Coagulation Technology Research Articles

Enhanced ballasted magnetic coagulation process based on one-step pyrolysis synthesis of sludge-derived AC@MNPs for advanced purification of secondary effluent from wastewater treatment plants: specific removal of low molecular weight organic matter

The removal of dissolved organic matter from secondary effluent in sewage treatment is a significant challenge, necessitating the development of green and efficient composite magnetic materials for coagulation. In this study, activated carbon-modified magnetite nanoparticles (AC@MNPs) were synthesized via one-step activation pyrolysis using iron sludge as a precursor. The ballast coagulation process employed AC@MNPs as both magnetic species and adsorbent, with polymeric aluminum chloride (PACl) as a coagulant, for advanced treatment of secondary effluent. A response surface methodology identified optimal pyrolysis conditions: an activation ratio (KOH/ST) of 1.2, a pyrolysis time of 1 h, and a temperature of 640 °C. The influence of pyrolysis temperature (600 ∼ 700 °C) on the morphology and pore characteristics of AC@MNPs was investigated, highlighting its significance in coagulation performance. Characterization through XRD, VSM, and FTIR confirmed the favorable settling properties of the composite magnetic flocs and recyclability of AC@MNPs. Coagulation experiments revealed a synergistic effect of AC@MNPs and PACl, enhancing the removal of UV254 and COD from 33.4 % and 36.2 % (with PACl alone) to 74.02 % and 76.53 %, respectively. The overall performance of the ballast coagulation process was evaluated, demonstrating effective removal of organics of various molecular weights. Finally, the coagulation mechanism was systematically discussed. Overall, this research offers insights into the application of magnetic coagulation technology for wastewater treatment advancements.

Optimization of navigation laser coagulation technology of the retina for active retinopathy of prematurity

Optimization of navigation laser coagulation technology of the retina for active retinopathy of prematurity

Experimental study on surface optimization of dosage in magnetic coagulation process for enhancing primary treatment of urban sewage

This work aims to investigate the minimum dosage required to achieve optimal removal of carbon, nitrogen, and phosphorus in the Chemical Enhanced Primary Treatment (CEPT) process using magnetic coagulation technology. A response surface methodology was adopted to generate multiple regression models to optimize the dosages of three types of coagulation, i.e., polyaluminum chloride (PAC), polyacrylamide (PAM), and magnetic medium Fe3O4 particles (MP), based on the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), and total phosphorus (TP). The results showed that the regression models could predict results well with actual engineering results. Compared to the traditional coagulation process, the synergistic enhancement of PAC+PAM+MP in the CEPT process significantly improved the treatment effects. Based on the COD removal rates, PAC performed better than MP, followed by PAM; likewise, for the NH3-N and TP removal rates, PAC outperformed PAM, followed by MP. The optimized PAC, PAM, and MP dosages were 135.87, 1.51, and 108.36 mg/L, respectively, reaching 92.27 % COD, 71.98 % NH3-N, and 91.33 % TP removal rates with less than 5 % errors compared to the experimental verification results. These optimization models offer a practical and cost-saving reference for enhancing the primary treatment effect on carbon, nitrogen, and phosphorus removal using PAC+PAM+MP.

Transforming contaminant ligands at water–solid interfaces via trivalent metal coordination

In environmental matrices, the migration and distribution of contaminants at water–solid interfaces play a crucial role in their capture or dissemination. Scientists working in environmental remediation and wastewater treatment are increasingly aware of metal–contaminant coordination; however, interfacial behaviors remain underexplored. Here, we show that trivalent metal ions (e.g. Al3+ and Fe3+) mediate the migration of pollutant ligands (e.g. tetracycline (TC) and ofloxacin) to the organic solid interface. In the absence of Al3+, humic acid (HA) colloids (50 mg/L) capture 26.1 % of the TC in water (initial concentration: 10 mg/L) via weak intermolecular interactions (binding energy: −5.71 kcal/mol). Adding Al3+ (2.5 mg/L) significantly enhances the binding of TC to an impressive 94.2 % via Al3+ mediated coordination (binding energy: −84.89 kcal/mol). The significant increase in binding energy results in superior interfacial immobilization. However, excess free Al3+ competes for TC binding via direct binary coordination, as confirmed based on the unique fluorescence of Al3+–TC complexes. Density functional theory calculations reveal the intricate process of HA–Al3+ binding via carboxyl and phenolic hydroxyl sites. The HA–Al3+ flocs then leverage the remaining coordination capacity of Al3+ to chelate with TC. As well as providing insights into the pivotal role of metal ion on the self-purification of natural water bodies, our findings on the interfacial behavior of metal–contaminant coordination will propel coagulation technology to the capture of microscale pollutants.

Combined extraction of manganese during water purification of technogenic solutions

A method for demanganization of technogenic aqueous solutions is presented. This method involves electrocoagulation purification of aqueous systems from high metal contents and extraction of manganese (II) ions by carbon sorbent adsorption. A coagulation technology based on electrogenerated aluminum hydroxide was used. According to diffraction analysis, such a hydroxide exhibits an amorphous porous hydrogel structure with a developed sorbing surface. The micellar structure of the as-generated aluminum hydroxide, which was attributed to a modification of gibbsite, is represented by the following colloidal particle: {[m Al(OH)3] nAl(OH)2+ (n-x) OH-}x+ xOH-. The associative process of sorption on gibbsite occurs by dispersion interaction, which is governed by the force of electrostatic attraction of instantaneous and induced dipoles of electrically neutral sorbent molecules and the [Mn (OH2)2(OH)2]0 manganese hydroxo-aquo complex. The adsorption limiting value of manganese ions amounted to 4.9 mmol/g at 298 K and pH 5.8, with the adsorption equilibrium constant reaching 1.36 . 104. The electricity consumption corresponded to 12.0 А.h at an optimal electrocoagulation duration of 15 min and a current density of 1.6 мА/сm2. The final purification of aqueous solutions using carbon sorbents was conducted in a slightly alkaline medium at pH 7.5. The manganese sorption value reached 1.68 mmol/g. Therefore, the resource-saving effect of processing of technogenic hydro-mineral solution is manifested in a significant reduction of heavy metal salts and in obtaining of demanded mixed coagulants of aluminum and iron sulfates from water purification wastes. Another positive effect of electrochemical water purification consist in water disinfection and its improved ogranoleptic parameters.

Defluoridation of drinking water by using low cost point of use treatment technologies: A review

Fluoride is an anionic pollutant found in surface or ground water in large quantities due to various human activities, for examples, disposal of industrial wastewater or geochemical reactions. The presence of fluoride in drinking water above certain limits has intense effects on human health. It strengthens the tooth enamel to a small level (1.0-1.5 mg/L). In drinking water, the presence of fluoride in the range of 1.5 to 4.0 mg/L may give rise to dental fluorosis at initial the stage, while the continuous exposure to high fluoride concentrations (4.0-10.0 mg/L) leads to skeletal fluorosis. In many countries of the world, including Pakistan, fluoride exists in ground water in high concentration, reaching above 30.0 mg/L on a large scale. The objective of writing this article is to offer accurate information on the efforts of a number of scholars who worked on fluoride removal from drinking water. The fluoride removal techniques have been categorized into two parts dealing with coagulation/precipitation and adsorption. Lime and alum (Nalgonda technique) and chitin have been discussed under coagulation technologies, while adsorption deals with a number of adsorbents, i.e., activated carbon, activated alumina, saw dust, bone char, rice husk ash, bauxite, tea-ash, and kaolin. Each technique discussed can remove fluoride under certain conditions. Each treatment technology has its limitations, and since there is no technology that can achieve its purpose in diverse conditions, the choice of fluoride removal techniques should be according to a specific site, depending on fundamental conditions and the needs of the local area.

Эволюция транспупиллярной лазерной коагуляции сетчатки в лечении активной ретинопатии недоношенных: от режима одиночного импульса до навигационного сопровождения

Abstract Evolution of transpupillary laser coagulation of the retina in the treatment of active retinopathy of prematurity: from single pulse mode to navigational support A.V. Tereshchenko, I.G. Trifanenkova, Yu.A. Sidorova, V.V. Firsova, V.V. Shaulov S. Fyodorov Eye Microsurgery Federal State Institution, Kaluga branch, Kaluga, Russian Federation K.E. Tsiolkovski Kaluga State University, Kaluga, Russian Federation Purpose. To present the development stages and results of 18 years of experience in laser technologies application for the treatment of premature infants with active ROP in the Kaluga branch of S. Fyodorov Eye Microsurgery Federal State Institution. Material and methods. Transpupillary laser coagulation of the retina (LCR) was performed in 1583 children (2537 eyes) with active ROP for the period from 2004 to 2021. LCR was carried out with various stationary laser ophthalmocoagulators. Stages 2 and 3 of active ROP with an unfavorable disease course, stage of early clinical manifestations, manifestation of aggressive posterior ROP were indications for laser treatment. Results. Transpupillary LCR began to be performed for children with active ROP with a stationary ophthalmic coagulator for the first time in Kaluga branch of the S. Fyodorov Eye Microsurgery in 2004. The technology of patterned LCR in active ROP was applied for the first time at domestic and international clinical practice, in the Kaluga branch of Eye Microsurgery in 2009. Pattern LCR began to be performed on the Integre Pro Scan device in 2016. Pattern with the most dense and uniform arrangement of laser applications – hexagonal – was identified. In 2021 transpupillary LCR of the avascular zone of the retina was performed in automatic mode with navigation support on the Navilas 577s laser system. It was possible to perform LCR of the avascular zone of the retina up to the dentate line in all cases. Regression of disease was achieved in 100% of cases. Conclusion. Evolution of laser technologies and the experience of their use demonstrate the high efficacy, safety and predictability of the results of laser treatment of active ROP. Modern pattern laser techniques are highly effective, safe, dosed and tissue-saving, which can serve as the basis for standardization of retinal laser coagulation technology in the treatment of active ROP. Key words: retinopathy of prematurity, unfavorable type of course, laser coagulation of the retina, hexagonal pattern, navigation system

Synthesis and evaluation of a novel cross-linked biochar/ferric chloride hybrid material for integrated coagulation and adsorption of turbidity and humic acid from synthetic wastewater: Implications for sludge valorisation

The deep removal of organic pollutants is challenging for coagulation technology in drinking water and wastewater treatment plants to satisfy the rising water standards. Iron (III) chloride (FeCl3) is a popular inorganic coagulant; although it has good performance in removing the turbidity (TB) in water at an alkaline medium, it cannot remove dissolved pollutants and natural organic matter such as humic acid water solution. Additionally, its hygroscopic nature complicates determining the optimal dosage for effective coagulation. Biochar (BC), a popular adsorbent with abundant functional groups, porous structure, and relatively high surface area, can adsorb adsorbates from water matrices. Therefore, combining BC with FeCl3 presents a potential solution to address the challenges associated with iron chloride. Consequently, this study focused on preparing and characterizing a novel biochar/ferric chloride-based coagulant (BC–FeCl3) for efficient removal of turbidity (TB) and natural organic matter, specifically humic acid (HA), from synthetic wastewater. The potential solution for the disposal of produced sludge was achieved by its recovering and recycling, then used in adsorption of HA from aqueous solution. The novel coagulant presented high TB and HA removal within 10 min of settling period at pH solution of 7.5. Furthermore, the recovered sludge presented a good performance in the adsorption of HA from aqueous solution. Adsorption isotherm and kinetics studies revealed that the Pseudo-second-order model best described kinetic adsorption, while the Freundlich model dominated the adsorption isotherm.

Mechanism of the green coagulation processes on the construction of raw rubber network structure

AbstractAcid coagulation is the most traditional latex coagulation technology, but this coagulation process leads to delayed vulcanization, corrosiveness, and environmental pollution. Different coagulation processes significantly impact the raw rubber network structure, leading to differences in the properties of both raw rubber and rubber vulcanizates. Raw rubber was prepared by three acid‐free coagulation processes: freeze, microwave, and flash drying. The network density, molecular chain flexibility, molecular weight, processing fluidity, and plasticity retention of the raw rubber were characterized, and the vulcanization characteristics, viscoelasticity, mechanical properties, and dynamic mechanical properties of the cured rubber composites were investigated. Raw rubbers prepared by microwave drying and flash drying had higher crosslink density, more flexible molecular chains, larger molecular weight, and wider molecular weight distribution, thereby increasing the crosslink density of rubber vulcanizates. The crosslink density of the raw rubber prepared by microwave drying versus the acid coagulated raw rubber increased by 51% to 105.71 mol/m3, the tensile strength increased by 16% to reach 28.12 MPa, and the elastic modulus and rolling resistance under dynamic stress increased. This paper provides a new idea for analyzing the relationship between the raw rubber network structure and the properties of vulcanized rubber.Highlights Acid‐free raw rubbers are prepared by freeze, microwave, and flash drying. Coagulation processes significantly impact the raw rubber network structures. Effects of raw rubber network structures on properties are investigated. Crosslink density, plasticity retention, and tensile strength are improved.

Abstract PO5-19-09: Trial in progress: A prospective randomized, controlled study to evaluate device efficacy for cutting and/or coagulation of tissue during mastectomy procedures

Abstract Background/Purpose: The ConMed HelixAR Electrosurgical Generator with Argon Beam Coagulation Technology (CHEST) trial aims to focus on patients undergoing mastectomy, either unilateral or bilateral, with immediate breast reconstruction including breast implants, tissue expander placement, or autologous flap. The study design follows the standard of care procedure with device efficacy being measured between two devices regularly used in the operative setting: the HelixAR Electrosurgical Generator (HEG) and the Conventional Electrosurgical Coagulation (CEC) systems. The need for safe alternative surgical tools is increasing as the number of women needing surgical treatment increases. Allowing for the test and comparison of these standardized devices gives an extent to the advantages of using one over the other. To evaluate the device effectiveness between the HelixAR Electrosurgical Generator and Conventional Electrosurgical Coagulation systems for cutting and/or coagulation of tissue during mastectomy and reconstruction surgery, we report the implementation in a randomized clinical trial. The study is powered to show superiority of the HEG to the CEC as it relates to the primary objective of time from post-mastectomy to hemostasis. The HEG is designed to deliver argon gas and high frequency electrical current compared to the CEC delivering high frequency electrical current only. The primary efficacy measure is the time it takes from post-mastectomy to hemostasis with the secondary effectiveness endpoints being infection, drain duration, total drain output, blood loss and device related adverse events. The study hypothesizes that the time for post-mastectomy hemostasis is significantly less for the HEG than the CEC. Additional hypotheses include overall less device related adverse events, lower blood loss, and reduced operative time in favor of the HEG. Methods: This is a prospective 1:1 randomized controlled study of the HEG versus the CEC for patients undergoing a mastectomy with reconstruction procedure. 82 patients will be enrolled and distributed in two arms of 41 patients with a primary objective to assess the device efficacy for cutting and coagulation. The subject population includes patients with breast cancer or high risk from genetic mutations and/or family history. Exclusion factors include known history of bleeding diathesis or coagulopathy, advanced refusal of blood transfusion, active systemic or cutaneous infection or inflammation. The enrolled patients will be followed for 2 months post-operatively. Results: The study is open with 53/82 (65%) patients enrolled at the time of the abstract submission. Of those, 26 subjects were randomized to the CEC and 27 to the HEG. 27 subjects have experienced an adverse or serious adverse event including bruising, infections, and wound dehiscence, none determined to be related to the device use. For the study, analysis will focus on the primary endpoint comparing post–mastectomy procedure time to hemostasis between the two devices. Conclusion: The CHEST trial demonstrates the feasibility of conducting a randomized controlled trial at a single center in a complex operative setting comparing two surgical modalities. The testing of these surgical devices provides rationale for the implementation of safe and regulated clinical trials. While both devices are FDA approved and regularly used, the standardization of device efficacy is becoming more prevalent as new innovations get introduced into the surgical setting. Citation Format: Jessica Montalvan, Ivan Marin, Logan Healy, Margarita Riojas-Barrett, Mary Bajomo, Elizabeth Bonefas, Alastair Thompson, Marco Maricevich, Sebastian Winocour, Stacey Carter. Trial in progress: A prospective randomized, controlled study to evaluate device efficacy for cutting and/or coagulation of tissue during mastectomy procedures [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-19-09.

New Approaches to Surgical Treatment of Patients with Advanced Stage of Proliferative Diabetic Retinopathy

Purpose. Development and evaluation of the clinical effectiveness and safety of a vitrectomy (VE) technique for patients with advanced stage proliferative diabetic retinopathy (ASPDR).Materials and methods. We observed 132 patients (mean age 62.8 ± 2.4 years) with the following criteria for inclusion in the study, corresponding to the classification criteria of ASPDR: it is impossible to estimate the area of neovascularization; the fundus of the eye is partially ophthalmoscoped or not ophthalmoscoped in the posterior pole; preretinal or vitreal hemorrhage in the posterior pole with an area of more than 4 optic discs; retinoschisis in the macular zone. All patients were divided into the following two groups, equal in age, gender and visual status of the “healthy” eye: the main group (MG, 69 patients, 69 eyes), who underwent VE was performed according to the developed method and a control group (CG, 63 patients, 63 eyes), in which VE was performed according to the traditional method.Results. The incidence of intraoperative complications in patients in the MG (5.8 %) was 8.1 % (p < 0.05) lower than in the CG (13.9 %). The incidence of postoperative complications in patients from the MG (5.5 ± 0.5 %) was 4.2 % (p < 0.01) lower than in the CG (9.7 ± 1.0 %). The increase in best-corrected visual acuity after surgery in patients from the MG was significantly (by 0.13 rel. units, p < 0.001) higher than in the CG. The value of the average decrease in the developed qualitative criteria for the condition of the fundus in patients in the MG (1.6 ± 0.1) was 23.1 % (p < 0.05), higher than in the CG (1.3 ± 0.1).Conclusion. Surgical treatment of patients with ASPDR using the developed technique provides (compared to the traditional approach) a higher level of safety and clinical effectiveness. The main advantage of the developed technique is an integrated approach to surgical intervention, including the improvement of ophthalmological “techniques” (use of one-stage combined surgery, endolaser coagulation technology, etc.) and drug support (administration of ranibizumab at a dose of 0.05 mg 3–5 days before surgery) and the choice of intravenous sedation as the optimal anesthetic aid.

Study on the efficiency of the preoxidation–coagulation process in removing disinfection by-product precursors from micropolluted water

The efficiency of preoxidation–coagulation technology in removing disinfection by-product precursors and organic compounds from polluted surface water and the effect of this technology on the generation of disinfection by-products are explored.

Design and implementation of control system for electroplating wastewater treatment by photovoltaic energy sinusoidal alternating current coagulation technology

A novel photovoltaic energy-sinusoidal alternating current coagulation (PE-SACC) system was proposed for the removal of heavy metal ions (HMs) in electroplating wastewater. A response surface methodology was used to study the combined effect of two factors on removal efficiency (Re) and energy consumption (EEC), and the optimal process parameters were obtained. The morphology, surface element content, crystal structure, and chemical composition of the flocs generated during the electrocoagulation (EC) process were characterized using SEM, EDS, XRD, FTIR, and XPS techniques. The intra-particle diffusion model was used to describe the adsorption behavior of HMs (Cu2+, Zn2+ and Ni2+) by flocs. Finally, the removal mechanism of HMs by SACC technology and its application in actual wastewater treatment were discussed in detail. The results revealed that when c0(Ni2+) = c0(Zn2+) = c0(Cu2+) = 50 mg·dm−3, cCl− = 100 mg·dm−3, pH0 = 10, j = 1.3 A·m−2, t = 85 min, the Re(Cu2+), Re(Zn2+) and Re(Ni2+) were 99.3%, 99.1%, and 98.4%, respectively, and the EEC was 0.105 kWh·m−3. Compared with the traditional direct current coagulation (DCC), EEC, electrode consumption, and sludge production in SACC mode were reduced by 37.1%, 62.2%, and 66.6%, respectively. The PE-SACC system achieved ultra-low cost treatment of heavy metal electroplating wastewater. The adsorption process included surface adsorption, pore adsorption, and adsorption equilibrium. The mechanisms for the removal of HMs included cathode reduction, alkaline precipitation, and adsorption. In the actual wastewater treatment process, the removal efficiency of HMs could still be maintained above 99%, and the effluent met the national discharge standard (GB 31574–2015). This study presented an economically and environmentally sustainable approach for the evolution and industrial utilization of novel electrocoagulation technologies.

Coagulation technologies for separation of microplastics in water: current status

The pollution of the microplastics in the water environment has already been a threat to the whole ecosystem. Numerous MPs are detected in the ocean and the treated wastewater from the wastewater treatment plant. Due to its small particle size, MPs are proven to penetrate through animal cells and cause even fatal harm to the aminal itself. These reports discuss how well the coagulation behaves in MPs’ separation from the water environment and what factors could affect the MPs’ separation efficiency using coagulation. Recent studies about the coagulation used in MPs separation from water has been reviewed, and the MPs removal efficiency for conventional coagulation and electro-coagulation is determined to be 8.28% to 98.2% and 8.24% to 99.4% respectively. The result and conclusion of this study hopefully provide references for people who study the MPs in water and its management strategy in the future.

Microcosmic mechanism analysis of the combined pollution of aged polystyrene with humic acid and its efficient removal by a composite coagulant

The composite pollutants formed by aged polystyrene (APS) and natural organic matter are complex and harmful, which lead to the deterioration of water quality. In this work, the interaction mechanism between humic acid (HA) and APS was discussed by investigating the changes in their functional groups. Besides, a novel polyaluminum-titanium chloride composite coagulant (PATC) was prepared, and its binding behaviors with HA@APS under different pH conditions were analyzed from a microscopic perspective. It was found that at pH 4, π-π conjugation was the dominant interaction between HA and APS. And the main removal mechanism of HA@APS by PATC was surface complexation. With the increase of pH, π-π conjugation, n-π electron donor-acceptor interaction (EDA), and hydrogen bonding gradually dominated the interaction between APS and HA. At pH 7, PATC hydrolyzed to form various polynuclear Al-Ti species, which could meet the demand for different binding sites of HA@APS. Under alkaline conditions, HB and n-π EDA in HA@APS were weakened, while π-π conjugation held a dominant position again. At this time, the main coagulation mechanism of PATC changed from charge neutralization to sweeping action, accompanied by hydrogen bonding. Environmental ImplicationMicroplastics (MPs) have attracted the public’s attention due to their potential toxicity to humans. The combined pollution of aged microplastics and humic acid (HA) will bring great harm to aquatic environment. The development of novel composite coagulants is hopeful to efficiently remove MPs and their combined pollutants. Elucidating the interactions between HA and aged MPs is helpful to understand the transformation and fate of MPs in actual environments, and to reveal the removal mechanism of composite pollutants by coagulation. The findings presented here will provide theoretical guidance for addressing the challenges of coagulation technology in treating new pollutants in practice.

Using N-TiO2 to enhance the coagulation of Oscillatoria sp. and subsequently degrade cells and their metabolites in sludge under visible light

Oscillatoria, a common genus of filamentous cyanobacteria, has unsatisfactory removal efficiency in drinking water treatment plants, and the cyanobacteria will accumulate and release cyanotoxins into the sludge. This study therefore used photocatalyst particles (nitrogen-doped TiO2 (N-TiO2)) as ballast to enhance the coagulation of Oscillatoria sp. and to degrade both the cells and the metabolites in sludge by visible-light photocatalysis. Results show that combining 100 mg/L N-TiO2 with different coagulants (polyaluminium ferric chloride (PAFC), FeCl3, or AlCl3) was able to improve the Oscillatoria sp. removal efficiency of coagulation to 95 %, and there were no floating flocs. The addition of N-TiO2 resulted in less-negative electrokinetic potentials of Oscillatoria sp. aggregates, enhanced the adsorption bridging effect, and increased the density and compactness of flocs. N-TiO2 had little effect on the integrity of Oscillatoria sp. cells and did not cause the release of cylindrospermopsin (CYN) during coagulation. In the photocatalysis of Oscillatoria-laden sludge 100 mg/L N-TiO2 effectively inactivated Oscillatoria sp. cells within 48 h, regardless of the type of coagulant. After photocatalytic treatment the cell wall was rough and deformed and most of the cell cytoplasm had been removed. Furthermore, the content of extracellular organic matter in sludge supernatant was significantly reduced. After the 48-h treatment 89.2 % of total CYN in the sludge was able to be degraded. This study therefore suggests that N-TiO2 enhances coagulation technology can not only improve the efficiency of removal of filamentous cyanobacteria, but also reduce the ecological risk of sludge discharge and facilitate the reuse of sludge supernatant.

Electrochemical treatment of real cotton fabric industry wastewater using copper and stainless steel electrodes

Abstract Real cotton fabric industry wastewater (CFIWW) was treated using the novel electrochemical coagulation (ECC) technology by stainless steel (SS) and copper (Cu) electrodes for applied cell current 1.5 and 4.4 A for a maximum electrolysis time of 30 min. Pre-characterization of CFIWW before ECC showed higher values of chemical oxygen demand (COD), colour, chloride, alkalinity and other quality parameters. Removal of COD and total dissolved solids (TDS) was 97 and 94% for 30.2 V and 4.4 A while using a Cu electrode. The ECC obtained sludge produced 3.13 g/L for Cu and 11.2 g/L for SS for 4.4 A, and 0.43 and 3.98 g/L for 1.5 A. The analysis of ECC sludge was conducted using a scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FT-IR). The SEM images of ECC sludge showed unstructured, irregular morphology with uneven edges and rough surfaces. The elemental composition of sludge was studied using EDS showing the presence of copper, oxygen, sodium, sulphur and iron. The FT-IR spectra of ECC sludge for Cu- and SS-mediated ECC-generated sludge showed the presence of alcohol and carboxyl groups at several wave numbers. The specific energy consumption (SEC) for Cu was lower than SS.

Experimental and numerical study on the acoustic coagulation of charged particles

Coagulation technology is widely used as a dust removal technology pre-treatment. The mechanism of particle coagulation and charging under the coupling of the electric field and the acoustic field is investigated in this paper. The movement law of the acoustic field waveform, sound pressure level and acoustic field flow rate parameters on the particles are analyzed numerically using COMSOL Multiphysics software, and the operating parameters for the best coagulation effect of charged particles are obtained through experimental studies. The results show that the higher the supply voltage, the more the particles are charged and the better the particle coagulation effect. The higher the sound pressure level, the better the particle coagulation effect. The acoustic frequency is not linearly related to the particle coagulation efficiency. An optimal operating parameter is obtained. The acoustic and electric field coupling resulted in a particle reduction rate of 0.62 and a significant particle coagulation effect. • The mechanism of particle coagulation under the coupling effect of acoustic and electric fields is studied. • The effect of different acoustic field parameters on the particle motion pattern in the furnace is simulated. • The optimal acoustic field parameters are obtained. • The particle reduction rate reaches 0.62.

Determination of sorption characteristics of aluminum hydroxide sludge formed at the stage of pre-purification of water treatment plant

An urgent task of the research is to describe the properties of the sludge formed during coagulation depending on the type of water supply source. Namely, the aim is to study the sorption capacity of the sludge for the main components removed from the water (iron compounds, organic substances, and silicic acid compounds). This indicator allows you to directly determine the effectiveness of the coagulation. When comparing the actual values of this indicator with practically obtainable values, one can say about the lack or excess of the coagulant supplied for processing. To calculate the specific sorption capacities of the sludge, the following indicators have been used: organic content, the weight concentration of silicic acid compounds in terms of SiO2 and the weight concentration of iron compounds in terms of Fe. After drying and calcining the sludge, the resulting mineral residue has been dissolved in the solution, and the content of the final components was determined. Conventional water analysis methods have been applied. For the first time, a method is proposed to determine the specific sorption capacities of aluminum hydroxide sludge for organic compounds, for iron compounds in terms of Fe, for silicic acid compounds in terms of SiO2. A classification of natural low-turbidity waters with an increased content of iron-organic compounds is proposed. Within the framework of the proposed classification of waters, the authors have obtained previously undetermined actual specific sorption capacities of the sludge. Recommendations have been given to get practical importance values of the sorption characteristics of the sludge. The proposed method to calculate the sorption capacity of aluminum hydroxide sludge and index of sorption capacity of the sludge are recommended to be used as a parameter that determines the conditions and efficiency of application of the aluminum sulfate coagulation technology. Excessive doses of the coagulant that provide a sorption capacity of the sludge greater than the recommended values, lead to an excessive consumption of both the reagent itself and purge water. Thus, some measures can be taken to bring the sorption capacity of the sludge to practically achievable values, for example, aquatic acidification.

Design and coagulation mechanism of a new functional composite coagulant in removing humic acid

The deep removal of organic pollutants is a challenging task for coagulation technology in the drinking water and wastewater treatment plants to satisfy the rising water standards. To obtain high removal efficiency for organic matter (OM), a novel coagulant, Fe-PAA, was developed based on ferric salts and polyacrylic acid (PAA) in this study, which contained long flexible carbon chain and positive coordination sites. The humic acid (HA) was employed as a representative OM target with wide molecular weight range in the coagulation tests. The coagulant Fe-PAA with Fe3+/COOH ratio of 1:1 exhibited the promising coagulation performance meeting with the initial design principle. Compared to ferric chloride, Fe-PAA-1:1 exhibited overall advantages on HA removal, formation of large and compact flocs, and control of residual Fe3+. As a macromolecular coagulant, Fe-PAA-1:1 demonstrated the synergetic advantages of iron hydrolysis components and flexible long-chain polymers. The charge neutralization and bridging effects dominated coagulation process under acidic condition, while complexation and bridging effects were the main driving force of Fe-PAA-1:1 under neutral and alkaline conditions for HA removal. Overall, this study provides revelatory information for the development of a new kind of highly efficient and cost-effective coagulant to satisfy the demand of current water treatment.