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"Sewage Purification Ion exchange process."
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New trends in removing heavy metals from wastewater
With the development of researches, the treatments of wastewater have reached a certain level. Whereas, heavy metals in wastewater cause special concern in recent times due to their recalcitrance and persistence in the environment. Therefore, it is important to get rid of the heavy metals in wastewater. The previous studies have provided many alternative processes in removing heavy metals from wastewater. This paper reviews the recent developments and various methods for the removal of heavy metals from wastewater. It also evaluates the advantages and limitations in application of these techniques. A particular focus is given to innovative removal processes including adsorption on abiological adsorbents, biosorption, and photocatalysis. Because these processes have leaded the new trends and attracted more and more researches in removing heavy metals from wastewater due to their high efficency, pluripotency and availability in a copious amount. In general, the applicability, characteristic of wastewater, cost-effectiveness, and plant simplicity are the key factors in selecting the most suitable method for the contaminated wastewater.
Journal Article
Recent Progress of Layered Double Hydroxide-Based Materials in Wastewater Treatment
Layered double hydroxides (LDHs) can be used as catalysts and adsorbents due to their high stability, safety, and reusability. The preparation of modified LDHs mainly includes coprecipitation, hydrothermal, ion exchange, calcination recovery, and sol–gel methods. LDH-based materials have high anion exchange capacity, good thermal stability, and a large specific surface area, which can effectively adsorb and remove heavy metal ions, inorganic anions, organic pollutants, and oil pollutants from wastewater. Additionally, they are heterogeneous catalysts and have excellent catalytic effect in the Fenton system, persulfate-based advanced oxidation processes, and electrocatalytic system. This review ends with a discussion of the challenges and future trends of the application of LDHs in wastewater treatment.
Journal Article
Vanadium(V) Removal from Aqueous Solutions and Real Wastewaters onto Anion Exchangers and Lewatit AF5
Adsorption abilities of weakly (Purolite A830), weakly basic/chelating (Purolite S984), and strongly basic (Lewatit MonoPlus SR7, Purolite A400TL, Dowex PSR2, Dowex PSR3) ion exchange resins of different functional groups and microporous Lewatit AF5 without functional groups towards vanadium(V) ions were studied in batch and column systems. In the batch system, the influence of the sorbent mass (0.01–0.1 g), pH (2–10), the phase contact time (1–1440 min),and the initial concentration (5–2000 mg/L) were studied, whereas in the column system, the initial concentrations (50, 100, and 200 mg/L) with the same bed volume and flow rate (0.4 mL/min) were studied. Desorption agents HCl and NaOH of 0.1–1 mol/L concentration were used for loaded sorbent regeneration. The pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models as well as the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were used to describe kinetic and equilibrium data to acquire improved knowledge on the adsorption mechanism. The desorption efficiency was the largest using 0.5 mol/L NaOH for all sorbents under discussion. Purolite S984, Purolite A830, and Purolite A400TL, especially Purolite S984, are characterized by the best removal ability towards vanadium(V) from both model and real wastewater.
Journal Article
Efficient Removal of Uranium (VI) by One-Step Synthetic Environmentally Friendly Hydroxyapatite Modified Attapulgite Composite Material: Adsorption Properties and Mechanism Studies
A one-step hydrothermal method was successfully employed to synthesize hydroxyapatite modified attapulgite composite material (HAP/ATP), which was characterized to determine physicochemical properties. Furthermore, the performance and mechanism of uranium removal by HAP/ATP were extensively investigated. Results indicated that HAP/ATP reached adsorption equilibrium for uranium at around 20 min with a maximum adsorption capacity of 387.27 mg·g
−1
. Modern characterization techniques identified ion exchange, complexation, dissolution–precipitation, and electrostatic adsorption as the primary mechanisms for uranium removal by HAP/ATP. ATP, a type of clay mineral, possesses a large specific surface area and natural pores. When utilized as a carrier, ATP reduced agglomeration of load materials. HAP can introduce more adsorption functional groups for attapulgite, this is a synergy, exerting the complementarity of materials. HAP/ATP demonstrates promising potential as an environmentally friendly adsorbent material for the treatment of radioactive uranium-containing wastewater.
Journal Article
Metal Recovery from Wastewater Using Electrodialysis Separation
Electrodialysis is classified as a membrane separation process in which ions are transferred through selective ion-exchange membranes from one solution to another using an electric field as the driving force. Electrodialysis is a mature technology in the field of brackish water desalination, but in recent decades the development of new membranes has made it possible to extend their application in the food, drug, and chemical process industries, including wastewater treatment. This work describes the state of the art in the use of electrodialysis (ED) for metal removal from water and wastewater. The fundamentals of the technique are introduced based on the working principle, operational features, and transport mechanisms of the membranes. An overview of the key factors (i.e., the membrane properties, the cell configuration, and the operational conditions) in the ED performance is presented. This review highlights the importance of studying the inter-relation of parameters affecting the transport mechanism to design and optimize metal recovery through ED. The conventional applications of ED for the desalination of brackish water and demineralization of industrial process water and wastewater are discussed to better understand the key role of this technology in the separation, concentration, and purification of aqueous effluents. The recovery and concentration of metals from industrial effluents are evaluated based on a review of the literature dealing with effluents from different sources. The most relevant results of these experimental studies highlight the key role of ED in the challenge of selective recovery of metals from aqueous effluents. This review addresses the potential application of ED not only for polluted water treatment but also as a promising tool for the recovery of critical metals to avoid natural resource depletion, promoting a circular economy.
Journal Article
Effluent Organic Matter (EfOM) in Wastewater: Constituents, Effects, and Treatment
Wastewater reuse is being increasingly emphasized as a strategy for conservation of limited resources of freshwater and as a mean of safeguarding the aquatic environment due to contaminants present in wastewater. Although secondary and tertiary treated wastewater is often discharged into surface waters, it cannot be reused without further treatment. One of the parameters of concern for human and environmental health is components of organic matter originating from wastewater treatment plant (WWTP) effluents. This effluent organic matter (EfOM) should be carefully characterized in order to find an optimum treatment method for water reuse. This review presents the components of EfOM present in WWTP effluents and various treatment methods that may be employed for reduction of EfOM. These processes include flocculation, adsorption, biofiltration, ion exchange, advanced oxidation process, and membrane technology. The removal efficiency is discussed in terms of removal of total organic carbon, endocrine-disrupting chemicals (EDCs), pharmaceuticals and personal care products (PPCPs), different polarity fractions (such as hydrophobic and hydrophilic), and molecular weight distribution of organic matter.
Journal Article
Hydrogeochemical Evaluation and Multivariate Statistical Analysis of Groundwater for Sustainable Groundwater Quality Management in the Industrial Corridor of Ranipet District, Tamil Nadu, India
Groundwater is gradually becoming the primary water source for humans and other living organisms to sustain life on Earth. The groundwater quality in the industrial regions has been significantly contaminated in recent years due to anthropogenic activities, leading to various human health issues. In this study, the groundwater quality and hydrogeochemical characteristics of the Ranipet Industrial Corridor (RIC) were assessed by employing multivariate statistics, standard scatter plots, and the water quality index (WQI). Forty groundwater samples (12 bore wells and 28 open wells) were collected during the post-monsoon (January 2022) season, and the estimation of physicochemical parameters was carried out based on American Public Health Association (APHA) guidelines. The evaporation and rock-water interaction are controlling groundwater hydrochemistry in the study area, as illustrated by Gibbs's diagram. In contrast, 82% of groundwater samples are severely affected by human activity, and 12% are impacted by silicate weathering, illustrated by scatter plots. According to the Chadha diagram, gypsum dissolution is the primary reason for the chemical composition of groundwater in the RIC (87.5%). The primary hydrochemical processes in the study area include silicate weathering, evaporation, ion exchange, and rock-water interaction. The Mukundarayapuram, Navlock, and Melvisharam region’s groundwater quality is unsuitable (92.5%) for irrigation due to the high concentration of sodium, based on Sodium Adsorption Ratio (SAR) results. Anthropogenic activities are the primary cause of groundwater degradation and hydrogeochemical changes, with the groundwater quality of RIC being over 60% very poor. A comprehensive treatment procedure before effluent discharge and stringent water regulating policies governed by environmental monitoring organizations are the pressing priorities to build a sustainable environment and reduce the health risks of groundwater.
Journal Article
Suitability of Electrodialysis with Monovalent Selective Anion-Exchange Membranes for Fractionation of Aqueous Mixture Containing Reactive Dye and Mineral Salt
To fulfil the goals of the circular economy, the treatment of textile wastewater should be focused on the recovery of valuable components. Monovalent anion-selective electrodialysis (MASED) was applied for the separation of reactive dyes from mineral salts. Standard cation-exchange membranes (CM membranes) and monovalent selective anion-exchange membranes (MVA membranes) were used in the electrodialysis (ED) stack. The separation efficiency was evaluated for model solutions of various reactive dyes (varying in molecular weight and chemical reactivity) containing NaCl. In the course of MASED, the mineral salt was successfully removed from the dye solutions with an efficacy of 97.4–99.4%, irrespectively of the composition of the treated solution. The transport of dye molecules through the ion-exchange membranes (IEMs) from diluate to concentrate compartments was irrelevant. Nonetheless, a significant adsorption of dye particles on the membranes was observed. Around 11–40% of the initial dye mass was deposited in the ED stack. Dye adsorption intensity was significantly affected by dye reactivity. This study showed the potential of the MASED process for the separation of the reactive dye from the mineral salt on condition that antifouling membrane properties are improved. The obtained streams (the concentrate rich in mineral salt and the diluate containing the reactive dye) can be reused in the dye-house textile operations; however, some loss of dye mass should be included.
Journal Article
The Sorption of Lead and Cadmium by Hydroxyapatite-Biochar Nanocomposite from Aqueous Solution
Lead (Pb) and cadmium (Cd)-contaminated wastewater treatment has become a major worldwide problem. The use of hydroxyapatite (HAP)-based composites may be an eco-friendly method for removing Pb and Cd from aqueous solutions. Based on the concept of treating waste with waste, we supported HAP particles on spent mushroom-substrate biochar (SMSBC), creating a new composite (HAP/BC) for removing Pb and Cd from solution. The sorption of Pb and Cd by HAP/BC was systematically studied in single and binary heavy metal systems. A series of characterization analyses were applied to investigate the properties of HAP/BC and explain the Pb and Cd removal mechanisms. The results revealed that the HAP content, reaction time, initial Pb and Cd concentrations, initial pH of the solution and competing cations affected Pb and Cd removal by HAP/BC. SMSBC effectively reduced HAP agglomeration, thereby resulting in HAP/BC with outstanding Pb and Cd removal capacities. The presence of Pb was not conducive to Cd removal, while the Pb removal efficiency was barely affected by the presence of Cd in the binary Pb–Cd system. Combining the results of the bath experiments with the characterization analyses, the reaction between HAP/BC and Pb might be primarily a dissolution–precipitation process, whereas the reaction with Cd was primarily an ion exchange. Additionally, oxygen-containing functional groups and cation-π interactions might also play a role in Pb and Cd sorption. Overall, the eco-friendly HAP/BC demonstrated significant potential for Pb and Cd decontamination and provided insights for the efficient use of SMS resources.
Highlights
SMSBC use as a carrier could clearly reduce the clustering effect of HAP particles.
HAP/BC exhibited superior Pb and Cd removal capacities in solution.
Dissolution–precipitation dominated the reaction process between HAP/BC and Pb.
The Cd removal process by HAP/BC was primarily controlled by ion exchange.
Journal Article