.

Treatment of Distillery Industrial Wastewater Using Ozone Assisted Fenton’s Process: Color and Chemical Oxygen Demand Removal with Electrical Energy per Order Evaluation

Ozonation is one of the most effective and efficient advanced oxidation processes (AOPs) and has shown great potential in the treatment of industrial effluent and wastewater. In the present work, the ozone-Fenton process for % COD and color removal together with electrical energy per order (EE/O) determination for distillery industrial wastewater (DIW) was established. The process was developed by combining the ozone (O3) with the Fenton (Fe2+/H2O2) process. The ozone-Fenton (O3/Fe2+/H2O2) was compared with other treatment processes such as O3, Fe2+, H2O2, O3/Fe2+, O3/H2O2, and Fe2+/H2O2 for EE/O together with % COD and color removal efficiency for DIW. The removal of color at 100% and chemical oxygen demand (COD) of 96.875% were achieved with a minimum of EE/O of 0.5315 kWh/m3 using the O3/Fe2+/H2O2 process by operating at optimum conditions. The % COD and color values obtained using O3/Fe2+/H2O2 were significantly higher than those obtained using O3, Fe2+, H2O2, O3/Fe2+, O3/H2O2, and Fe2+/H2O2 processes. The % color, % COD removal, and its associated EE/O were evaluated by varying Fe2+, H2O2, O3 inlet and COD concentration, and initial wastewater pH using the O3/Fe2+/H2O2 process. The synergy effect of the O3 and Fe2+/H2O2 processes was evaluated and reported. Our experimental findings suggest that combining O3 with the Fe2+/H2O2 process could effectively treat industrial effluent and wastewater.

Adsorption of chromium, copper, lead and mercury ions from aqueous solution using bio and nano adsorbents: A review of recent trends in the application of AC, BC, nZVI and MXene

Recent trends in adsorption of Chromium (Cr), Copper (Cu), Lead (Pb) and Mercury (Hg) in wastewater using (i) carbonaceous materials including activated carbon (AC) and biochar (BC), and (ii) nanomaterials including nano zero-valent iron (nZVI) and MXenes have been discussed in this paper. It has been found that adsorption capacity depends largely on the adsorbent modification technique, initial pH of wastewater, dosage of adsorbent, contact time and initial concentration of the pollutants. The pH value ranges for maximum removal of Cr, Cu, Pb and Hg have been reported as 2–4, 5–6, 5–8 and 3–8, respectively. Up to 99% removal of metals has been reported using AC, BC, nZVI and MXene. The mechanism involves the reduction and chemical adsorption of metals. AC and BC have a higher surface area (up to 5000 m2/g) compared to nZVI (up to 500 m2/g) and MXene (up to 67.66 m2/g). However, the higher reactivity and regeneration capacity of nZVI and MXene make them suitable adsorbents. From a practical point of view the application of adsorbents for real effluents, cost analysis, regeneration capability and reuse of heavy metals are some aspects that need attention in future studies. The removal efficiencies of AC and BC are comparable to the nZVI and MXene. The cost analysis may be an attractive aspect to decide the future application of these adsorbents at large scale.

Investigation of turbidity removal and energy consumption from pistachio processing industry wastewater by electro-oxidation process

ABSTRACT. In this study, it was aimed to remove turbidity, which is an important parameter of water quality, and to examine energy consumption from pistachio processing industry wastewater (PPIW). As working parameters, mixing speed, supporting electrolyte (SE) type and concentration, initial pH value of wastewater, and current density were examined. Graphite was used as the anode material, and stainless steel was used as the cathode material. The highest removal for the mixing speed parameter was achieved at 400 rpm, the maximum efficiency for the SE type was achieved at NaCl, a concentration of 2 M for the SE concentration, a pH of 3.0 for the wastewater initial pH value, and a current density of 30 mA/cm2. However, considering the energy consumption cost in these parameters, the optimal conditions were determined as 1.25 M of SE, pH 3.0, mixing speed of 400 rpm, and current density of 6 mA/cm2. In these conditions, the turbidity removal efficiency was found to be 90.61%. Energy consumption for the same conditions is calculated at 180 kWh/m3. In the results obtained, it is observed that energy consumption decreases as the concentration of SE increases. NaCl, which is the electrolyte that provides maximum efficiency in removing turbidity, is also the electrolyte that provides minimum energy consumption. In electrochemical systems, the cost is as important as lifting efficiency. Therefore, the choice should be made, considering which of these two parameters will be the priority.
 
 KEY WORDS: Electro-oxidation, Turbidity removal, Graphite anode, Wastewater treatment
 
 Bull. Chem. Soc. Ethiop. 2022, 36(1), 223-234. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i1.18

A Clean Method for Vanadium (V) Reduction with Oxalic Acid

Water pollution deteriorates ecosystems and is a great threat to the environment. The environmental benefits of wastewater treatment are extremely important to minimize pollutants. Here, the oxalic acid used as reductant was used to treat the wastewater which contained high concentration of vanadium (V). Nearly 100% of vanadium was efficiently reduced at selected reaction conditions. The optimization results simulated by response surface methodology (RSM) analysis indicated the parameters all had significant effects on the reduction process, and followed the order: dosage of oxalic acid > reaction temperature > reaction time > initial pH of vanadium-containing wastewater. The reduction behavior analysis indicated that the pseudo first-order kinetics model could describe well the reduction process with Ea = 42.14 kJ/mol, and was described by the equation as followed: −LnC=K0·[pH]0.1016·[n(O)/n(V)]2.4569·[T]2.2588·exp(−42.14/T)·t.

Degradation of 2-Naphthol in Aqueous Solution by Electro-Fenton System with Cu-Supported Stainless Steel Electrode

For the treatment of 2-naphthol wastewater, the homogeneous electro-Fenton process was considered as an effective method but some disadvantages greatly restrict its application. The three-dimensional electro-Fenton (3D-EF) system using a nano zero-valent iron-supported biochar (NZVIs-BC) particle electrode and a Cu-supported stainless steel electrode (Cu-SSE) was proposed to avoid the disadvantages of the homogeneous electro-Fenton. In this work, the 3D-EF system was developed, which consisted of a Cu-SSE (cathode), a graphite rod (anode) and a NZVIs-BC particle electrode. The effect of the ratio of ferrous sulfate heptahydrate (FS) to rice straw (RS), CuSO4•5H2O amount, initial pH of 2-naphthol wastewater and current intensity (the output current of the power supply) on the removal rate of 2-naphthol were investigated. It is noteworthy that more than 98.36% of the 2-naphthol in aqueous solution was removed by the 3D-EF system, and only about 60.09% of 2-naphthol was removed by the homogeneous electro-Fenton system. Furthermore, naphthalene, benzoic acid, β-naphthoquinone, 1, 2-naphthalenedione, phenol and aromatic hydrocarbon were the main degradation products of 2-naphthol by the 3D-EF system; the toxicity of 2-naphthol wastewater was also greatly reduced.

Treatment of organic wastewater by ozone in a continuous rotating solid foam stirrer tank

The work herein employed a novel rotating solid foam stirrer tank (RSFST) under continuous operation in attempt to intensify ozone-liquid mass transfer rate and possibly enhance treatment of organic wastewater. P-nitrophenol (PNP) and acid red B (ARB) were separately used to simulate phenolic and dye wastewater. Results show that the removal efficiency of PNP and ARB dye increased with increasing rotational speed and gas flow rate but decreased with increasing liquid flow rate and initial wastewater concentration. The highest removal efficiency of PNP and ARB was attained at pH of 11 and 7, respectively. Ozone utilization efficiency increased with increasing stirring speed, liquid flow rate, initial wastewater concentration and pH but decreased with increasing gas flow rate. The treatment efficiency of organic wastewater in the RSFST reactor is superior to that of many other reactors (rotating packed bed and bubble column, etc.). Correlations to predict the removal efficiency of the organics were developed and the deviation between the experimental and predicted values is within 15%, indicating that the correlations can be used to predict the removal efficiency of PNP and ARB by ozone in RSFST. The study provides a scientific reference for development of a new high-efficiency ozone oxidation reactor.