One of the major difficulties in the assessment of costs of desalination projects is that key investment parameters and operation-related parameters are project-specific data. This information is commonly not in the public domain and is generally available only to the general contractor. In addition, the interpretation of published data is complicated by the fact that often plant boundaries are not clearly indicated (e.g. if the intake cost and the pipeline cost to and from the plant are included in the evaluation). Finally, the analysis involves an elevate number of design parameters, such as plant capacity and configuration, metal and other material prices, and very site-specific conditions (seawater quality, feed water intake, and brine discharge). In the end, these issues result in difficult comparability of data from different sources about the cost of the desalinated water. This paper deals with the implementation of a flexible techno-economic model for the assessment of desalination plants on system analysis level. Thereby, the focus is given to units driven by different technologies (conventional steam turbines and concentrating solar power). The model is applied in a case study in order to evaluate and compare the performance and the costs of different desalination technologies (multiple effect distillation and reverse osmosis). Finally, a sensitivity analysis of the results with respect to selected key design parameters is carried out.
Areas in many rural and costal zones, particularly in developing countries, have a demand for a lower-price, low maintenance, environmentally friendly, and decentralized small-scale desalination systems. For these regions, a new thermal desalination system with heat recovery has been developed and tested in different countries. The system has two components: a desalination tower with multiple stages and a set of solar thermal collectors. Sea and ground water can be fed on the top stage of the tower, and it flows down filling the lower stages. The tower produces desalinated and decontaminated water in its 5–7 horizontal stages. The present work presents the field results of two systems tested in Brazil, and the numerical results of a design installation for Namibia. For Namibia, six systems are planned with capacity of 400–500 L/d. Seven systems use flat plate collectors and tree systems use evacuated tube collectors. In Brazil, two systems with a 35–40 L/d capacity, one with evacuated tube and the other flat plate collectors were tested. They incorporate the most recent improvements made in the components so far. The performance was evaluated by the coefficient of performance and the gain output ratio values. They were 4.78 and 2.52 for the field tests in Brazil. The simulated values for Namibia were 72 L/d for a 4.4 m solar collector area and 1.5 m condensation area per stage.
In this study, decolorization of Acid Blue 113 textile azo dye (AB 113) by a bio-Fenton process has been performed in an aqueous medium. The bio-Fenton oxidation process tested is the oxidation process of glucose for H2O2 generation and in situ use of H2O2 with Fe2+ as Fenton reagents to produce hydroxyl radicals which degrade the organic dyes. The effect of different parameters such as AB 113, glucose, FeSO4 concentrations, and also the glucose oxidase activity on the decolorization of AB 113 dye was assessed. Artificial neural network was used to simulate the decolorization of AB 113 aqueous solution. Different networks were designed for this process. The best network was 5-14-1 due to the best coefficient of determination (0.996) and mean square error (0.42). The results indicated that ANN is provided reasonable predictive performance.
An assortment of equilibrium assessments was conducted at 298 ± 2 K with a granulated resorcinol-formaldehyde (RF) resin, and acetone resorcinol formaldehyde gel (ARF) in an attempt to decontaminate 134CS from waste streams. A: R: F: Na2Co3 was optimized as 2:1:2:1.6, during ARF preparation while, R: F: Na2Co3 was found to be 1: 3.5: 1.5 in case of RF, respectively. The obtained gels were amorphous and possessed different functional groups. The ARF had higher surface area and total pore volume values than RF; 780 m2/g and 0.62 cm3/g were the maximum values obtained for ARF under different conditions. The scanning electron microscope graphs proved that they are granular and spherical in nature with nanometer sizes under 22 W ultrasonic dispersion. In these tryouts, simulated waste sample to134Cs was used in comparison with other radioactive 60Co and 152+154. Lagergren first-order kinetic model was used to compare the kinetic constants, K ads of the tested ions; the order of K ads of Cs+ 2+ 3+, which were in accordance with data obtained in the Cartesian coordinate in space. However, a reversed order of selectivity and capacity measurements was obtained because of hydration of the ions in solution.
The present study investigates the photocatalytic degradation of C. I. acid red 14 (AR 14) as a textile dye, in aqueous medium using immobilized TiO2 nanopowder on glass beads illuminated by a UV-C lamp (30 W). Photocatalytic degradation of organic pollutants is done with photogenerated holes as a result of UV light irradiation on surface of TiO2 nanoparticles and generation of hydroxyl radicals as power oxidant. This process is performed under a set of variables (concentration of peroxydisulfate, AR 14, and temperature). AR 14 photocatalytic degradation increased with increasing peroxydisulfate concentration and temperature. The increase in dye concentration caused a decrease in removal efficiency. The progress of photocatalytic decolorization of the AR 14 was studied by measuring the absorbance at λ max = 514 nm by UV–Vis spectrophotometer. The results indicated no observable loss of the color when the UV or UV/TiO2 was applied in the absence of [Inline formula]. The results reveal that a considerable decrease in the concentration of the dye occurs when the sample was photocatalytic degraded by [Inline formula].
In this paper, batch removal of diazinon and 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solution by granular-activated carbon was investigated. The required concentrations of toxins were prepared by appropriate dilution of the stock standard solution. There was a significant relationship between chemical oxygen demand (COD) and toxins concentration and that COD was measured instead of direct analysis of toxins. For all the concentrations tested, removal efficiency increased by increasing contact time for both toxins. The highest removal efficiency of 90% for 2,4-D and 88% for diazinon obtained in 50-min contact time. The highest value of toxin removal for both toxins occurred at pH=6. Based on the results obtained, one can conclude that granular-activated carbon has high efficiency in 2,4-D and diazinon removal from aqueous solution.
2,4,6-Trinitrotoluene (TNT) is toxic and mutagenic to many living organisms, so more and more rigorous limits on the letting amount of TNT have been established. In this paper, monomer vinyl acetate (VAc) is grafted step by step on the surface of silica gel particles, and the grafted particle PVAc/SiO2 is formed. Then, the novel adsorbent polyvinyl alcohol (PVA)/SiO2 possessing strong adsorption ability for TNT is obtained through the alcoholysis reaction of PVAc. The grafted particles PVAc/SiO2 and PVAc/SiO2 are characterized by Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). The adsorption performance of PVA/SiO2 toward 2,4,6-trinitrotoluene (TNT) is investigated through static methods. The experimental results show that PVA/SiO2 possesses strong adsorption ability for TNT with adsorption amount of 18.21 mg g−1. The empirical Freundlich isotherm is also found to agree well with the equilibrium adsorption data. In addition, pH is found to have great influence on the adsorption amount. Finally, PVA/SiO2 is found to have excellent reusability.
The decoloration and mineralization of the azo dye, Acid Blue 29 (AB 29) in aqueous solution was investigated in the presence and absence of air by Fenton and Fenton-like processes using hydrogen peroxide (HP) and sodium persulfate (SPS), respectively, as oxidants. The effect of various operational parameters and presence of [Inline formula], [Inline formula], [Inline formula], and [Inline formula] ions on the decoloration was examined. Higher decoloration was observed at pH 3 and 5 in both the cases. On the basis of mineralization efficiency (34.1 and 28.5%, respectively, with HP and SPS in 180 min), it was concluded that HP is a better oxidant than that of SPS. The decoloration in the absence of air is decreased until a certain time period, beyond which it increases and becomes same as that in the presence of air. This is explained on the basis of in situ generation of HP and peroxyl radicals. Although all ions under study inhibit decoloration significantly, the inhibition efficiency of [Inline formula] is less than that of others.
In this research, the gold (Au) nanoparticles loaded on activated carbon (Au-NP-AC) have been applied for the removal of Acid Red 299 (AR-299). The influence of variables, including the pH, AR-299 concentration, amount of Au-NP-AC, contact time, and temperature in a batch method, on the AR-299 removal has been investigated. Following the optimization variables, by fitting the experimental equilibrium data to Langmuir, Freundlich, and Tempkin, the respective information for each model and their applicability to understand the concept of adsorption was examined. According to R 2 and error analysis, it was found that the adsorption process follows the Langmuir model. It was found that among various kinetic models, such as first- and second-order, Elovich, and intraparticle diffusion model, the experimental data at various removal times was interpreted using the second-order kinetic model with the involvement of the intraparticle diffusion model. The negative value of Gibbs free energy and the positive value of the adsorption enthalpy show the spontaneous and endothermic nature of the adsorption process.
The inhibitive and adsorptive characteristics of ethanol extract of fennel seeds for the corrosion of 304 stainless steel (SS) in 1 M HCl solutions have been studied using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy, and electrochemical frequency modulation methods for monitoring corrosion. Ethanol extract of fennel is a good adsorption inhibitor for the corrosion of 304 SS in HCl. The inhibitive property of the extract is attributed to the presence of anethol and fenchone as major constituents in the extract. Inhibition efficiency increased with increasing concentration of the extract but decreased by increasing the temperature. Adsorption studies revealed that Langmuir adsorption isotherm is the best adsorption model applicable to the adsorption of fennel extract on 304 SS surface. Activation and adsorption parameters were evaluated and discussed. Potentiodynamic polarization measurements indicated that the inhibitor is of mixed type. The results obtained from these techniques were in good agreement to prove the validity of these tools in the measurements of the tested inhibitor.
This study deals with the extraction of salicylic acid (SA) from aqueous solutions through a flat-sheet supported liquid membrane system. Tricaprylmethylammonium chloride (Aliquat® 336) diluted in 2-octanol is used as membrane organic phase. In a previous work, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim][PF6]) or ethylammonium nitrate (EAN) is used instead of the above mixture. Transport efficiency around 50% and 9 days stability has been obtained. In this work, the use of 10% (v/v) Aliquat® 336 in 2-octanol improves the transport efficiency of the system (around 90%). The important operational variables affecting the facilitated transport of SA are concentration of Aliquat® 336, membrane viscosity, feed phase pH, stripping agent concentration, initial SA concentration, polymeric support type, and membrane stability. Regardless of its higher SA transport efficiency, the SLM based on the mixture Aliquat® 336/2-octanol exhibits shorter long-term stability (time dependent-negative tendency) as compared to the use of [C6mim][PF6] or EAN.
In the present paper, extraction procedure for copper (II) present in an aqueous sulphate media using a supported liquid membrane by chloride tri-n-octylmethylammonium (Aliquat 336) and Tri-n-butylphosphate from molar ratio 1:1, with polytetrafluoroethylene as a membrane support was studied. The effects of various parameters such as initial pH, potassium thiocyanate concentration and ammonium acetate concentration on the extraction yield, were carried out. By a calculation programme using Chemical Equilibrium in Aquatic System V. L20.1, the determination of the percentages of the present species before and after extraction were given in aqueous medium and on the membrane to be able to determine the relation between the nature of the extracted species and the extraction yield. The optimization process was carried out using 23 factorial designs. Initial pH (pHi) of feed solution, the concentration of potassium thiocyanate and the concentration of ammonium acetate were regarded as factors in the optimization. Student’s t-test on the results of the 23 factorial design with eight runs for copper (II) extraction demonstrated that the factor concentration of potassium thiocyanate in the levels studied are statistically significant. Under the optimum conditions the percentage of extracted copper (II) was 93.6% in one step.
In this work Central Composite Design (CCD) based on Response Surface Methodology (RSM) was employed to evaluate the effects of operational parameters (reaction time, initial dye concentration, initial H2O2 concentration and distance of UV lamp from the solution) affecting photooxidative decolorization of a dye solution containing C.I. Basic Red 46 (BR46) and for optimization of the process. Predicted values were found to be in good agreement with experimental values (R2 = 98.92% and Adj-R2 = 97.79%), which indicated suitability of the model employed and the success of CCD in optimizing the conditions of UV/H2O2 process. Graphical response surface and contour plots were used to locate the optimum point. The results of optimization predicted by the model showed that maximum decolorization effi ciency was achieved at the optimum condition of reaction time 14 min, initial dye concentration 20 mg/L, initial H2O2 concentration 1.0 g/L and 16 cm distance between UV lamp and the solution. In addition, a mathematical relation between the apparent reaction rate constant and used H2O2 was applied for prediction of the photooxidative decolorization rate constant (k). The results indicated that this kinetic model provided good prediction of the k values for a variety of conditions. The Figure-of-merit electrical energy per order (E Eo) was employed to estimate the electrical energy consumption.
The nanoscale zero valent iron (NZVI) and ordered mesoporous molecular sieve Mobil Composition of Matter No. 48 (MCM-48) composite material (NZVI–MCM-48) were prepared by the hydrothermal treatment at 120°C for 36 h and then drying at 100°C of synthetic solution with a mole ratio of silica, cobalt, cetyltrimethylammonium bromide (CTAB), sodium hydroxide, sodium fluoride, and water is l:0.01:0.65:0.5:0.1:71 to get the NZVI–MCM-48 raw powder which was then treated by roasting in a nitrogen atmosphere to release the surfactant and by high temperature carbonization and reduction. The existence of NZVI in the composite material and its orderliness, form, and element composition were analyzed by characterization means such as X-ray diffractometer (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The orthogonal degradation experiment for treating methylene blue (MB) wastewater by the composite material led to a 853 mg/g decolorization rate of MB and a 821 mg/g chemical oxygen demand (COD) removal rate under the optimal conditions including an initial concentration of wastewater of 10 mg/L, an initial pH of 6, a concentration of the added sample of 0.8 g/L, and a reaction time of 60 min. The degradation mechanism for MB wastewater is also discussed.
Performic acid (PFA) is an oxidizing agent which has recently attracted attention its for use as disinfectant in the medical field and food industry. This study investigated the efficacy of PFA catalyzed by both sulfuric and ascorbic acid. Tap water in one experiment and sterilized activated sludge effluent (ASE) in another, were used for the preparation of aqueous solutions. Escherichia coli was used as the target micro-organism to investigate the efficacy of catalyzed PFA. The results were analyzed to set up the pertinent mathematical relationship according to Hom’s model. Applying the highest initial dose of 15 mg l−1, showed the superior catalytic action of sulfuric acid and 7-log inactivation was achieved in 30 min of disinfection period. Application of PFA on E. coli in our experiment caused CT value of 12.16 mg min l−1 for 99% inactivation and CT value of 23.82 mg min l−1 for 99.9% inactivation. PFA produced 4-log inactivation at a CT value of 35.48 mg min l−1. The results showed that, the promoting action of sulfuric acid is expected in higher initial dose of PFA when synthetic liquid medium was prepared of sterilized ASE. The disinfection efficacy of PFA is proved to be less than free chlorine and more than chloramines.
Photocatalytic decoloration of Acid Yellow 99 dye by TiO2 has been investigated under different experimental conditions. Addition of β-Cyclodextrin on TiO2 enhanced the photoactivity of TiO2 in AY99 degradation. Optimal experimental conditions on catalyst amount, pH value, illumination time, and dye concentration have been determined. The mineralization of AY99 has been confirmed by Chemical Oxygen Demand measurements. The higher photoactivity of TiO2-β-CD/visible light system than TiO2/visible light system can be ascribed due to the ligand to metal charge transfer from β-CD to TiIV located in an octahedral coordination environment. The complexation patterns have been confirmed with UV–Visible and FT-IR spectral data. The interactions between TiO2 and β-CD have been characterized by Field Emission Scanning Electron Microscopy, X-ray powder diffraction analysis, and UV–Visible diffuse reflectance spectroscopy.
Municipal wastewater treatment suffers the general problems of poor denitrification and low phosphorus removal caused by insufficient carbon sources. Thus, a baffled reactor was developed to provide additional carbon by hydrolysis and acidification of the primary sludge in the A2/O process in order to treat low C/N ratio wastewater. The effects on denitrification and phosphorus removal were evaluated. The results showed that CTN, CTP, CCOD, and [Inline formula]-N in the effluent were concentrated at 17, 0.5, 30, and 1.6 mg/L, respectively, while the removal efficiencies rose to 69.6, 92.5, 88, and 96.7%, respectively, while dosing acidified primary sedimentation sludge. Compared with control groups that did not receive acidification liquid, CTN, CTP, and [Inline formula]-N of the effluent were decreased by 8.7, 1.3, and 0.7 mg/L, respectively, and the removal efficiencies were correspondingly increased by 15.6, 22.5, and 1.7%, respectively. These data demonstrated that adding acidified primary sludge effectively improved the removal of nitrogen and phosphorus nutrients.
Based on the successful adoption of A2O membrane bioreactor (MBR) system with 2.5 times treatment capacity (5,000 m3/d) rather than conventional activated sludge process (2,000 m3/d), A domestic wastewater treatment plant in the northwestern China was greatly upgraded that can effectively meet the requirements of wastewater treatment and reclamation. In the A2O process, with high-depth aeration (11.0 m), high organic and ammonia nitrogen removals were achieved synchronously in a wide range of sludge retention time. This system could be also strategically controlled to achieve high-phosphorous removal by optimized discharge of excess sludge. This project provided the first case study of A2O MBR system in the cold region and showed the advantages of membrane technology for water reclamation in water-deficient areas of China.
Nitrogen removal was studied in a pilot-scale anaerobic–anoxic–oxic (AAO) system that was bioaugmented with nitrifiers cultivated from reject water after seasonal deterioration. The process of nitrogen removal was evaluated with increased temperature from 11 to 24°C. Nitrification efficiency rapidly recovered with increased temperature from 12 to 15°C, and the nitrification rates at 18°C were 3.1 times that at 12°C, higher than the report in ASM1. Bioaugmentation may shorten the recovery time of nitrification activity in WWTPs. The nitrification activity and microbial ecology of the full-scale system operating parallel with the pilot-scale were correspondingly studied, and similar community structures were observed. Despite the lower nitrifying bacteria count, the nitrification activity of the bioaugmented pilot-scale plant was still higher than that of the full-scale one.
The mechanism of bacteria abatement during an electrocoagulation treatment was investigated with the soluble aluminum electrodes on Escherichia coli cultures in model solutions. The efficiency of E. coli abatement was established under two kinds of experiments: in a 1 L batch reactor and in a 10 L pilot reactor with flowing solution. About 97% of abatement was obtained after 35 min with a current intensity of 0.22 A. Electrocoagulation exhibited greater bacteria abatements by a 2-log factor than for a chemical coagulation using identical quantities of aluminum. The decanted flocs of electrocoagulation were analyzed by X-ray diffraction which showed that electrogenerated alumina contained nanocrystallites of boehmite AlOOH. Moreover, these flocs contained living bacteria. This observation suggests that bacteria removal during electrocoagulation could be attributed to a strong bacteria adhesion on the surface of electrogenerated alumina particles followed by a separation of the decanted solids. The abatement of E. coli by electrocoagulation was the result of concomitant processes: mortality due to depletion of oxygen and nutrient species and adsorption on alumina and sedimentation. Redox potential measurement showed that during electrocoagulation the solution was not oxidizing and that E. coli removal can not be attributed to chlorine formation. The electrocoagulation treatment led to bacteria removal but it was not a true disinfection process.
A sensitive and simple method for the simultaneous preconcentration and extraction of trace amounts of Cd2+, Co2+, Cu2+, Ni2+, and Pb2+ ions in some real samples without using organic solvent has been reported. The method is based on the adsorption of these metal ions on 4-(2-Pyridylazo) resorcinol (PAR) loaded on activated carbon (AC). The retained analytes on modified activated carbon were eluted using 3.0 mL of 3.0 mol L−1 nitric acid. The influences of the various analytical parameters including pH, amount of sorbent, sample volume, and eluent type on the recovery efficiencies were investigated. The experimental data were fitted to different conventional isotherm models including Langmuir and Freundlich isotherm. Generally, Langmuir model was found to represent the experimental isotherm data better than Freundlich model. The paper discusses the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy). Our results demonstrate that the adsorption process was spontaneous and exothermic. The effects of interference ions on retentions of the analytes were also examined. The recoveries of analytes were generally quantitative with a relatively low RSD. The method has been successfully applied for these metal ions content in some real samples.
Preparation of activated carbons from bio-solid is a promising way to dispose bio-solid as well as to produce a low-cost adsorbent for pollutant removal. Various physical and chemical processes are in use for the activation of the activated carbon derived from bio-solid (ACBS). Both physical and chemical characterizations provide fundamental knowledge for its potential application for pollutants removal. The literature illustrates that KOH, the chemical activation procedure is found to be the most effective technique for producing high BET surface area ACBS, with areas in excess of 1,882 m2/g being reported. In this review, the results reveal that the ACBS is comparable with commercially activated carbons.
Excess sludge is difficult to be processed and it is hydrolytically degraded under both anaerobic and aerobic conditions, since a high proportion of the sludge comprise living micro-organisms. The key phenomenon that occurs during the process of disintegration of sewage sludge is destruction of cell walls in micro-organisms caused by physical, chemical or biological factors. Consequently, sludge is fragmented and some intracellular components are released into the surrounding liquid. In order to determine the best parameters of acid disintegration of excess sludge, the study examined the effectiveness of oxidizing treatment with peracetic acid. STERIDIAL W 15 solution, which is a mixture of PAA (15%), hydrogen peroxide (10%), acetic acid (36%) and water (39%) was used in the study. Pre-treatment in the ambient temperature prior to the period of 1 and 24 h was conducted. The doses of peracetic acid of 0.1–5 mL of STERIDIAL/L of excess sludge were used (as for the organic dry matter content corresponds to the about 0.01–0.66 mL of STERIDIAL/g dmorg.). The volatile fatty acid and COD levels obtained after acid pre-treatment of excess sludge were corrected by taking into account the value of those parameters originating during the PAA hydrolysis in the water surrounding. For non-pre-treatment and undergoing chemical modifications of the sludge, the organic dry matter content was 7.56 g/dm3. In the case of non-pre-treatment sludge, the value of volatile fatty acids 51 mg CH3COOH/L was recorded. During the chemical disintegration lasting 24 h, volatile fatty acids content of 171 mg CH3COOH/L and 5734 mg CH3COOH/L was obtained, respectively, for the low dose i.e. 0.1 mL of STERIDIAL/L of sludge and the highest dose i.e. 5 mL of STERIDIAL/L of sludge. The value of chemical oxygen demand (COD) for non-pre-treatment and chemically conditioned sludge after using the above doses amounted, respectively, to 102, 222 and 5432 mg O2/L. The content of volatile fatty acids correlated with the observed level of COD.
This paper investigated the accumulation of arsenic and its chemical fraction distributions in a low-sludge wastewater treatment system using “sonication-cryptic growth” method. Subsequent bio-reactors (SBR) were used; one SBR without sonication was used for control. Results showed that “sonication-cryptic growth” technique cut sludge production in SBR by 50%. The accumulation of arsenic in sludge occurred in both reactors; the accumulation was low in 0–60 days and showed a sharp increase in 60–90 days. The final sludge arsenic content in the low-sludge system was 1.23 times of that in the control system. However, the higher arsenic content in the low-sludge treatment system did not impact the COD removal and the sludge bioactivity. The low-sludge system had higher COD removal efficiency and higher sludge activity than those of the control. Further analyses of the chemical fraction distribution of arsenic showed that arsenic existed in different forms in the two systems. In the control system, the major form of arsenic in sludge was the organically bound fraction during 0–60 days, and the chemical fractions were redistributed during 60–90 days and the Fe/Mn oxide fraction and organically bound fraction were the main fractions. In the low-sludge system, the major form of arsenic in sludge was Fe/Mn oxides bound fraction during the whole operation duration.
Water pollution of volatile organic compounds (VOCs) was a serious environment problem. Vacuum membrane distillation (VMD) was an environmental friendly membrane separation technology to treat VOCs wastewater. Aqueous binary mixtures of ethyl acetate were treated by VMD process. Comparisons were made between different membrane modules for investigating the influence of channel on the membrane separation performance. Three kinds of channel presented different useful area, shape, width, and depth. The arc flow channel was more easier to reduce resistance than square flow channel. Operation parameters influencing flux and separation performance were examined: feed-flow rate, feed concentration, vacuum degree, and feed temperature. Vacuum degree and feed temperature had more significant influence on membrane flux and separation factor than other parameters. The effect of membrane type on separation properties was also investigated, the smaller pore membrane was better for increasing the separation factor. Three membrane modules with various channels were used for experiments. VMD is very suitable for low concentration of aqueous solution VOC separation and better experimental separation performance could be obtained.
In this work, kinetic and mechanistic study of photochemical degradation of 4-chlorophenol (4-CP) with UV lamp of 6 W, 12 W, 18 W, and peroxy acetic acid (PAA) oxidant was estimated. The differential method was evaluated by fractional order of reaction for both UV and UV/PAA processes. Overall and initial reaction rate constants were evaluated using integral method. Reaction rate increases with UV input and PAA concentration and it decreases with the increase in 4-CP concentration. Samples were analyzed by HPLC, UV spectrophotometer, and GC-MS for residual concentration and identification of degraded products. The degradation compounds are identified and probable mechanism of reaction is established.
In this study, treatment of grease and oil (G&O) and other impurities in waste glycerol from biodiesel production was performed by a two-step process, by acidification and the coaleser process. 1 M hydrochloric acid (HCl) was used to acidify waste glycerol to destabilize the emulsion and remove the suspended solids (SS), soap and methyl ester. For acidification, a pH of 6 was selected, before testing with coalescer. The study was investigated with a wide range of factors and parameters including two media materials (polypropylene (PP) and polyethyleneterephthalate (PET)), two configure shapes (granular and fiber), pH (3–6), bed height (50–150 mm), and flow rate (5–18 dm3/h). The results of the study in the same experiment conditions showed, PP media material gave better results than PET media materials where the fiber sharp material performed better than the granular sharp material. G&O concentration of treated waste glycerol reduced to 0.081 g/L under operating conditions with 120 mm bed height, 5 dm3/h flow rate and PP fiber media.
In the conducted research, corncob powder was pretreated with inorganic acids and bases. The consequence of different parameters such as initial metal concentration, pH, and contact time on Zn(II) biosorption from aqueous solution was deliberated. The order of maximum Zn(II) uptake q max (mg g−1) for different pretreated and raw corncob powder was Ba(OH)2 (128.9) > H3PO4 (124.07) > NaOH (118.737) > H2SO4 (114.8) > HCl (93.41) > Al(OH)3 (87.9) > Native (86.74). The percentage of Zn(II) removed on corncob biomass increased with increase in pH reaching a maximum at pH 5.5. Kinetics of Zn(II) biosorption described that Zn(II) sorption rate was high in first 15–30 min and equilibrium was established after 120 min. The maximum adsorption data of native and pretreated biomass was investigated using Langmuir, Freundlich equilibrium, and Pseudo-first and second-order kinetic models. It was accomplished that structural modifications onto corncob powder lead to the formation of novel biomasses with increased sorption efficiency and environmental stability for the abatement of Zn(II).
The O-phenylacetyl β-CD derivative 1 was obtained by substitution of β-CD and characterized by spectroscopic methods. Competitive transport of equimolar mixtures of Pb(II), Cd(II), Cu(II), and Na(I) ions from aqueous nitrate feed phase across polymer inclusion membranes (PIMs) using O-phenylacetyl β-CD 1 derivative as an ion carrier has been investigated. The influence of the phenylacetyl groups attached to β-CD rings on the selectivity and efficiency of metal ions transport across PIMs containing cellulose triacetate (CTA) as the support was studied. The efficiency of a membrane for the selective transport of Pb(II) ions has been investigated, and several parameters affecting metal transport have been evaluated, such as the carrier concentration, the plasticizer content, and the acidity of the aqueous phase. We found that facilitated transport of metal ions across the above PIMs proceeds via a carrier-mediated mechanism and is dependent on pH-driving force. PIMs including 1 selectively transported Pb(II) ions at concentration of ion carrier in membrane equal to 0.6 M and have shown the preferential selectivity order: Pb(II) >> Cd(II) > Cu(II) > Na(I). The repeated transport experiments of PIM indicated the long-term integrity of PIM.
A novel superabsorbent hydrogel based on poly(acrylic acid-sodium acrylate-acrylamide)/sodium humate poly(AAc-SA-AM)/SH was applied as adsorbent to adsorb metal ions (Pb2+, Fe2+) from the aqueous solutions. The factors affecting adsorption capacity of the poly(AAc-SA-AM)/SH hydrogel such as contact time, pH, temperature, SH content (wt.%), initial concentration of the metal ion, and ionic strength were systematically investigated. Results from the experimental data revealed that an appropriate addition of SH (2.44 wt.%) not only increases the metal ion adsorption of poly(AAc-SA-AM) hydrogel but also improves its regeneration ability. The results showed that the adsorption equilibrium data fitted the Langmuir isotherm better than the Freundlich isotherm. The maximum binding capacity for Pb2+ ion was 198 and 164 mg/g/l for Fe2+ ion for per g of poly(AAc-SA-AM)/SH (SH4) hydrogel (high as compared to many other adsorbents). The changes in thermodynamic parameters were also calculated, and the negative ΔG° and ΔH° confirmed that the adsorption process was spontaneous and exothermic. The kinetic studies revealed that the adsorption process can be well described by the pseudo-second-order kinetic model.
This paper describes the studies on the partitioning of actinides from high-level liquid waste of PUREX origin employing supported liquid membrane technique. The process uses solution of tri-n-octyl phosphine oxide in n-dodecane as a carrier with polytetrafluoroethylene support and a mixture of citric acid, formic acid and hydrazine hydrate as a receiving phase. Transport of 241Am has been studied as a function of various parameters such as acidity of feed, concentration of carrier, effect of uranium concentration, effect of trivalent ions and salt concentration in the feed in order to optimize efficient transport conditions. The studies indicated good transport of actinides like uranium, neptunium, plutonium and americium across the membrane from nitric acid medium. Under the optimized conditions, the transport of 241Am is also studied from a uranium-depleted synthetic pressurized heavy water reactor-high-level liquid waste (HLLW). Also the technique has been used for the partitioning of alpha emitters from research reactor-HLLW.
The removal of typical s-triazine herbicides including atrazine, simazine, and prometryn by granular activated carbon were studied under different temperatures (5, 10, 15, 25, and 35oC) and different water (distilled water, tap water, and river water). The results showed that the adsorptions of s-triazine herbicides in different. The adsorption of s-triazine is the greatest in distilled water and that is smallest in natural water. Moreover, for the adsorption isotherm, Freundlich model fitted the adsorption of s-triazine herbicides better than Langmuir model and the adsorptions of prometryn is the greatest, then that of atrazine and that of simazine is smallest.
The differences in the adsorption/desorption behavior of benzene, toluene, ethyl-benzene, and p-xylene (BTEX) using rice husk activated carbon (RHAC) were studied. It was proved that RHAC were quite effective in removing BTEX compounds from aqueous solutions. About 48 h was sufficient to attain maximum BTEX adsorption and desorption. Adsorption kinetics data proved a closer fit to the Weber–Morris model, while the isotherm experimental data were better fit to the Freundlich model, producing values of 1/n less than one, indicating favorable adsorption. Adsorption isotherms were determined in polluted surface water and it was found that the removal efficiency depends on the initial concentration of BTEX pollutants. Desorption equilibrium is less rapid than the adsorption equilibrium. BTEX adsorption/desorption was affected by chemical structure, solubility, and molecular weight. About 22% benzene, 33% toluene, 58% ethylbenzene, and 18.8% of p-xylene were released from RHAC after contact between the loaded matrix and reagent water. Sorption/desorption of p-xylene in RHAC was found to yield co-incident equilibrium isotherms and no significant hysteresis was observed.
The adsorption capacity of commercial powdered activated charcoal (PAC) was investigated for the removal of acyclovir from aqueous solutions. The effects of the initial acyclovir concentration (100-400 mg/L), pH (3-11), contact time, temperature (25-45 degrees C), and PAC dose (1-4 g/L) on the removal of acyclovir have been studied. The maximum removal was found to be 98% for 100 mg/L of acyclovir solution with 4 g/L of PAC dose at 45 degrees C. The results indicate that basic pH from 7 to 11 of acyclovir solution favored the adsorption on PAC. Moreover, the results showed that the adsorption kinetics can be represented by a pseudo-first-order model. The adsorption experimental data fitted in the order of decreasing accuracy as Freundlich, Redlich-Peterson, Temkin, Langmuir, and Dubinin-Radushkevich models. The Freundlich model was found the best to describe the equilibrium isotherm data of acyclovir adsorption on PAC. The maximum adsorption capacity of acyclovir determined from the Freundlich model was found to be 20.2 mg/g. The heat of adsorption was positive indicating endothermic nature and its low values (<70 kJ/mol) confirmed physisorption.
Batch adsorption of reactive blue H3R (B), red 3BF (R), and yellow FG (Y) dyes onto activated carbon (AC) and barley husk (BH) was studied. Various experiments were carried out to find the effect of initial dye concentration (5–100 mg/l), adsorbent dosage (0.1–1 g), contact time (15–420 min), pH solution (2.5–8.5), and temperature 30°C. The experimental data showed that the increasing uptake at decreasing pH with respect to (AC) was with B and R dyes while in comparison with (BH) was showed increased uptake at pH increasing for all dyes. Adsorption capacity increased with increasing initial concentration of all dyes with (AC) and (BH). The experimental data were analyzed using Langmuir, Freundlich, and Sips isotherm models. The adsorption of B, R, and Y dyes with (AC) was well fitted with all above models with R 2 (0.925–1), while adsorption onto (BH) for B dye showed R 2 (0.87–0.96) for above models, while for other dyes showed low R 2 values. Pseudo-first-order, pseudo-second-order kinetic, and intraparticle diffusion models were used to analyze the kinetic data. The data were well fitted at dye concentration 10 ppm with the pseudo-first order when R 2 values for B, R, and Y dyes were (0.88, 0.97, and 0.982) and (0.98, 0.947, and 943) for (AC) and (BH), respectively, while intraparticle models with R 2 values were (0.97, 0.9, and 0.818) and (0.932, 0.8, and 0.947) for each of (AC) and (BH), respectively. Pseudo-second-order model showed well fitting for (AC), when R 2 values were (0.77, 0.965, and 0.998) for B, R, and Y dyes, respectively.
The present work is concerned with a comparative study to evaluate the adsorptive properties of activated carbons produced from coffee grounds. Activation was done using different chemical activation agents such as H3PO4 and ZnCl2 either separately or mixed together. Characterization of these prepared samples was carried out by determining their physicochemical properties such as specific surface area, porosity, and surface acidity. The results indicated that the produced carbonaceous materials generally developed different and interesting porous structures. Indeed, H3PO4-activated carbon (PPAC-P) develops a porous volume of 0.98 cm3/g and a surface acidity of 317.6 meq/100 g (with a high mesoporous proportion). By contrast, ZnCl2-activated carbon (PPAC-Z) seems to be the most microporous material with a rather limited surface acidity. Adsorption trials with Malathion, a commercial pesticide widely used in Algeria, were carried out onto produced samples of carbonaceous materials in batch experiments at 30°C. Various parameters such as pH, contact time, nature, and amount of adsorbent were investigated for removal efficiency under different operational conditions. Results herein showed that an interesting removal efficiency of 96% was achieved under the following conditions: pH 6, adsorbent amount of 1 g/L, and an equilibrium time of 60 min.
The present work explored the use of Egyptian rice straw, an agricultural waste that leads to global warming problem through brown cloud, as a potential feedstock for the preparation of activated carbon. Chemical activation of this precursor using two different methods was adopted. The produced activated carbon was fully characterized considering its adsorption properties, as well as its chemical structure and morphology. Application of using the produced activated carbon and raw rice straw for removal of the Fe(III) was evaluated in a batch operation system. The results indicated that the rate of uptake of the Fe(III) is rapid in the beginning and 80% adsorption is completed within 50 min, and the time required for equilibrium adsorption is 60 min. The removal efficiency of Fe(III) depends on the pH of the solution. The optimal Fe(III) removal efficiency occurs at pH 5. The adsorption isotherm analysis showed that the Freundlish isotherm provides a good model for the sorption system. The 1/n is lower than 1.0, indicating that Fe(III) is favorably adsorbed by activated carbon.
Ozone (O3)/activated carbon (AC) coupling was studied for the removal of phthalates. These compounds, intensively used as additives (particularly as plasticizers), are suspected to be endocrine disrupters and carcinogenic compounds. The aim of this work was to study the removal of a mix of different phthalates (dimethylphthalate [DMP], diethylphthalate and diethylhexylphthalate) present in different matrices (deionised water, tap water, surface water and municipal wastewater treatment plant [WWTP] outflow) by O3/AC coupling. Two different ACs (basic and acid) were used to study the influence of the material on the coupling process. Results were compared to those obtained with both ozonation and adsorption processes. Degradation kinetics was modelled by a global pseudo-first-order kinetic model based on the sum of all the effects occurring during the treatment process. The results obtained with deionised water show that the degradation kinetics strongly depends on the pH value. Experiments performed with more complex matrices doped with phthalates show that the presence of natural radical scavengers and competitive reactions with other products lead to a significant decrease in the phthalate degradation kinetic constants, which vary for DMP from 0.262 min−1 (tap water) to 0.148 min−1 (municipal WWTP outflow). Nevertheless, in all experimental conditions, and with all the matrices used, O3/AC coupling was much more efficient at removing phthalates than conventional methods.
Adsorption of Cd(II) and Ni(II) ions on the modified activated carbon (WG-12) was measured. Two methods of activated carbon modification, i.e. a traditional method in a rotary furnace and a method developed by the author in a reactor that uses Joule’s heat, were analysed. The effects of performed modification were evaluated based on the surface area, water vapour adsorption, volume of micro-, meso- and macropores, and a number of oxygen groupings measured with the Boehm method. The application of these two methods resulted in the increase in adsorption of Ni2+ and Cd2+. The most favourable results for adsorption of both Ni2+ and Cd2+ were obtained for activated carbons modified in a rotary furnace at 800°C and with atmospheric oxygen at 400°C. Adsorption of Ni2+ and Cd2+ on activated carbons modified with Joule’s heat was slightly higher than in the case of activated carbons modified in a rotary furnace with carbon dioxide and water vapour at the same temperature (400°C). The presented method developed by the author is far more energy efficient. Less mass reduction and changes in a porous structure are observed which is favourable during adsorption of organic compounds.
The adsorption of detergents—sulfonic and phenolic compounds—from aqueous solutions by activated carbons (AC), obtained on the base of different precursors, was studied. The carbon adsorbents used were prepared by water vapor pyrolysis of different raw materials: peach stones, olive stones, natural asphaltite, mixtures from coal tar pitch, and furfural. It was established that all the samples of ACs have close values of high adsorption capacities toward the studied detergents. Some factors affecting the adsorption process—the time of treatment and the amount of the adsorbent—were investigated. It was established that the amount of adsorbent has no significant influence on the adsorption process.
Several studies, both theoretical and experimental, have already proven that mathematical modelling of wastewater treatment plants (WWTP) is an elegant and cost-effective tool to study and to optimise these treatment processes. In most cases, interpretation of the simulation results is done on ad hoc complex databases based on so-called expert knowledge. As such, the interpretation of the results becomes difficult. In this study, interpretation of the WWTP simulation results is aided by the means of principal component analysis (PCA). The main influencing factors were found to be the influent flow rate and load, and the settler performance in terms of the non-settleable fraction of the biomass. A PCA analysis indicated three principal components. The first principal component explained 37% of the total variance and contains most of the information on nitrogen removal. The second principal component (PC2) explains 20% of the total variance and can be considered as a measure of the secondary settler performance. The third principal component (PC3) explains 17% of the total variance and mostly contains information on the different flow rates in the WWTP (influent flow rate, nitrate recycle flow rate, sludge recycle flow rate and waste flow rate).
A separation for Cd2+ and its interferences of common cations (Na+, NH+, K+, Mg2+, and Ca2+) was performed. Cation-exchange ion chromatography for Cd2+ and common cations separation on a weakly acidic H+ forming cation-exchange resin was investigated and applied to test the efficacy of activated carbon in the removal of Cd2+ from simulated wastewater. The difference of retention volumes between Ca2+ and Cd2+ was 0.45 mL for oxalic acid with a concentration of 1.75 mM, and the retention volume drastically decreased when the oxalic acid concentration increased in the eluent. Considering the prevailing conditions for TOSOH TSK gel Super IC A/C at 40°C with a least pH limit of 2.0, 1.75 mM of oxalic acid was selected for rapid analysis with pH of 2.3. Applying 50 μL sample injection, the calibration curve was linear for tested standard samples ranging from 0.05 to 2.0 mg/L, the detection limit (S/N = 3) was 0.066 mg/L (0.583 μM), and the analysis was applicable with coexisting Ca2+ up to 10.0 mg/L (250 μM) while other cations did not interfere. It was possible to analyze three samples within an hour. The application of this method on Cd2+ adsorption indicated the effectiveness of the method for heavy metals’ analysis.
The aim of this paper is to study the treatment of 4-chlorophenol bearing water by biological treatment in sequencing batch reactor (SBR) without any adsorbent (blank-SBR) and with an SBR loaded with granular activated carbon (GAC–SBR) in instantaneous mode. Adsorbent dose used for GAC–SBR was found to be 16 g/L. It was observed that addition of GAC enhanced the ability of activated sludge in resisting the shock load of organics. React phase duration in blank-SBR and GAC–SBR was found to be 6 and 4 h, respectively. Removal efficiencies of blank-SBR and GAC–SBR at optimum conditions and for initial 4-chlorophenol concentrations of 100, 200, 250, and 500 mg/L were found to be 68.6 and 97%; 46.9 and 96.9%; 23.5 and 96%; and 5 and 95.9%, respectively. Kinetics of treatment process has been studied in both blank-SBR and GAC–SBR. Characterization of the sludge was done using scanning electron microscopy (SEM)/energy dispersive atomic X-ray (EDAX) analysis. Settling and filterability characteristics of the sludge have also been studied.
In this study, the reduction chemical oxygen demand (COD) in water-based paint wastewater using commercial activated carbon, activated date pits and rice husks was investigated. The process was studied in the batch mode with respect to the initial pH, contact time, and adsorbent dose. Adsorption equilibrium and kinetic data were determined for the three adsorbents and were fitted to several isotherm and kinetic models accordingly. The results indicated that activated rice husks (ARH) and activated date pits (ADP) were as effective as commercial activated charcoal (CAC) in the reduction of the effluent COD reaching a maximum of 83% using 180 g/L ARH and 76% using 120 g/L ADP. Kinetically, the results showed that reduction of COD onto both ADP and ARH was better fitted to pseudo-second-order model which involved particle/pore diffusion. In addition, equilibrium adsorption data for the reduction of COD effluent ADP and ARH was best represented by the Langmuir model.
Precursor was prepared from rice husk under different carbonization temperatures. Then, activated carbon (AC) was synthesized by NaOH activation. The specific surface area of carbon increased with temperature rise up to 600°C, but decreased rapidly over 600°C. So, the AC obtained at 600°C possessed the outstanding surface area of 2,802 m2/g. And, its adsorption activity of nitrate was carried out at initial concentration of 50–400 mg/L. The results showed that the maximum adsorption capacity and removal percentage of [Inline formula] were 70.2 mg/g and 70.6%, respectively. Besides, the experimental data were evaluated by Langmuir, Freundlich, and Redlich–Peterson isotherms. In kinetic studies, it was observed that the results were well explained by the pseudo second-order model. In addition, the Gibbs free energy change of −17.0 kJ/mol indicated that the adsorption process was spontaneous.
Minimization of excess sludge production may be achieved by either changes in operational conditions or by the treatment of recycled activated sludge. It was investigated using ozone-treated return activated sludge in lab-scale activated sludge process operated continuously with optimum conditions determined using Box–Behnken experimental design method as 400 mg/L initial chemical oxygen demand concentration (CODi), 25 h hydraulic retention time, and 25 d solid retention time, respectively. Batch experiments were carried out in order to determine the optimum ozone dose of 0.05 g O3/g total solid considering disintegration degree (DD). Ozone reactor (OR) and control reactor (CR) were evaluated considering sludge reduction capacity, effluent quality, and sludge characteristics. About 61 and 40% reductions can be achieved in mixed liquor suspended solid concentration and observed sludge yield value in OR compared to CR, respectively. The effluent quality in terms of COD and NH4–N removal in OR was not significantly affected by ozonation. The dewatering capacity was slightly weakened while little improvement was observed in filtering capacity in OR compared to CR, in terms of capillary suction time and specific resistance to filtration. Particle size changed and sludge destruction led to an increase of small particles.
Reactive yellow dye was investigated as an adsorbate to be removed onto activated carbon during batch and continuous processes. A Fourier transform infrared (FTIR) analysis was carried out before and after onto the activated carbon adsorption. Thermodynamic parameters: Gibbs free energy, enthalpy change, and entropy change were found at different temperatures. Isotherm experiments were carried out at different conditions: adsorbent dosage (0.1–0.5 g), temperature (20–50°C), pH (2.5–9), and initial concentration (50–150 mg/l). Langmuir, Freundlich, and (Brunauer, Emmet, and Teller) BET isotherm model were used to fit the results. Kinetics mechanism of mass transfer pseudo-first-order, pseudo-second-order, and intraparticale diffusion models were studied. Fixed bed column experiments were carried out at different bed heights (0.05–0.15 m), initial concentration (10–50 mg/l), and flow rate (4–12) 10−6 m3/min to find empty bed contact time at break though point. Bed depth service time model was used as a shortcut model to predicate the breakthrough curves comparing with experimental data.
This study reports tannic acid adsorption onto commercial activated carbon (ACC) in a batch system. Adsorption process parameters namely pH, adsorbent dose (m ad), temperature (T), initial tannic acid concentration (C o), and contact time (T) were studied and optimized. Optimum pH and adsorbent dose were found to be 3.0 and 15 g/l, respectively. Equilibrium contact time was found to be 7 h. Pseudo-second-order kinetic best fits the adsorption kinetic data. Three isotherms namely Langmuir, Temkin, and Redlich and Peterson (R–P) isotherms were studied and it was found that Langmuir and R–P isotherm generally fitted the experimental equilibrium adsorption data. Endothermic nature of the adsorption of tannic acid onto ACC was concluded, and heat of adsorption was found to be as 89.55 kJ/mol. On considering the cost of ACC, regeneration studies of Tannic acid (TA) loaded ACC have been performed using solvent and thermal desorption methods.
Linear alkylbenzene sulfonates (LASs) are anionic surfactants with extensive application as detergents. Discharge of wastewater containing these chemicals results in negative environmental impacts. In the present study, the process performance of an extended aeration activated sludge (EAAS) system in Paveh’s wastewater treatment plant (WWTP) and a conventional activated sludge (CAS) system in Kermanshah’s WWTP removing LAS and chemical oxygen demand (COD) were compared. The amounts of LAS removal in the CAS and the EAAS systems were calculated as 93.73 and 96.7%, respectively. It was concluded that EAAS system may be used for treating municipal wastewater with better LAS, COD, and total suspended solids (TSS) removal efficiency compared with CAS system.