Liquid Phase Adsorption of Phenol and Chloroform by Activated Charcoal

The adsorption equilibria of phenol and chloroform from aqueous solutions on four different particle sizes of activated charcoal were examined at different initial concentrations of the adsorbates. The experimental data were analyzed using the Langmuir and Freundlich isotherm models. Both models fit the adsorption data for phenol. The Freundlich model more accurately fits the adsorption data for chloroform than the Langmuir model. The sorption kinetics for phenol was studied using pseudo‐first‐order and second‐order kinetic models. The adsorption data better fit the second‐order model. The results of the study show that activated charcoal can be used as potential adsorbent for phenol and chloroform in drinking water.     

Kinetic Description of Industrial Wastewater Ozonation Processes

Literary and experimental data on the ozonation kinetics of aqueous solutions and wastewater were analyzed. COD was suggested to be used as a kinetic parameter from the solution side. On the basis of the results obtained from the ozonation of model solutions and wastewater, the rate coefficient by COD of the reaction was shown to be constant during separate stages of the process. Due to the consumption of fast-reacting components and entering into the reaction of more slowly reacting intermediate products, the rate coefficient changed spasmodically with transition from one stage to another. The reaction order with respect to the COD of the solution was shown to be equal to the reaction order with respect to the pure component.     

Adsorption Properties of Activated Tire Pyrolysis Chars for Phenol and Chlorophenols

The adsorption of phenol (Ph), 4-chlorophenol (4CP), and 2,4-dichlorophenol (DCP) from aqueous solutions on activated tire pyrolysis chars (ATPCs) was studied in a batch system, including both kinetics and equilibrium. Different kinetic models and adsorption isotherms were used to describe the adsorption behavior of the phenols. The kinetic study shows that the process can be described by a pseudo-second-order model. The best fitting results for the equilibrium adsorption data were obtained with the Sips isotherm. Adsorption of the selected phenols on all of the adsorbents increased in the order Ph < 4CP < DCP. The effect of ionic strength and pH on the adsorption was also studied. The results show that the ATPCs could be used as adsorbents for the removal of phenols from aqueous solutions.     

Iron and Manganese Removal with Ozonation in the Presence of Humic Substances

The conditions for the removal of iron and manganese contained in slightly mineralized water, rich in humic substances, were determined in a case where an intermediate oxidation was provided in a conventional potabilization line comprising a coagulationflocculation stage with iron salts.

The experiments were conducted both on a synthetic water, with or without addition of humic substances, and on raw water from the Moulin-Papon dam. While iron was easily removed by simply increasing the pH measurement from 8.2 to 8.5 without intermediate oxidation, ozonation applied to water with a pH of nearly 8.4 did not enable the manganese to be removed with a low ozone dose (about 1 mg/L) unless a significant amount of bicarbonates (120 to 130 mg/L as CaCO₃) were injected prior to the ozonation-filtration stage.

As it removes the manganese from the water, intermediate ozonation also removes the abatement of organics on the filters, and lowers the THM buildup potential.     

Ozonation of Non-Biodegradable Mixtures of Phenol and Naphthalene Derivatives in Tanning Wastewaters

The decomposition of non-biodegradable mixtures of phenol and naphthalene derivatives in aqueous solution by ozonation is investigated. The toxic water pollutants are the intermediate synthesis products obtained via the sulfonation reaction of naphthalene and phenol. These organic compounds are phenol (PH), p-phenol sulfonic acid (p-PSA), and 2-naphthalene sulfonic acid (2-NSA). The kinetic study of ozonation is realized by the pH variation in the range of 2–12. The pH-dependence of the ozone reactivity for different organics is observed. The intermediates and final products determination is measured by UV absorbency and HPLC technique. It is shown that the main sub-products are muconic, fumaric, maleic and malonic acids and catechol. The final products are basically oxalic acid and formic acids as well as formaldehyde. In the initial stage of ozonation, hydroxylation and desulfuration of p-PSA and 2-NSA is detected. The effect of the preliminary ozonation on the biodegradability of the contaminants is estimated by BOD₅/COD-ratio variation, which significantly increases from 0.15 to 0.88.     

Comparison between Ozonation and Photo-Fenton Processes for Pesticide Methomyl Removal in Advanced Greenhouses

So-called “Advanced Greenhouses” are a new approach to the concept of protected agriculture. Among other technological and structural improvements, these facilities give the possibility of recycling the irrigation surplus water, rich in lixiviates, salts, pesticides and its metabolites. After many cycles, the current is so concentrated on those substances that it becomes necessary for the presence of a membrane separation stage which brine, highly concentrated on those named pollutants, has to be treated before being sent to the public sewage system. Advanced Oxidation Processes, among other chemical treatments, can be considered an alternative to process this current effluent. In this work, concentrated aqueous solutions of methomyl as model pesticide (200 mg·L^?1) have been subjected to two of those processes: ozonation and photo-Fenton reaction. Analysis of the elimination of the pesticide itself and the grade of mineralization achieved have shown how, while the ozonation is the most effective process decomposing the pesticide (eliminating the total concentration in 60 minutes), the photo-Fenton reaction mineralizes successfully the 40% of the total organic load (the ozonation only can cope with 20%) but only decompose a 40% of the pesticide. Evolution of biodegradability and toxicity of the effluent along both processes was also analyzed. Intermediates generated both by ozonation and photo-Fenton did not increase the biodegradability of the treated effluents. Nevertheless, while acute toxicity just after 15 minutes of treatment with ozone is notably higher than for raw solution, and it is maintained till the end of the experiment (120 min), though, toxicity along photo-Fenton reaction has two growing and decreasing regions, always shows lower values than the provoked during ozonation. None of the two assayed processes has been proved to increase biocompatibility of highly concentrated methomyl solutions.     

Removal of Pesticides by a Combined Ozonation/Attached Biomass Process Sequence

Different combinations of ozonation and biological treatments were tested on an industrial effluent containing high pesticide concentrations. Ozonation was performed in 450 L columns at 1.5 h HRT each. Biological treatment was carried out in a submerged filter (BIOFOR). Ozone was effective in removing herbicides but dosages up to 1000 mg L^?1 were needed. The improved biodegradability of the organic compounds after pre-ozonation was demonstrated by Oxygen Uptake Rates (OUR) tests and by the efficiency of biological treatment towards COD, and pesticides. The Italian discharge limit of 50 ppb total pesticides was achieved by combining pre-ozonation, biological treatment, and post- ozonation.     

活性炭吸附法脱除废水中的苯酚及吸附剂再生的研究

对活性炭对废水中苯酚的吸附平衡以及活性炭的再生进行了试验性研究和理论性探讨。结果发现,温度对活性炭的吸附能力有显著的影响,低温地吸附有利,吸附平衡可用Ｌａｒｇｍｕｉｒ方程描述;ＰＨ值对活性炭对苯酚捐附也有较强的影响,酸性的水溶液对吸附有利,强碱性水溶液对再生有利。分别采用乙醇、丙酮、ＮａＯＨ溶液、ＮａＯＨ溶液＋乙醇的混合液对吸附剂活性炭进行再生,再生率均能达到８５％以上,基本满足工业要求。     

Removal of a Toxic Anthraquinone Dye by Combination of Red Mud Coagulation and Ozonation

Removal of a toxic anthraquinone dye—Disperse Blue 56 (DB56) by single red mud (RM) coagulation, single ozonation and combined RM coagulation/ozonation (RM/O₃) was carried out in laboratory-scale experiments. RM/O₃ treatment exhibited more effective in toxicity removal, color removal and chemical oxygen demand (COD) reduction than the other two methods. The effect of several operational parameters, including initial dye concentration, pH value, RM coagulant dose and O₃ dose, on color removal and COD reduction was also investigated. Among these factors, pH value had the most important effect.     

Modelisation Of Micropollutant Removal In Drinking Water Treatment By Ozonation Or Advanced Oxidation Processes (O3/H2O2)

A simulation program is described, tested and used, to predict micropollutant removal in an ozonation bubble tower with or without hydrogen peroxide addition. To compute the removal efficiency, we need to know the chemical reactivity between organic compounds and oxidant species (molecular ozone and hydroxyl radicals), the ozone mass transfer from the gaseous phase to the liquid phase (k_La) and the hydrodynamic model describing the reactor. In this case, we divide the reactor into three parts (water arrival, air arrival and intermediate zones). Each part is modelled using completely stirred tank reactors in series (CSTR).

In each CSTR, the calculation of oxidant concentrations (O₃, H₂O₂) is made through mass balance equations and a semi-empirical formula which gives hydroxyl radical concentrations as a function both of ozone concentration and the main characteristics of the water to be treated (pH, TOC, alkalinity). Another semi-empirical formula links ozone consumption to the same characteristics.     

Investigation into Ozonation of Coal Coking Processing Wastewater for Cyanide,Thiocyanate and Organic Removal

A laboratory investigation was carried out to establish whether ozonation could be used to oxidize cyanides, thiocyanates and color in wastewater from a coal coking plant to supplement biological and activated carbon treatment (GAC). Ozonation was found to be capable of oxidizing cyanide and cyanate to sufficiently low levels at relatively high stoichiometric ratios as a result of competitive ozone consumption by organic substances in the wastewater. While good color removal was also achieved with ozonation, organic removal could not match GAC in overall organic removal. Ozonation was not found to be economical for the remaining nine years of a build, own, operate and transfer (BOOT) contract period. Ozonation would be competitive over longer operational periods and more environmentally friendly than presently used technology.     

Removal of iron from drinking water by electrocoagulation: Adsorption and kinetics studies

The present study provides an electrocoagulation process for the removal of iron from drinking water with aluminum alloy as the anode and stainless steel as the cathode. The studies were carried out as a function of pH, temperature and current density. The adsorption capacity was evaluated with both the Langmuir and the Freundlich isotherm models. The results showed that the maximum removal efficiency of 98.8% was achieved at a current density of 0.06 A dm⁻², at a pH of 6.5. The adsorption of iron preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. The adsorption process follows second-order kinetics. Temperature studies showed that adsorption was endothermic and spontaneous in nature.     

Abatement of 4-Chlorophenol in Aqueous Phase by Ozonation Coupled with a Sequencing Batch Biofilm Reactor (SBBR)

The aim of this work was to assess the mineralization of 100 and 200 mg L^?1 4-chlorophenol (4-CP) solutions by ozonation-biological treatment. The results show that starting from a 4-CP initial concentration from 100 to 500 mg L^?1 and using an ozone flow rate of 5.44 and 7.57 g h^?1, 4-CP was completely removed. A kinetic constant around 9·10^?2 min^?1 was calculated for the ozone direct attack. The biodegradability (BOD₅/COD) of the pre-ozonated solutions increased from 0 until a range between 0.2–0.37. The combination of the ozonation and aerobic biological treatment in an aerobic sequencing batch biofilm reactor (SBBR) gave an abatement of more than 90% of the initial TOC.     

Effect of Catalytic Ozonation Coupling with Activated Carbon Adsorption on Organic Compounds Removal Treating RO Concentrate from Coal Gasification Wastewater

This paper reports a novel system of catalytic ozonation coupling with activated carbon adsorption for removing the organic compounds treating in the RO concentrate from coal gasification wastewater. The effect of ozone dosage, catalyst dosage, reaction time, influence pH, and temperature on organic compounds removal were examined for the processes. In the catalytic ozonation process, increasing solution pH, dosages ozone, and catalyst were statistically significant for improving the performance. In addition, the high salinity with chloride concentration of 15 g/L could reduce the catalyst specific surface area by 18%. Thus, high salinity showed negative influence on the catalytic effect in TOC removal. Regarding activated carbon adsorption process, modified activated carbon by NaOH revealed advantages in adsorbing organic compounds treating catalytic ozonation effluent. With the ozone dosage of 120 mg/L, catalyst dosage of 2.0 g/L, catalytic ozonation reaction time of 1 h, and modified activated carbon adsorption time of 1 h, the average TOC removal efficiencies were maintained at the stable level of 58% with the TOC concentration of 26 mg/L.     

Systematic Approach to Quantify Adsorption and Biodegradation Capacities on Biological Activated Carbon Following Ozonation

The goal of this research was to develop a systematic approach to quantify adsorption and biodegradation capacities on biological activated carbon (BAC). The role of absorption and biodegradation on BAC was studied using a continuous column. Several media, i.e., granular activated carbon (GAC), seeded glass bead and seeded GAC, and a target compound (p-hydroxybenzoic acid) were selected. Before breakthrough, the effluent of the GAC column contained a small amount of p-hydroxybenzoic acid that contributed the greatest amount of organic carbon to the effluent of the glass bead column, which suggests that adsorption should be the prevailing mechanism for removal the p-hydroxybenzoic acid, and biodegradation should be responsible for reducing the ozonation intermediates. Also, the bioactivity approach (biomass respiration potential, BRP) of BAC can not only reveal the importance of biodegradation mechanisms for the intermediates of ozonation, but also quantify the extent of the adsorption or biodegradation reaction occurring on BAC.     

Phenol Removal from Aqueous Solutions by Tamarind Nutshell Activated Carbon: Batch and Column Studies

Activated carbons prepared from tamarind nutshell, an agricultural waste by‐product, have been examined for the removal of phenol from aqueous solutions. The activated carbon was prepared by sulfuric acid activation. Both batch and column studies were performed for the sorption of phenol. The kinetic data were fitted to the models of Lagergren, pseudo‐second‐order and intraparticle diffusion, and closely followed the pseudo‐second‐order chemisorption model. The Freundlich and Langmuir isotherm models were well fitted. The solution pH greatly affects the sorption process. The column study results indicate that the sorption of phenol is dependent on the flow rate, the inlet phenol concentration as well as on the particle size of the adsorbent.     

Combination of Ozonation and the Fenton Processes for Landfill Leachate Treatment: Evaluation of Treatment Efficiency

Single processes such as ozonation, ozone/hydrogen peroxide, Fenton and several combined treatment schemes were applied for leachate collected from a waste disposal site. The implementation of combined Fenton and ozonation processes resulted in the highest chemical oxygen demand removal (77% from initial value) among all the treatment methods applied, while biodegradability improvement was observed during the Fenton pre-treatment only. Some decrease of chemical oxygen demand was obtained during the single ozonation or combined schemes including ozone resulting in slight if any biodegradability improvement. The addition of hydrogen peroxide to ozonation did not enhance chemical oxygen demand, dissolved organic carbon or biochemical oxygen demand removal compared to ozone alone. Ferric chloride coagulation used as a pre-treatment stage did not improve subsequent chemical oxygen demand removal by ozonation or the Fenton processes. Taking into account the effective chemical oxygen demand, dissolved organic carbon removal and biodegradability improvement the single Fenton process seems to be a preferable treatment method for the leachate treatment. Some reduction in toxicity to Daphnia magna was observed after the application of the studied treatment methods.     

Adsorption of Phenol from Aqueous Systems onto Spent Oil Shale

Abstract

To evaluate its ability to remove phenol from aqueous solution, Jordanian “spent” oil shale, an abundant natural resource, has been used in an experimental adsorption study. Equilibrium of the system has been determined at three temperatures: 30, 40, and 55C. The resulting experimental equilibrium isotherms are well represented by Frendlich, Langmuir, and Redlich-Peterson isotherms. The relevant parameters for these isotherms, as regressed from the experimental equilibrium data, are presented. Effects of solution pH (in the range of 3–11), in addition to effects of three inorganic salts (KI, KCl, and NaCl, each at 0.1, 0.01, and 0.005 M), on the equilibrium isotherms have been experimentally investigated. The effects of pH in the presence of KI and NaCl were also investigated for a possible interaction between salts and solution pH. The initial concentration of phenol in the aqueous system studied ranges from 10 to 200 ppm. Experimental results show that while an acidic solution has no effect on the adsorption capacity of spent oil shale to phenol, a highly basic solution reduces its adsorbability. No sound effect was observed for the inorganic salts studied on the adsorption of phenol on spent oil shale. The experimental results show that there is no interaction between the pH of solution and the presence of salts. In spite of its ability to remove phenol, spent oil shale showed a very low equilibrium capacity (of an order of magnitude of 1 mg/g). Should the adsorption capacity of the shale be improved (by different treatment processes, such as grafting, surface conditioning), results of this study will find a direct practical implication in serving as “raw” reference data for comparison purposes. salts. The experimental results show that there is a certain degree of coupling between the pH of a solution and the presence of KI salt. Other salts have shown no interaction with the solution pH. The experimental results are explained in terms of the degree of ionization of the adsorbate which is controlled by the pH of the solution.     

Mathematical Modeling of Theoretical Cryptosporidium Inactivation in Full-Scale Ozonation Reactors

Conditions for theoretical inactivation of Cryptosporidium by ozone could be achieved at full-scale facilities if their design is appropriate. To perform this task correctly the chemical engineer's approach for process design must be applied. This paper discusses the basic equations the estimation of the disinfection efficiency of different ozone reacting systems. Available kinetic data have been integrated in a global model accounting for the hydrodynamics and mass transfer performances of the ozonation reactor. Thus the proposed method allows one to predict Cryptosporidium inactivation level in a given ozonation system. However, if a specified disinfection goal is to be achieved for Cryptosporidium with the developed model it is also possible to choose and optimize the design of the ozone reactor.     

Ozonation Dynamics and Its Implication for Off-Gas Ozone Control in Treating Pulp Mill Wastewaters

Ozonation of biologically pretreated pulp mill wastewaters was studied using both bench and pilot scale fine bubble contactors to determine the oxidation efficiencies, mass transfer coefficients (k_La) and enhancement factors (E) due to the occurrence of chemical reactions. A sensitivity analysis based on the measured process parameters was then used to reveal the interrelated effects of key factors on off-gas ozone concentrations. It was shown that the removal efficiencies of color and AOX were simply related to the amount of utilized ozone, regardless of variation of other operating conditions. Furthermore, the rate of absorption fell within the fast or instantaneous kinetics regimes due to the occurrence of rapid chemical reactions. The Ek_La values were found to vary substantially during the course of ozonation, indicating that the enhancement factors were not only affected not only by operating conditions but also by wastewater characteristics. To effectively control the off-gas ozone emission, measures should be taken to minimize the backmixing, use a counter-current flow arrangement and provide adequate contact time.