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In recent years, people’s environmental awareness has increased. The high density of the urban population has caused a considerable increase in the demand for car washing services, which has created large quantities of car wash wastewater. The main pollutants in car wash wastewater are detergents, dirt, oil, and grease. Untreated wastewater released into rainwater sewer systems or other water bodies may pollute the water and generate excessive bubble foams, which negatively affects urban appearance. Car washes are divided into mechanical car washes and manual or self-service car washes. In general, car washes have a small operation and scale, occupy limited land, and cannot afford wastewater treatment costs. Therefore, most car washes are not equipped with wastewater treatment facilities. Consequently, the discharge of wastewater from car washes negatively affects the water quality in the surrounding environment and results in wasteful use of water resources. This study reviewed 68 research papers on the quality, treatment techniques, treatment costs, and treatment effectiveness of car wash wastewater to provide a reference for car wash operators to contribute to the preservation of water resources. We found that there is a higher chance of recycling car wash wastewater when combing two different techniques for car wash wastewater treatment.

Considering the lack of information on simultaneously removing multiple pharmaceuticals from water or wastewater by electrochemical methods, this study aimed to investigate the removal of multiple pharmaceuticals by electro-coagulation and electro-oxidation based on two types of electrodes (aluminum and graphite). The synthetic wastewater contained a nonsteroidal anti-inflammatory drug (diclofenac), a sulfonamide antibiotic (sulfamethoxazole) and a &beta, blocker (atenolol). The pharmaceutical removal with electro-oxidation was much higher than those with the electro-coagulation process, which was obtained from a five-cell graphite electrode system, while the removal of pharmaceuticals with aluminum electrodes was about 20% (20 &micro, M). In the electro-coagulation system, pharmaceutical removal was mainly influenced by the solubility or hydrophilicity of the compound. In the electro-oxidation system, the removal mechanism was influenced by the dissociation status of the compounds, which are attracted to the anode due to electrostatic forces and have a higher mass transformation rate with the electro-oxidation process. Therefore, atenolol, which was undissociated, cannot adequately be eliminated by electro-oxidation, unless the electrode&rsquo, s surface is large enough to increase the mass diffusion rate.

Perfluorooctanoic acid (PFOA) was separated and recovered using a foam flotation process aided by cationic surfactants. The PFOA removal efficiency was in the following decreasing order: OTAB (C8TAB) > DTAB (C10TAB) > CTAB (C16TAB) > TBAB, which indicates that cationic surfactants with an alkyl chain that had a similar length to that of PFOA had higher affinities to PFOA. PFOA removal slightly decreased with increasing ionic strength of the surfactant but did not change with the pH. PFOA could be completely removed in 20 min with 1.25 mM of OTAB in actual wastewater. The energy yield value of foam flotation with a cationic surfactant was much higher than those of other methods, which means that using foam flotation with a cationic surfactant as the collector is a simple, fast, and energy-efficient method to separate and recover PFOA from dilute water solutions.

In this study, we evaluated the feasibility of treating water contaminated with ketoprofen (KET) by ultrasound (US) and sono-activated persulfate (US/PS) systems. The effects of different reaction parameters, such as the initial pharmaceutical compound concentration (C0), persulfate concentration, ultrasonic power, and initial pH of the solution (pHi) on the KET removal and reaction kinetics were investigated. Tert-butyl alcohol (TBA) was used as a chemical probe to identify the predominant radicals in the US and US/PS systems. The results demonstrated that the persulfate oxidant can be activated by US under neutral and alkaline conditions. Moreover, KET was predominantly degraded by hydroxyl radicals (HO.) generated by the activation of persulfate. Under alkaline conditions, the removal efficiency of KET improved with increasing amount of persulfate added. HO. was the dominant radical at a more alkaline pH in both US and US/PS systems, which was verified by the tert-butyl alcohol probe. These results provide insights into the treatment of water contaminated with pharmaceutical compounds.

In this study, the electrocoagulation (EC) of perfluorooctanoic acid (PFOA) by an aluminum electrode with the addition of zinc salt was investigated. Adding ZnCl2 successfully prevented a rise in pH during EC and increased the efficiency from 73.7% to over 99%. In addition, the longer the carbon chain of a PFA was, the better the removal of that PFA by electrocoagulation. The main functions of ZnCl2 were to prevent the rise in pH and improve flotation because the flocs with added ZnCl2 were easy to gather together and had a faster floating speed. The XPS results demonstrated the occurrence of bonding between aluminum and fluoride. This finding indicates that complexation between aluminum and fluoride may be the main mechanism for removal when aluminum electrodes are used to remove perfluoroalkyl (PFA) compounds.

Thermally-activated persulfate (PS) has been recognized as one of the most effective Advanced oxidation processes (AOPs) to oxidize Persistent perfluorooctanoic acid (PFOA). Applications of Carbon aerogel (CA)-activated PS for PFOA decomposition at 25, 40, 50 and 60 °C were evaluated. With the presence of CA in PS oxidation, 85.7% of PFOA was decomposed to fluoride ions and intermediates of short-chain perfluorinated carboxylic acids (PFCAs) with a 34.5% defluorination efficiency at 60 °C after 8 h. PFOA was decomposed and mineralized to fluoride ions in the CA + PS system following a stepwise degradation process of C6F13COOH → C5F11COOH → C4F9COOH → C3F7COOH → C2F5COOH → CF3COOH at 60 °C. The decomposition and defluorination rates of the combined CA + PS system at 60 °C were approximately 1.83 and 1.61 times faster than those of the PS-only system, respectively. With CA in the PS system, activation energies of PFOA removal and defluorination were significantly reduced from 66.8 to 37.2 and 97.3 to 49.2 kJ/mol, respectively. It implies that applying CA could effectively promote the PFOA degradation that leads to significant savings in energy consumption and reductions in process time. Characteristics of CA used were evaluated by using N2 adsorption, zeta potential, Raman, SEM, XRD, XPS and FT-IR techniques. A quenching test was conducted by using methanol as an inhibitor and Electron spin resonance (ESR) spectra of free radicals were analyzed for development of proposed reaction mechanisms.

Children may be exposed to environmental contaminants through incidental ingestion of soil resulting from hand-to-mouth contact. We measured soil adherence to the skin among 86 children from four kindergartens and one elementary school in Taiwan. Rinse water samples were collected from the hands, forearms, feet and lower legs of children after they had engaged in assigned activity groups (pre-activity, indirect contact and direct contact) from two different soil textures groups: sand and clay. We found that the soil loadings significantly differed between the different soil textures, body parts, activities, and clothing groups. Measured soil loadings for hands of pre-activity, indirect contact activity, and direct contact activity groups were 0.0069, 0.0307 and 0.153 mg cm−2, respectively, for the group playing on sand and 0.0061, 0.0116 and 0.0942 mg cm−2, respectively, for the group playing on clay. To facilitate the use of soil adherence data in exposure assessments, we provided a new and simple way to group activities based on the intensity of children's interactions with soil. The adherence data from this study can help enhance existing information based on soil-to-skin adherence factors used to assess children's exposure to soil contaminants during their play activities.

In this study, the effects of integrating chloride addition and ultrasonication with electrocoagulation (EC) to remove passive layers were investigated. Experimental results were evaluated by conducting an impedance modulus analysis and by considering the amounts of aluminum released. The effect of different operating parameters, such as the phosphate concentration, ultrasonic power, chloride concentration, and the number of cycles on the efficiency of phosphate removal was examined. The results indicated that the integrated ultrasonic and chloride addition process effectively enhanced the energy efficiency and lifespan of plates due to the reduction of the electric impedance. The concentration of released aluminum increased from 150 to 440 mg/L with the increase of ultrasound from 0 to 100 W. After three test cycles, the use of the ultrasonic process and chloride addition with EC enhanced the phosphate removal efficiency. The removal efficiency of the EC process decreased to 30%; however, the removal efficiency of the integrated process increased to 90%. Scanning electron microscope images showed that using ultrasound could successfully remove the passivation layer on the electrode to enhance the phosphate removal efficiency. However, excessive ultrasonic intensity would result in a thicker passivation layer and thus decrease the removal efficiency. It suggests that the coupled use of chloride addition and ultrasonication in the EC process effectively reduced the passivation layer, thereby increasing the energy efficiency while decreasing the impedance modulus and enhancing the concentration of aluminum ions.

The degradation of pharmaceuticals by electrochemical oxidation (EO) in simulated wastewater containing multiple pharmaceuticals was compared between batch and continuous reactors. Despite the excellent efficiencies achieved in batch experiments, the practical/large-scale applications of EO-degrading amine-containing pharmaceuticals has not yet been accomplished. This paper presents the results of continuous experiments with one of the most promising electrochemical configurations of Pt/Ti electrodes before proceeding to application. In the continuous electrooxidation system (without chloride), direct oxidation on the electrode surface and oxidation by hydroxyl radicals were the main pathways. Due to their short lifespans, the radicals could not be transferred to the bulk solution, and the removal of pharmaceuticals followed the order of sulfamethoxazole (SMX) > paracetamol (PAR) > diclofenac (DIC). In the electrochlorination system (with chloride), oxidation by residual chlorine was the main pathway. The removal of pharmaceuticals followed the order of sulfamethoxazole (SMX) > diclofenac (DIC) > paracetamol (PAR). High SMX removal was realized because of the high reaction rate of SMX with free chlorine. Among the pharmaceuticals, PAR had the lowest removal because it is a neutral species with a low mass transfer rate without the attraction of electrostatic force. These results are consistent with the predictions from our previous batch-scale study, which showed that the reaction rate of dissociated compounds could be increased by the addition of electrostatic force. Furthermore, multiple coexisting pharmaceuticals, such as SMX and PAR or DIC, may form dimers that can be transferred to complex structures and cause higher toxicity.

Acetaminophen is commonly found in aquatic environments because it is widely used as an analgesic. In this study, the extent of transformation and adsorption of acetaminophen by manganese dioxide (MnO2) at different pH conditions was systematically investigated. The adsorption of acetaminophen by MnO2 was significant under acidic conditions but negligible under neutral and alkaline conditions. This indicates that the rate-determining steps in the removal of acetaminophen are electron transfer under acidic conditions and precursor complex formation under neutral and alkaline conditions. The kinetic simulation result is consistent with the above results, and the kinetics can be described using a surface complexation and transformation kinetic model if the initial concentration of acetaminophen exceeds the total concentration of the reactive surface sites on MnO2. Otherwise, the Michaelis–Menten model and the pseudo-first-order kinetic model can be used to describe the removal kinetics under acidic conditions and under neutral and alkaline conditions, respectively. The main transformation products were p-benzoquinone and a dimer of 4-aminophenol and acetaminophen under acidic and alkaline conditions, respectively. This indicates that dehydration–oxidation is the main pathway only under acidic conditions. Under alkaline conditions, the main transformation mechanism is dimerization–hydrolysis.

In this study, ultrasonic treatment was used to remove the passive film that formed on electrode surface during electrocoagulation (EC). The variation of electrode impendence was examined to evaluate the effect of passivation on EC and the ultrasound-electrocoagulation (sono-EC) process. The effects of operating parameters current density, pH and ultrasonic power on the removing efficiency in sono-EC were studied. A synthetic wastewater that contained Reactive Blue 19 dye was used in all experiments. The results demonstrated that the electrode impedance increased during the EC process but decreased during the sono-EC process, indicating that the passive film can be removed from the sacrificial electrode using ultrasound, causing the sacrificial electrode to generate more coagulant metal. Additionally, the ultrasound reduces the size of the metal hydroxide which in turn adsorb more contamination in synthetic wastewater. The SEM results show that ultrasound process could successfully remove the passive film on the plates. An intermittent ultrasonic process and double-type reactor were utilized to reduce the breaking of flocs in the system. A total of 97% of the RB19 was removed by intermittent sono-EC treatment at a current density of 18 mA/cm2, a pH of 5, an electrolysis time of 60 min and an ultrasound power of 150 W. Furthermore, the remove of the RB19 in the sono-EC process can be well expressed by a variable-order-kinetic model in the sono-EC system. In conclusion, ultrasonic equipment improves EC performance by removing the passive film.

Perfluorooctanoic acid (C7F15COOH, PFOA) is an aqueous anionic surfactant and a persistent organic pollutant. It can be easily adsorbed onto the bubble-water interface and both mineralized and degraded by ultrasonic (US) cavitation at room temperature. The aim of this study is to investigate whether the effect of US on the degradation of PFOA in solution can be enhanced by the addition of surfactant. To achieve this aim, we first investigated the addition of a cationic (hexadecyl trimethyl ammonium bromide, CTAB), a nonionic (octyl phenol ethoxylate, TritonX-100), and an anionic (sodium dodecyl sulfate, SDS) surfactant. We found the addition of CTAB to have increased the degradation rate the most, followed by TritonX-100. SDS inhibited the degradation rate. We then conducted further experiments characterizing the removal efficiency of CTAB at varying surfactant concentrations and solution pHs. The removal efficiency of PFOA increased with CTAB concentration, with the efficiency reaching 79% after 120 min at 25°C with a 0.12 mM CTAB dose.

Amine-containing pharmaceuticals are the most often detected pharmaceuticals in wastewater and ambient aquatic environments. They can usually be degraded by manganese oxide (MnO2), which is a common natural oxidant in soils. Surfactants often coexist with pharmaceuticals in wastewater. Some amine-containing pharmaceuticals, such as diclofenac (DIC), are acidic and are thus ionic compounds in neutral conditions. These compounds, therefore, have similar properties to surfactants. Surfactants, thus, may influence the adsorption and degradation processes of DIC by MnO2. The effect of the type of surfactant on the degradation of DIC by MnO2 was investigated in this study with the addition of two common biodegradable surfactants (cetyltrimethyl-ammonium bromide (CTAB) and sodium dodecylsulfate (SDS)). The results indicated that the cationic surfactant (CTAB) significantly increased the degradation rate in neutral and alkaline conditions. On the other hand, the anionic surfactant (SDS) slightly increased the DIC removal rate in an acidic condition but significantly decreased the removal in neutral and alkaline conditions. Coexisting cationic surfactants not only influenced the kinetics but also altered the transformation mechanism of DIC by MnO2. Decarboxylation is the main transformation mechanism of DIC in the presence of CTAB, while both decarboxylation and hydroxylation are the main transformation mechanisms in the absence of CTAB.

Amine-containing pharmaceuticals such as acetaminophen, diclofenac, and sulfamethoxazole are the most often detected pharmaceuticals in wastewater and other aquatic environments. Amine-containing pharmaceuticals can be effectively removed by chlorination. These drugs, however, may coexist in wastewater. Thus, they may compete with each other, and their chlorinated products may react with each other to form new products. In this study, competitive effects of the above three amine-containing pharmaceuticals by chlorination and their products were investigated. The priority of chlorination of these compounds was dependent upon the pH of the solution, due to the dissociation of the compounds and hypochlorite. It followed the order of sulfamethoxazole > diclofenac > acetaminophen in an acidic condition, the order of sulfamethoxazole > acetaminophen > diclofenac in a neutral condition, and the order of sulfamethoxazole ≈ acetaminophen > diclofenac in an alkaline condition. Some of the chlorinated products in single- and multiple-compound systems were the same. Dimers of sulfamethoxazole and its chlorinated products, however, were not found, but dimers of sulfamethoxazole and acetaminophen or diclofenac were found in multiple-compound systems. This finding is important because it means that new products may be produced if different amine-containing pharmaceuticals react with free chlorine simultaneously.

This study investigated the direct and indirect electro-oxidation of amine-containing pharmaceuticals (acetaminophen (ACT), diclofenac (DIC), and sulfamethoxazole (SMX)) by using graphite electrodes, and to compare the influence by using different electrolytes (Na2SO4 and NaCl). Under the optimum conditions of current (I) at 0.5 A, in direct system, 74.3%, 90.0%, 81.6% of ACT, DIC, and SMX were respectively removed after 60 min (k = 0.023, 0.037, 0.027 min−1), 48.9%, 85.9%, 68.2% of TOC respectively removed after reaction time. In contrast, at the same current intensity, in indirect system, ACT, DIC, and SMX were eliminated within 30 min (k = 0.117, 0.307, 0.170 min−1), 89.6%, 92.6%, 99.6% of TOC respectively removed after reaction time. The results indicated that the dissociated compounds were attracted to the anode due to electrostatic forces and had higher mass transformation rates in the direct electro-oxidation process. According to the cyclic voltammogram, indirect oxidation occurred when active chlorine species were generated from chloride ions anodically to destroy pollutants. Based on intermediates detected during electro-oxidation treatment by ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), only oxidized intermediates were found in the direct oxidation system, while both oxidized and chlorinated intermediates were found in the indirect oxidation system.

Hand-pressing trials and hand-to-mouth soil transfer experiments were conducted to better understand soil loadings, soil transfer ratios for three mouthing activities, and variations in particle size distributions under various conditions. Results indicated that sand caused higher soil loadings on the hand than clay. When the moisture level of clay soil exceeded its liquid limit, soil loadings also increased. Greater pressing pressures also led to larger clay loadings. Clay with a moisture content close to its plastic limit caused the smallest soil loadings due to strong soil cohesion. Particle sizes of the transferred clay were larger than that of the original clay, indicating that hand-pressing and the pressure exerted may have enhanced clay particles of larger sizes adhering onto the hand. Nevertheless, the sizes of most particles that adhered to the hand were still smaller than 150 μm. Higher pressing pressures and greater moisture contents resulted in larger soil loadings on the hand, and transfer ratios became smaller. Transfer ratios from palm-licking with clay particles were smaller than those from finger-mouthing, which may have been due to finer particles that more readily adhered to the skin of the palm and that were transferred from the hand to the mouth with greater difficulty.

An electrocoagulation flotation (ECF) process was used to remove selected nonsteroidal anti-inflammatory drugs (NSAIDs), specifically diclofenac, ibuprofen, and ketoprofen, from water. A cationic surfactant, cethyltrimethyl ammonium bromide (CTAB), was added to the solution as a collector and frother. Without the addition of the cationic surfactant, the removal of NSAIDs in a single-NSAID solution was in the range of 10–45%; it decreased to approximately 10% in multiple-NSAID systems. However, after adding a stoichiometric amount of CTAB, the removal of NSAIDs significantly improved in single-NSAID systems. For multiple-NSAID removal, the concentration of CTAB required to achieve ideal removal was equal to the sum of the molar concentrations of all the NSAIDs. In addition, a high current density produced smaller bubbles, thus enhanced the electro-flotation and achieved better removal performance. Removal of multiple-NSAIDs in actual hospital wastewater was significantly lower due to interference by oils and other hydrophobic substances.

The effect of calcium on arsenate removal by electrocoagulation with aluminum electrode was investigated in this study. The addition of calcium salt dramatically improved the removal efficiency of As(V). The residual arsenate decreased from more than 0.5 mM to less than 0.05 mM after the addition of stoichiometrically equivalent amounts of calcium salt (γ = 1). The arsenate cannot be completely removed if the γ is under 1. If the γ is over 1, the calcium concentration rose and lead to the increase of hardness. The calcium ions can neutralize the negative surface charges of the precipitate and increase the binding energy of As–O. The addition of calcium also prevented the formation of deposit layer on anode surface which caused an increase of applied potential and decrease the concentration of dissolve aluminum.

This study investigates the photolytic and photocatalytic degradation of dimethyl phthalate (DMP) with novel catalysts including the titanium dioxide–coated magnetic poly(methyl methacrylate) (TiO2/mPMMA) and platinum-doped TiO2/mPMMA microspheres. The experiments under the illumination of ultraviolet (UV) radiation at 185 and 254 nm are conducted to examine the effects of the initial DMP concentration, photocatalyst, and Pt doping on the degradation of DMP and its mineralization efficiency. The photocatalyst and initial DMP concentration are important factors for the degradation of DMP, while the Pt doping has a minor effect. On the other hand, the mineralization efficiency would be significantly accelerated by the presence of photocatalysts and the Pt doping. In addition, it demonstrates the remarkable contribution of UV radiation at 185 nm to the elimination of DMP and intermediates via both direct photolysis and photocatalysis. This study provides useful information about the direct photolytic...

The high turbidity in surface water may make it difficult for water treatment plants to supply drinking water. Chitosan, a natural linear cationic polymer, and aluminum chloride, a metal salt, and the mixture of the two coagulants were used to treat highly turbid raw water in this study according to the residual turbidity, sludge volume and residual aluminum concentration. The residual turbidity was less than 50 NTU but the sludge/water volume ratio was over 150 mL/L after aluminum salt coagulation (135 mg/L as Al), which could stop the sedimentation process. The amount of sludge produced after chitosan coagulation (5 mg/L) was only about 1/5 of that for aluminum coagulation for the similar turbidity removal. Chitosan coagulation, however, still has two problems that need to be solved. First, the residual turbidity of treated water is still too high for sand filtration. Second, the colloid particles may restabilize if chitosan is overdosed. Adding a comparative low dosage of aluminum salt (13.5 mg/L as Al) with chitosan can successfully solve both of the problems. The sludge volume ratio only increased slightly and the residual turbidity was less than 10 NTU. Moreover, the restabilization of colloids did not occur. The residual aluminum concentration, which could lead to Alzheimer’s disease, can also be reduced significantly after addition of chitosan.

To stabilize the copper and aluminum ions in simulated sludge, a series of sintering processes were conducted to transform Cu/Al precipitation into spinel structure, CuAl(2)O(4). The results indicated that the large amount of salt content in the simulated sludge would hinder the formation of crystalline CuAl(2)O(4) generated from the incorporation of CuO and Al(2)O(3), even after the sintering process at 1200 °C. Opposite to the amorphous CuAl(2)O(4), the crystalline CuAl(2)O(4) can be formed in the sintering process at 700-1100 °C for 3 h with the desalinating procedure. According to the theory of free energy, the experimental data and references, the best formation temperature of CuAl(2)O(4) was determined at 900-1000 °C. As the temperature rose to 1200 °C, CuAlO(2) was formed with the dissociation of CuAl(2)O(4). The XPS analysis also showed that the binding energy of copper species in the simulated sludge was switched from 933.8 eV for Cu(II) to 932.8 eV for Cu(I) with the variation of temperature. In this system, the leaching concentration of copper and aluminum ions from sintered simulated sludge was decreased with ascending temperature and reached the lowest level at 1000 °C. Furthermore, the descending tendency coincided with the formation tendency of spinel structure and the diminishing of copper oxide.

The feasibility of stabilizing nickel-laden sludge by a high-temperature NiCr(2)O(4) synthesis process was investigated with different sintering temperatures, salt contents, molar ratios, and reaction atmospheres. The crystalline phases of species were investigated by using an X-ray diffraction, and the surface characteristics of particles were observed by scanning electron microscopy. The leaching behavior of the stabilized sludge was evaluated by Toxicity Characteristic Leaching Procedure (TCLP) test. The results indicated that NiCr(2)O(4) was formed at around 800°C by transforming NiO and Cr(2)O(3) into a spinel structure. Leaching concentrations of both nickel and chromium decreased with an increase in the sintering temperature. The existence of salt in the sludge disturbed the formation of spinel, but a moderate salt content contributed to stabilization efficiency. A Cr/Ni molar ratio2 also contributed to the stabilization efficiency of heavy metals after the thermal process. NiCr(2)O(4) was transformed from simulated sludge under both an N(2) and air atmosphere. The sintering strategy designed for nickel-laden sludge was proven to be beneficial in stabilizing nickel and chromium.

The methanolysis of soybean oil with a K/γ-Al 2 O 3 catalyst using a rotating packed bed (RPB) for the production of fatty acid methyl esters (biodiesel) is presented. The RPB, which provides high centrifugal force and has an adjustable rotational speed, was employed as a novel heterogeneously catalyzed transesterification reactor. The methanol-to-oil molar ratio, the catalyst dosage, the rotational speed of the packed-bed rotator, and the reaction temperature were investigated for their effects on the yield of fatty acid methyl esters ( Y FAME ) in the RPB. Furthermore, the modified first-order reaction kinetics was employed to study the transesterification reaction rate of the K/γ-Al 2 O 3 catalyzed RPB system. In addition, the transesterification performance and durability of the K/γ-Al 2 O 3 catalyst with respect to Y FAME using the RPB system were evaluated, allowing for further comparison with other heterogeneously catalyzed transesterification reactors. Based on the results, the RPB system is considered as a practical, heterogeneously catalyzed transesterification reactor due to its excellent micromixing characteristics.

The feasibility of stabilizing copper-laden sludge by high-temperature CuFe 2 O 4 ferritization process is investigated with different sintering temperature, and the prolonged leaching test. The thermal behavior, structural morphology, phase composition, and phase transformation of the stabilized sludge were investigated by using thermal gravimetry-differential scanning calorimetry, scanning electron microscopy and X-ray diffraction. The leaching behavior of the stabilized sludge under acidic environment was evaluated by modified Toxicity Characteristic Leaching Procedure (TCLP). The results indicated that CuFe 2 O 4 could be effectively formed at around 800 °C by the iron oxide precursor with a 3 h of short sintering. The transformation was discovered on crystallographic spinel structures: the low-temperature (800–900 °C) tetragonal phase (t-CuFe 2 O 4 ) and the high-temperature (∼1000 °C) cubic phase (c-CuFe 2 O 4 ). At higher temperatures (∼1100 °C), the formation of cuprous ferrite delafossite phase (CuFeO 2 ) from the dissociation of CuFe 2 O 4 was also noticed. Both CuFe 2 O 4 spinel and CuFeO 2 delafossite phase have a better intrinsic resistance to acidic environment when compared to that of CuO phase by the modified TCLP test. The sintering strategy designed for copper-laden sludge is proven to be beneficial in stabilizing copper.

The reduction of hexavalent chromium (Cr(VI)) by zero-valent iron (ZVI) is self-inhibiting in near natural groundwater because insulating Fe(III)-Cr(III) (oxy)hydroxide film forms on the ZVI surface during the reaction. This study tries to overcome this deficiency by coating the surface of ZVI with copper to form copper–iron bimetallic particles. The Cr(VI) removal rate by ZVI rose significantly after the copper coating was applied. The copper loading needed for enhancing Cr(VI) removal was much higher than that needed for enhancing removal of chlorinated organic compounds or other oxidative contaminants, because of the higher oxidation potential of Cr(VI). The results of X-ray photoelectron spectroscopy (XPS) indicate that coating copper onto the surface of ZVI can not only increase the deepness of the oxidation film but also increase the oxidation state of iron in the film. This phenomenon means higher Cr(VI) removal capacity per unit weight of ZVI.

The coagulation behavior of aluminum salts in SiO 2(s) -containing chemical mechanical polishing (CMP) wastewater was investigated using jar tests and with reference to the coordination chemistry of Al(III) and Si(IV). The results of the jar tests show that the alum dosage did not influence the removal of silica when more than a particular amount of coagulant was added. However, the removal efficiency of the CMP wastewater depended more strongly on pH than on coagulant dosage. Insight into these results was given by the surface complexation model/surface precipitation model (SCM/SPM) and electrophoresis measurements. Simulation results thus obtained demonstrate that the Al(III) released from the coagulant underwent a two-stage reaction in a narrow range of 1.5 pH under under-saturated solution conditions with respect to the Al-hydroxide solid phase. At low pH (3.5–4.3), the Al(III) prevents the natural dissolution of SiO 2(s) particles by forming bi-nuclear surface complexes which energetically disfavor the simultaneous removal of two metal centers. In the pH range 4.3–5, the surface precipitation reaction dominated, and both Al(III) and Si(IV) formed a new oxide film in the original surface, protecting against dissolution of SiO 2(s) by OH − .

A batch electrocoagulation (EC) process with bipolar electrode and potentiodynamic polarization tests with monopolar systems were investigated as methods to explore the effects of electrode materials and initial solution pH on the As(V) and As(III) removal. The results displayed that the system with Al electrode has higher reaction rate during the initial period from 0 to 25 minutes than that of Fe electrode for alkaline condition. The pH increased with the EC time because the As(V) and As(III) removal by either co-precipitation or adsorption resulted in that the OH positions in Al-hydroxide or Fe-hydroxide were substituted by As(V) and As(III). The pH in Fe electrode system elevate higher than that in Al electrode because the As(V) removal substitutes more OH position in Fe-hydroxide than that in Al-hydroxide. EC system with Fe electrode can successfully remove the As(III) but system with Al electrode cannot because As(III) can strongly bind to the surface of Fe-hydroxide with forming inner-sphere species but weakly adsorb to the Al-hydroxide surface with forming outer-sphere species. The acidic solution can destroy the deposited hydroxide passive film then allow the metallic ions liberate into the solution, therefore, the acidic initial solution can enhance the As(V) and As(III) removal. The over potential calculation and potentiodynamic polarization tests reveal that the Fe electrode systems possess higher over potential and pitting potential than that of Al electrode system due to the fast hydrolysis of and the occurrence of Fe-hydroxide passive film.

A continuous electrocoagulation–flotation (ECF) system was employed to treat synthetic high fluoride-content wastewater following calcium precipitation. The dose of sodium dodecyl sulfate (SDS) in a continuous ECF system was higher than that in the batch system indicating the SDS acted not only as frother, but also as collector in the continuous system. The removal of suspended solids (SS) in the continuous system was less than that in the batch system because the scum was disturbed by the flow of wastewater in the flotation tank. It decreased with the increase in flow rate when the flow rate reaches higher than 800 mL/min, yet it increased with the increase in flow rate when the flow rate falls under 200 mL/min. Two parameters, gas/liquid ratio ( Γ G/L ) and gas/solid ratio ( Γ G/S ), were determined to indicate the discontinuity of the flow and flotation ability, respectively, in order to explain the phenomenon. The result indicates that the flotation ability was insufficient when Γ G/S was under 0.1 L/g and the flow of wastewater became discontinuous when Γ G/L was over 0.4. Both of these situations would lead to the increase of SS.

Objectives The theory of ecological unequal exchange explains how trade and various forms of economic activity create the problem of environmental degradation, and lead to the deterioration of population health. Based on this theory, our study examined the inter-relationship among economic characteristics, ecological footprints, CO2 emissions, infant mortality rates and under-5 mortality rates in low-income countries. Design A longitudinal ecological study design. Setting Sixty-six low-income countries from 1980 to 2010 were included in the analyses. Data for each country represented an average of 23 years (N=1497). Data sources Data were from the World Development Indicators, UN Commodity Trade Statistics Database, Global Footprint Network and Polity IV Project. Analyses Linear mixed models with a spatial power covariance structure and a correlation that decreased over time were constructed to accommodate the repeated measures. Statistical analyses were conducted separately by sub-Saharan Africa, Latin America and other regions. Results After controlling for country-level sociodemographic characteristics, debt and manufacturing, economic activities were positively associated with infant mortality rates and under-5 mortality rates in sub-Saharan Africa. By contrast, export intensity and foreign investment were beneficial for reducing infant and under-5 mortality rates in Latin America and other regions. Although the ecological footprints and CO2 emissions did not mediate the relationship between economic characteristics and health outcomes, export intensity increased CO2 emissions, but reduced the ecological footprints in sub-Saharan Africa. By contrast, in Asia, the Middle East and North Africa, although export intensity was positively associated with the ecological footprints and also CO2 emissions, the percentage of exports to high-income countries was negatively associated with the ecological footprints. Conclusions This study suggested that environmental protection and economic development are important for reducing infant and under-5 mortality rates in low-income countries.

The effect of the molar ratio of hydroxide and fluoride ions to Al(III) ions ( γ OH and γ F ) on coagulation and electrocoagulation (EC) was studied to solve the problem of the over addition of acid or base. The efficiency of defluoridation was approximately 100% when the sum of γ OH and γ F ( γ OH + F ) was close to 3. This finding reveals that the fluoride ions and the hydroxide ions can co-precipitate with Al(III) ions and the formula of the precipitate is AlnFm(OH)3n−m. However, when γ OH was less than 2.4, the defluoridation efficiency, given that γ OH + F = 3 , dropped as γ OH fell, because the amount of aluminum polymer formed dropped. The efficiency of defluoridation of EC exceeded that of coagulation for equal γ OH and γ OH + F , when γ OH + F > 3 , proving the existence of an electrocondensation effect.

This work employs an anodic surfactant, sodium dodecyl sulfate (SDS), to improve the flotation performance of the electrocoagulation-flotation (ECF) process to treated fluoride containing semiconductor wastewater following calcium precipitation. The dissolved fluoride ions and CaF(2) particles in the wastewater after calcium precipitation were effectively removed in the ECF process simultaneously. The dosage of SDS required for ECF was much less than those for dispersed air flotation (DiAF) or dissolved air flotation (DAF) processes because the CaF(2) particles can be collected by hydro-fluoro-aluminum flocs in ECF. Thus, SDS only served as a frother to make the bubbles tiny and stable in the ECF defluoridation process. The interference of co-existing anions can be overcome by increasing the dosage of calcium ions and SDS. The optimum initial acidity for ECF is close to the initial fluoride concentration after calcium precipitation; the amount of SS removed dropped rapidly if the initial acidity exceeded the optimal value because the surface charge of the hydro-fluoro-aluminum particles increased. The initial acidity of the wastewater after calcium precipitation can be modified by changing the [Ca(OH)(2)]/[Ca(2+)](T) ratio and the appropriate ratio is approximately given by the acid dissociation constant of hydrofluoric acid and the initial pH of the wastewater before calcium precipitation.

The kinetics and mechanism ofamoxicillin (AMO) degradation using a 1 x 1 molecular sieve-structured manganese oxide (MnO2) was studied. The presence of the buffer solution (i.e., NaHCO3, NaH2PO4 and KH2PO4) diminished AMO binding to MnO2, thus reducing AMO degradation in the pretest; therefore, all other experiments in this study were conducted without the addition of a buffer. Third-order rate constants, second-order on AMO and first-order on MnO2 increased with elevating pH level (2.81-7.23) from 0.54 to 9.17 M(-2) s(-1), and it decreased to 4.27 M(-2) s(-1) at pH 8.53 beyond the pk(a2) of AMO (7.3). The dissolution of the MnO2 suspension with and without AMO exhibited a similar trend; that is, Mn2+ concentration increased with decreasing pH. However, the dissolution of MnO2 with AMO was greater than that without AMO, except for the reaction occurring at pH 8.53, partially indicating that MnO2 acts as an oxidant in AMO degradation. The preliminary chromatogram data display different products with varying pH reaction s, implying that AMO elimination using this 1 x 1 molecular sieve-structured MnO2 is by adsorption as well as oxidative degradation. A complementary experiment indicates that the amount of oxidatively degraded AMO increases substantially from 65.5% at 4 h to 95% at 48 h, whereas the AMO adsorbed onto MnO2 decreases slightly from 4.5% at4 h to 2.4% at 48 h. The oxidative degradation accounted for more AMO removal than adsorption over the whole reaction course, indicating that the oxidative reaction of AMO on MnO2 dominated the AMO removal.

This study investigated the effects of sulfate ions on the decomposition of perfluorooctanoic acid (PFOA) by ultrasonic (US) irradiation at various pHs, sulfate doses, powers and temperatures. The removal of PFOA was augmented with an increased sulfate ion concentration, with PFOA being almost completely decomposed in 90 min at 25 °C with a sulfate dose of 117 mM. The two major mechanisms in the sulfate-assisted sonochemical system are the direct destruction of PFOA by cavitation and the indirect destruction of PFOA by sulfate free radicals. The decomposition of PFOA followed pseudo-first-order kinetics and was not influenced by pH. The reaction rate constants decreased with increases in temperature due to decreases in the surface tension of the solution.

This study was originally performed to compare the MnO2-based degradation of aqueous methylene blue (MB) under microwave irradiation- (MW-) enhanced and conventional heating- (CH-) enhanced conditions. The degradation process and kinetics were investigated to elucidate the microwave effect on the reaction. The results showed that all three tested conditions, sole MnO2, MnO2/CH, and MnO2/MW, followed the third-order (second upon MB and first upon MnO2) kinetic model. However, a higher degradation rate of MB was available under the MW-enhanced process, which implies that the “athermal effect” of MW might be of more benefit for the generation of electrophilic oxygen ions ( , , and ) to degrade MB. The results showed that the degradation percentage of MB could reach 100%, corresponding to 92% total organic carbon (TOC) removal under microwave irradiation at pH 7.20 for 10 min.

Methylene blue (MB) is a cationic dyestuff, which is particularly resistant to biodegradation. The molecular sieved gamma-MnO2 was used as an adsorbent/oxidant to remove the MB at room temperature and in visible light. The removal efficiency was mainly evaluated by X-ray diffractometer (XRD), UV-Vis spectrometer (UV-Vis), total organic carbon (TOC). The results revealed that the mechanisms of MB removal by gamma-MnO2 are significantly influenced by the pH. In acidic conditions, hypsochromic effects (i.e. blue shifts of UV-Vis spectra) resulting from N-demethylation of the dimethylamino group in MB may occur concomitantly with oxidative degradation by gamma-MnO2. However, the TOC in solution after gamma-MnO2 treatment in acidic conditions did not show a dramatic decrease. At near neutral pH conditions, there was almost no UV-Vis absorption for the MB solution, however, only 50% TOC removal was observed. It indicated that MB was not only adsorbed onto gamma-MnO2 but also partially oxidatively degraded to other organic compounds which were colourless for UV-Vis.

The study reported herein indicated the stabilization mechanisms at work when copper-laden sludge is thermally treated with gamma-alumina and kaolinite precursors, and evaluated the prolonged leachability of their product phases. Four copper-containing phases - copper oxide (CuO), cuprous oxide (Cu(2)O), copper aluminate spinel (CuAl(2)O(4)), and cuprous aluminate delafossite (CuAlO(2)) - were found in the thermal reactions of the investigated systems. These phases were independently synthesized for leaching by 0.1M HCl aqueous solution, and the relative leachabilities were found to be CuAl(2)O(4)

Industrial wastewater sludge was treated by microwave processes to enhance the stabilization of laden copper. The effects of additives, processing time, microwave adsorbents, moisture content, reaction atmosphere, and cooling gas were investigated. The stabilization results were significantly enhanced by metal powder additives, prolonged microwave processing time, proper moisture content, the addition of carbonaceous materials, and a reaction environment with inert gas. It was also found that the moisture content would increase the homogeneity of applied microwave energy, and thus achieve a better overall efficiency between stabilizing agents and copper. The added metal powders may reduce Cu(II) to Cu(0) in the sludge or TCLP. The resulting thermal energy of microwave radiation, and microarcing process and the oxidation heat of Al powder may also assist the transformation of Cu(II) into CuO and CuAl2O4 phases. Part of the sludge was vitrified within inert gas environment when the processing time was longer than 18 min and active carbon dosage was more than 3 g. Reduction reactions also occurred in the hybrid microwave processes, leading to the reduction of sulfates and metal ions, and the formation of Cu2S and FeS. Moreover, the microwave radiation can also enhance the feasibility of co-treating of inorganic and organic solid waste. 2008 Elsevier Ltd. All rights reserved.

The effects of landscape characteristics on surface water quality were evaluated in terms of land-use condition, soil type and slope. The case area, the Chichiawan stream in the Wulin catchment in Taiwan, is Formosan landlocked salmon’s natural habitat. Due to the agriculture behavior and mankind’s activities, the water and environmental quality has gradually worsened. This study applied WinVAST model to predict hydrological responses and non-point source pollution (NPSP) exports in the Wulin catchment. The land-use condition and the slope of land surface in a catchment are major effect factors for watershed responses, including flows and pollutant exports. This work discussed the possible variation of watershed responses induced by the change of land-use condition, soil type and slope, etc. The results show that hydrological responses are highly relative to the value of Curve Number (CN); Pollutant exports have large relation to the average slope of the land surface in the Wulin catchment.

A variable order kinetic (VOK) model derived from the Langmuir equation was applied to specify the kinetics of the fluoride removal reaction for electrocoagulation (EC). Synthetic solutions were employed to elucidate the effects of the initial fluoride concentration, the applied current and the initial acidity on the simulation results of the model. The proposed model successfully describes the fluoride removal reaction, except in a system in which the initial concentration of the acid is less than the initial fluoride concentration. The violent change of pH companying with the appearance of equivalence point in the titration curves should be the main reason the VOK model fails to simulate the defluoridation in the systems with an initial acidity higher than initial fluoride concentration.

Both surface treatments, H2-reducing pretreatment at 400 degrees C and the deposition of copper as a catalyst, were attempted to enhance the removal of nitrate (40 (mg N) L(-1)) using zerovalent iron in a HEPES buffered solution at a pH of between 6.5 and 7.5. After the iron surface was pretreated with hydrogen gas, the removal of the passive oxide layers that covered the iron was indicated by the decline in the oxygen fraction (energy dispersive X-ray analysis) and the overlap of the cyclic polarization curves. The reaction rate was doubled, and the lag of the early period disappeared. Then, the deposition of copper onto freshly pretreated iron promoted nitrate degradation more effectively than that onto a nonpretreated iron surface, because of the high dispersion and small size of the copper particles. An optimum of 0.25-0.5% (w/w) Cu/Fe accelerated the rate by more than six times that of the nonpretreated iron. The aged 0.5% (w/w) Cu/Fe with continual dipping in nitrate solution for 20 days completely restored its reactivity by a regeneration process with H2 reduction. Hence, these two iron surface treatments considerably promoted the removal of nitrate from near-neutral water; the reactivity of Cu/Fe was effectively recovered.

Batch experiments with bipolar aluminum electrodes and potentiodynamic polarization tests with monopolar systems were conducted to investigate the effects of the type and concentration of co-existing anions on defluoridation in electrocoagulation (EC) process. The results demonstrate that the type of the dominant anion directs the EC defluoridation reaction. The defluoridation efficiency was almost 100% and most of the fluoride removal reaction occurred on the surface of the anode in the solution without the co-existing anions, due to the electro-condensation effect. In the solutions with co-existing anions, most of the defluoridation took place in bulk solution. The residual fluoride concentration is a function of the total mass of Al(III) liberation from anodes and the types of the functions in the solutions with and without co-existing anions are different. The existence of sulfate ions inhibits the localized corrosion of aluminum electrodes, leading to lower defluoridation efficiency because of lower current efficiency. The presence of chloride or nitrate ions prevented the inhibition of sulfate ions, and the chloride ions were more efficient. Different corrosion types occurred in different anion-containing solutions and the form of corrosion affected the kinetic over-potential. The bypass flow causes the decrease of current efficiency and the proportion of the bypass flow of current increased due to a rise of the kinetic over potential and the conductivity of the solution.

An indicator model for evaluating trends in river quality using a two-stage fuzzy set theory to condense efficiently monitoring data is proposed. This candidate data reduction method uses fuzzy set theory in two analysis stages and constructs two different kinds of membership degree functions to produce an aggregate indicator of water quality. First, membership functions of the standard River pollution index (RPI) indicators, DO, BOD5, SS, and NH3-N are constructed as piecewise linear distributions on the interval [0,1], with the critical variables normalized in four degrees of membership (0, 0.33, 0.67 and 1). The extension of the convergence of the fuzzy c-means (FCM) methodology is then used to construct a second membership set from the same normalized variables as used in the RPI estimations. Weighted sums of the similarity degrees derived from the extensions of FCM are used to construct an alternate overall index, the River quality index (RQI). The RQI provides for more logical analysis of disparate surveillance data than the RPI, resulting in a more systematic, less ambiguous approach to data integration and interpretation. In addition, this proposed alternative provides a more sensitive indication of changes in quality than the RPI. Finally, a case study of the Keeling River is presented to illustrate the application and advantages of the RQI.