Heavy Metals In Wastewater Research Articles

Study on adsorption of hexavalent chromium by composite material prepared from iron-based solid wastes

A new adsorbent with chromium removal function was synthesized by carbon thermal method using iron-containing waste Fenton sludge and carbon-containing solid waste fly ash to treat high pH scoring wastewater generated from industrial processes. The results showed that the adsorbent used T = 273.15 K, pH = 10, t = 1200 min, C0 = 100 mg/L, had a removal rate of Cr(VI) of more than 80%, and the adsorption capacity could reach 393.79 mg/g. The characterization results show that the synthesized mesoporous nitrogen-doped composite material has a large specific surface area and mesoporous structure, and the surface of the material is rich in oxygen-containing functional groups and active sites. Compared with other studies, the adsorption capacity of the material is larger, which indicates that the removal effect of Cr(VI) in this study is better. The adsorption kinetic results show that the adsorption follows a pseudo second kinetic model, and the adsorption process is a chemisorption involving electron sharing or electron exchange. This experiment designed a simple method to synthesize mesoporous nitrogen-doped composites using industrial solid waste, with raw materials from cheap and easily available industrial solid waste, and solved the dual problems of heavy metals in wastewater and solid waste, providing a new idea for the resource utilization of Fenton sludge while not producing secondary pollution.

Photo-assisted self-driven bioelectrochemical systems for simultaneous enhanced treatment of etching terminal wastewater and selective recovery of heavy metals

Practical application of photo-assisted bioelectrochemical systems (BESs) for actual etching terminal wastewater (ETW) treatment, requires its energy-saving and high treatment efficiency with simultaneous recovery of multiple heavy metals. Herein photo-assisted self-driven BESs composed of two serially connected microbial fuel cells (MFC) in-situ utilized for powering one microbial electrolysis cell (MEC), are continuously fed with actual ETW. Such BESs achieve enhanced recalcitrant organics mineralization (37.9–38.2%) with simultaneous Cu(II) recovery (68.2 ± 0.4%-69.1 ± 0.4%) in the cathodes of MFCs, along with those (recalcitrant organics mineralization: 29.9 ± 0.4%; Ni(II) recovery: 64.9 ± 0.0% on the cathode electrodes; Zn(II) recovery: 75.7 ± 1.4% at the cathodic bottoms) in the MECs without any external energy consumption, allowing the final effluent meeting the China national wastewater discharge standards. Active species of ·OH, O2·-, holes and H2O2 varying degrees contribute to recalcitrant organics mineralization in the MFC and MEC units. This study provides an alternative zero energy consumption approach for efficient mineralization of recalcitrant organics with simultaneous selective recovery and separation of multiple heavy metals in actual ETW, moving photo-assisted self-driven BESs closer to applicable complex wastewater treatment with simultaneous recovery of multiple value-added heavy metals.

Recent progress in electrospun nanofibers and their applications in heavy metal wastewater treatment

Recent progress in electrospun nanofibers and their applications in heavy metal wastewater treatment

Assessment of heavy metals removal in a wastewater using aquatic ferns

Aquatic ferns, which due to their rapid growth on the surface of the water in aquatic areas in many countries as an invasive species threaten the aquatic life and ecosystem of the regions, have the ability to remove heavy metals in wastewater. In this study, their use in removal of existing heavy metals in a domestic wastewater was experimented and the results proved their remarkable efficiency in treating such a wastewater. This research was conducted in two steps; laboratory and semi-industrial. Applying a jar testing apparatus was the first attempt in laboratory scale and optimization of the following four different factors by a routine procedure was the further goal: pH-value, reaction time, absorbent, pollutant concentration. Afterwards, it was scaled up by a real wastewater and removal efficiency was evaluated under optimum conditions designed by the basic experiments. In the second stage, the reactor was designed and constructed on a semi-industrial scale and the removal rate of contaminated metals was achieved. Focusing on the energy efficiency after the heavy metal removal in this method in comparison with another method (active sludge) can be considered to be suggested for treating domestic wastewaters which include considerable contents of heavy metals.

Exploration of treatment technology for heavy metal wastewater

Among the current pollutants in our water bodies, the one that has the greatest degree of pollution and impact on the water environment is heavy metal wastewater. Various heavy metal ions in water bodies can seriously disrupt the ecological balance of water bodies and spread throughout the biosphere through the natural material cycle and other means. Excess heavy metal ions not only seriously endanger the health of aquatic organisms, but can also enrich in animals and even humans, posing a serious threat to human health and causing failure or damage to vital organs such as the human internal organs and brain. The common heavy metal ions in existing water bodies are Cu2+, Hg2+, Pb2+ etc. Due to their inherent difficulty in degradation, enrichment and persistence, heavy metal ions make heavy metal wastewater treatment different from other traditional pollutant treatment methods. This paper examines the two main techniques currently used to remove heavy metals from water bodies: physical, chemical and biological techniques, and summarises the advantages and disadvantages of both methods. It is proposed that future treatment methods for heavy metal wastewater should develop an environmentally friendly and efficient systematic approach based on biotechnology and synergistic multi-technologies.

Bioremediation of Heavy Metals in Wastewaters: A Concise Review

Bioremediation of Heavy Metals in Wastewaters: A Concise Review

Heavy Metal Removal from Aqueous Effluents by TiO2 and ZnO Nanomaterials

The presence of heavy metals in wastewater, such as Ni, Pb, Cd, V, Cr, and Cu, is a serious environmental problem. This kind of inorganic pollutant is not biodegradable for several years, and its harmful effect is cumulative. Recently, semiconductor nanomaterials based on metal oxides have gained interest due to their efficiency in the removal of heavy metals from contaminated water, by inducing photocatalytic ion reduction when they absorb light of the appropriate wavelength. The most commonly applied semiconductor oxides for these purposes are titanium oxide (TiO2), zinc oxide (ZnO), and binary nanomaterials composed of both types of oxides. The main purpose of this work is to critically analyse the existent literature concerning this topic focusing specially in the most important factors affecting the adsorption or photocatalytic capacities of this type of nanomaterials. In particular, photocatalytic activity is altered by various factors, such as proportion of polymorphs, synthesis method, surface area, concentration of defects and particle size, among others. After a survey of the actual literature, it was found that, although these metal oxides have low absorption capacity for visible light, it is possible to obtain an acceptable heavy metal reduction performance by sensitization with dyes, doping with metallic or nonmetallic atoms, introduction of defects, or the coupling of two or more semiconductors.

Sustainable decontamination of heavy metal in wastewater and soil with novel rectangular wave asymmetrical alternative current electrochemistry.

A new concept of removal and recovery of heavy metals and simultaneous regeneration and reuse of ethylenediamine-tetraacetic acid (EDTA) in soil washing effluent containing metal-EDTA complexes is proposed, which is used to remediate heavy metal contaminated soil. To achieve this goal, soil washing approach coupled with rectangular wave asymmetrical alternative current electrochemistry (RW-ACE) equipped with amidoxime-functionalized electrodes (Ami-CF) is employed. With high hydrophilicity and strong binding affinity, Ami-CF could specifically compete for heavy metals over EDTA under electric field. RW-ACE system is found successfully to achieve the non-destructive decomplexation of heavy metal-EDTA, and then regenerate EDTA for highly recycling, which saves as high as 98.9 % EDTA consumption compared with conventional washing method. Moreover, more than 90% of heavy metals are recovered and deposited on the electrode with a majority of them existed as zero-valence state as evidenced by XPS. The RW-ACE method is universal for various heavy metals such as Cu2+, Zn2+, Cd2+, and Pb2+ in an authentic contaminated soil, and the loss of soil nutrient is very limited. Along with long-term assessment and operation cost estimation, the RW-ACE method is a sustainable remediation approach for the heavy metal polluted wastewater and soils, and easily scaled up for field practice.

Characterization and Potential of Samanea saman-Activated Carbon on Adsorption of Copper from an Aqueous Solution

The mining and electroplating industries have resulted in the contamination of the environment with heavy metal. This has resulted in a serious threat to the ecological environment and human health due to the presence of copper pollution. To address this issue, extensive efforts have been made to develop effective methods for removing contaminants, particularly heavy metal, and Samanea saman (SS) was selected as precursor production of activated carbon. Therefore, this study is aimed at investigating Samanea saman-activated carbon (SSAC) to remove copper from an aqueous solution. SS was chemically activated by potassium carbonate and carbonized at 600°C for 5 hours, while SSAC was characterized by scanning electron microscopy-energy dispersive X-ray (SEM-EDS), Fourier-transform infrared (FTIR), and proximate tests. Copper adsorption on SSAC was evaluated by the Langmuir, Freundlich, Langmuir, Freundlich, Redlich-Peterson, Harkin-Jura, and Jovanovic models. Pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models were used to identify adsorption process mechanism. SEM-EDS results presented that the pore of SSAC was heterogeneous, irregular in shape, and mesopore. In addition, FTIR analysis identified the main functional groups present in SSAC as C-H, C-O-C, and C-O. The proximate test conducted on SSAC determined the water content, volatile matter, ash content, and fixed carbon to be 0.61%, 22.26%, 9.77%, and 67.97%, respectively. The results showed that SSAC exhibited exceptional performance with copper removal efficiency of 99.49% under an adsorbent mass of 0.25 g, a reaction time of 30 minutes, and a concentration of 10 mg/L. Isotherm adsorption of SSAC followed the Redlich-Peterson model with an adsorption capacity (Qm) of 0.663 mg/g, correlation value ([Formula: see text]) of 0.9992, and pseudo-second-order pattern [Formula: see text]. Therefore, SSAC can be proposed as a potential and economical biomaterial to treat heavy metal in wastewater.

Phytoremediation of selected heavy metals contaminated water by Amaranthus hybridus in hydroponic system

Contamination of heavy metals in wastewater is of growing concern not only for aquatic biodiversity but also for human health. Different physical and chemical methods have been traditionally utilized for the removal of these heavy metals. However, in the present study, the phytoremediation capacity of the Amaranthus hybridus (Indian cholai) plants was investigated using hydroponic technology. Instead of using the nutrient solution to meet plant growth requirements in hydroponic systems, partially treated wastewater can be directly fed to the roots of the plant. Plants were grown for 5 weeks in an artificial wastewater solution with Nickel (Ni), Iron (Fe), and Strontium (Sr) to estimate their removal rates from the . The plants exhibit removal rates of 99.86 %, 87.09 %, and 70.25 % for Ni, Fe, and Sr respectively. The polluting metals were shown to accumulate these heavy metals through roots and translocate them to the shoots and floral section. The bioconcentration factor for Nickel, Iron and Strontium was found to be 0.706, 0.68, and 1.08 respectively. The translocation factor was also calculated and was found to be 1.52, 1.77, and 4.34 respectively. The current investigation found that A. hybridus has the potential to be a Ni, Fe, and Sr hyperaccumulator.

Preparation of an enhanced chitosan modified flocculant with both chelation adsorption and flocculation effects for efficient treatment of Pb2+ heavy metal wastewater

Preparation of an enhanced chitosan modified flocculant with both chelation adsorption and flocculation effects for efficient treatment of Pb2+ heavy metal wastewater

Research on Novel Heavy Metal Wastewater Treatment Methods

Heavy metals are frequently present in industrial effluent, and their excess can be detrimental to human health. Therefore, industrial wastewater needs to be treated before it can be discharged. Key solutions for the treatment of heavy metal wastewater are analyzed and evaluated based on existing research, taking into account elements like removal effectiveness, cost, ease of recycling, and number of reuses. This paper introduces two conventional and three novel heavy metal removal technologies are presented. The fundamental ideas, ideal circumstances, benefits, and drawbacks of each technology are summarized, along with a prediction of future technical developments. Although nanosorbents and microbial fuel cells are very efficient, their expenses are expensive. Membrane technology has a wide range of potential applications and is a great choice for the removal of heavy metals when combined with other technologies. Future wastewater treatment for heavy metals has a bright future thanks to all of these technologies.

Effect of different pore membrane on ultrafiltration treatment of wastewater contained heavy metals complexed by palygorskite

The treating effects of four hollow fiber membranes on heavy metals complexed by palygorskite in wastewater by complexation–ultrafiltration were investigated. The membranes contained three asymmetric polysulfone membranes and a polyethersulfone membrane with nominal molecular weight cut-off (MWCO) between 6,000 and 100,000 Da. The results through the comprehensive analysis of the rejection rate and the flux of normalized membranes showed that 6,000; 10,000 and 6,000 Da ultrafiltration membranes were suitable for the ultrafiltration of Cu2+, Zn2+, Cd2+, respectively. The pseudo-first-order reaction rate equation can better represent the reaction behavior of the complexes of favorite-ultraviolet at four membrane pore sizes. Four kinds of ultrafiltration membranes with molecular weight cut-offs of 6, 10, 50, and 100 kDa were fouled with wastewater containing Cu2+, Zn2+, Cd2+ complexed by palygorskite in complexation–ultrafiltration process at a transmembrane pressure of 1 bar and 20°C. The influence of molecular weight cutoff was investigated. The permeation flux decreased with time. Permeate flux declined with time gradually and finally stabilized after about 140 min of operation for all the membranes tested. 50,000 Da membrane showed the highest flux decline. The concentration of heavy metals and types of materials affect the distribution of resistance. The highest proportion of resistance for 6,000 and 10,000 Da membranes is the resistance of the membrane. For 50,000 and 100,000 Da membranes, the highest proportion of its resistance is the filter cake layer resistance. The results provide a kind of inorganic clay complexing agent in large reserves for the complexation–ultrafiltration of heavy metal wastewater.

Investigation of a two-dimensional model on Cu2+ recovery in bioemectrochemical system

A novel microbial fuel cell (MFC) was designed to recover Cu2+ from simulated electroplating wastewater. The BES has two chambers separated by a bipolar membrane and two cathodes. To explore the rate controlling step affecting Cu2+ deposition rate, spatial mass distribution and its deposition process during Cu2+ deposition on MFC cathode. A two-dimensional, transient model was built to study the factors that limiting Cu2+ deposition in MFC. We found that the formation of ion scarcity zone would decrease Cu2+ deposition rate, which leading to mass transfer limiting Cu2+ reduction on cathode surface (x=0 m). While near the cathode tip (x=0.02 m), the highest deposition rate and thickness was obtained. Furthermore, diffusion and electro-migration of Cu2+ were synergistic to improve Cu2+ reduction efficiency, and electro-migration of Cu2+ had a great impact on Cu2+ transferring from electrolyte domain to electrode surface. This research provided a new studying direction for heavy metal wastewater treatment and metal separation and recovery in the electroplating industry to improve metal ions deposition rate.

Crosslinked polymer nanocomposites for wastewater heavy metal adsorption: A review

Crosslinked polymer nanocomposites for wastewater heavy metal adsorption: A review

Double-charged self-assembled rGO/g-C3N4 membrane prepared by “functional group substitution” for heavy metal ions rejection at low pressure

Heavy metals are still the critical pollutants in industrial wastewater and there is an urgent need for efficient and environmentally friendly treatment technologies. Reduced graphene oxide (rGO) is widely used for preparations of nanofiltration (NF) membranes but suffers from poor hydrophilicity and electronegativity. In this work, a double-charged rGO/g-C3N4-P membrane was prepared for removal of heavy metals at low pressure. Graphitic carbon nitride (g-C3N4) assisted reduction of GO membranes under ultraviolet (UV) irradiation, and the modification of functional groups with high polarity improved the hydrophilicity of membrane surface. The filtration performance for heavy metals of rGO/g-C3N4-P membrane was evaluated under low pressure (1–2 bar). The rejection rates of Cu2+, Cr3+, Mn2+, Cd2+, and Pb2+ by membranes reduced by UV for 18 h (rGO/g-C3N4–18-P membrane) reached 94.72 %, 98.05 %, 82.32 %, 88.2 % and 77.15 %, respectively. In the experiment of mixed simulated wastewater, the rejection rates of NO3− and SO42− both reached >95 %. Outstanding rejection rates were attributed to the interaction and the synergy effect of double-charged layers as well as steric effects. Meanwhile, the water flux of rGO/g-C3N4–18-P membrane was as high as 37.14–50.16 L m−2h−1bar−1 (1–2 bar). The high flux was due to the reduced degree of oxidation so that water molecules transported between GO nanochannels more smoothly and the transport path was shortened through the nanopores of g-C3N4. Obviously, flux and heavy metal rejection of rGO/g-C3N4–18-P membrane were simultaneously improved, breaking “trade-off” effect. Furthermore, rGO/g-C3N4–18-P membrane showed excellent antifouling ability and the potential for heavy metal wastewater filtration in comparison with other NF membranes reported in literature.

The electron transport mechanism of downflow Leersia hexandra Swartz constructed wetland-microbial fuel cell when used to treat Cr(VI) and p-chlorophenol.

Constructed wetland-microbial fuel cells are used to treat heavy metal and/or refractory organic wastewater. However, the electron transport mechanism of downflow Leersia hexandra constructed wetland-microbial fuel cells (DLCW-MFCs) is poorly understood when used to treat composite-polluted wastewater containing Cr(VI) and p-chlorophenol (4-CP) (C&P). In this study, metagenomics and in situ electrochemical techniques were used to investigate the electrochemical properties and the electricigens and their dominant gene functions. The DLCW-MFC was used to treat C&P and single-pollutant wastewater containing Cr(VI) (SC) and 4-CP (SP). The results showed that C&P had a higher current response and charge transfer capability and lower solution resistance plus charge transfer resistance. The anode bacteria solution of C&P contained more electron carriers (RF, FMN, FAD, CoQ10, and Cyt c). Metagenomic sequencing indicated that the total relative abundance of the microorganisms associated with electricity production (Desulfovibrio, Pseudomonas, Azospirillum, Nocardia, Microbacterium, Delftia, Geobacter, Acinetobacter, Bacillus, and Clostridium) was the highest in C&P (4.24%). However, Microbacterium was abundant in SP (0.12%), which exerted antagonistic effects on other electricigens. Among the 10 electricigens based on gene annotation, C&P had a higher overall relative abundance of the Unigene gene annotated to the KO pathway and CAZy level B compared with SC and SP, which were 1.31% and 0.582% respectively. Unigene153954 (ccmC), Unigene357497 (coxB), and Unigene1033667 (ubiG) were related to the electron carrier Cyt c, electron transfer, and CoQ biosynthesis, respectively. These were annotated to Desulfovibrio, Delftia, and Pseudomonas, respectively. Unigene161312 (AA1) used phenols and other substrates as electron donors and was annotated to Pseudomonas. Other functional carbohydrate enzyme genes (e.g., GT2, GT4, and GH31) used carbohydrates as donors and were annotated to other electricigens. This study provides a theoretical basis for electron transfer to promote the development of CW-MFCs.

Aminoimidazole ionic liquid (IL) embellishment of nanofiltration (NF) membrane to simultaneously enhance heavy metals rejection and permeability

Most commercial nanofiltration (NF) membranes carry negative charges, which is unfavorable for rejecting positively charged impurities according to the Donnan effect. Two ionic liquids (ILs) with the same cation, namely 1-aminopropylimidazolium hexafluorophosphate ([C3NH2MIm]PF6) and 1-aminopropyl-3-methylimidazolium bromide ([C3NH2MIm]Br), were employed to improve membrane surface charge by surface modification. With the ILs regulating the membrane structure, the resultant membranes (IL-PA) displayed a rough surface with higher hydrophilicity, larger pores, enhanced surface charge and structure stability than the blank PA membrane. Specifically, with IL concentration increasing, the [C3NH2MIm]PF6 modified (PF6/PA) membranes showed enhanced isoelectric point (IEP) from 4.5 to 6.5, while that of the Br/PA membranes was decreased from 3.7 to 3.1. It indicates the anionic part of ILs determined its distribution in the PA layer. High Po/w of [C3NH2MIm]PF6 enabled high diffusivity in the PA layer, and thus, more [C3NH2MIm]+ grafted on the membrane surface, leading to high IEP and contact angle. Overall, the optimized 0.5PF6/PA membrane exhibited a high pure water flux of 62.2 L·m−2·h−1 and enhanced heavy metal removal efficiency (Cu2+ 97.1 %, Ni2+ 94.6 %, Cd2+ 95.5 %, Zn2+ 96.4 %). This work demonstrates the feasibility of specific functionalized ILs in heavy metal wastewater treatment.

Electrostatic self-assembly of nanoscale FeS onto MXenes with enhanced reductive immobilization capability for U(VI) and Cr(VI)

Herein, a MXenes decorated nanoscale FeS composites were developed via electrostatic self-assembly strategy to achieve efficient U(VI)/Cr(VI) adsorption-reduction. Different analytical techniques were applied to adequately characterize all as-prepared materials to determine the formation of species with the desired morphology and properties. Results revealed that the special chemical structure of MXenes could improve the dispersion of FeS nano-particles and suppress its aggregation. Meanwhile, the adsorption data closely well tailored with the Langmuir isotherm and Pseudo-second-order equation, and the maximum removal efficiencies were 88.5 and 107.2 mg/g for uranium(VI) and chromium(VI). It was also found that the presence of other cations and anions had no obvious influence on removal of U(VI)/Cr(VI), whereas the elimination process was a spontaneous endothermic reaction. More importantly, according to the spectroscopic analysis and DFT calculation, both FeS and surface functional groups on Ti3C2@FeS-PDA/PEI exhibited strong chemical affinities to the targeted pollutants, while FeS could effectively reduce Uranium(VI) to Uranium(IV) and Chromium(VI) to Chromium(III). This work facilitated the omnidirectional improvement of MXenes-based materials for the de-pollution of practical radionuclide or heavy metals wastewater.

Geopolymer composite spheres derived from graphene-modified fly ash/slag: Facile synthesis and removal of lead ions in wastewater

Geopolymer composite spheres derived from potassium-activated graphene-modified slag/fly ash powder were produced in a polyethylene glycol (PEG 400) solvent. The effect of graphene type (graphene oxide (GO) and few-layered graphene (GNP)) on the pore structure and lead ions (Pb2+) removal performance of the spheres were evaluated. The results showed that the composite spheres modified with GOs (0.1–0.4 wt%) and GNPs (1–4 wt%) could be spheroidized with an improved performance to adsorb Pb2+ in solution. The graphene-containing spheres reached a maximum BET surface area of 68.85 m2/g. Pseudo-second-order and Langmuir isotherm models could express the adsorption process, which was controlled by both monolayer adsorption and chemisorption. The obtained spheres also showed high adsorption capacities for Ni2+, Cu2+, Zn2+ and Cd2+ ions. Chemical, physical, electrostatic, ion exchange and cation-π interaction were attributed to the adsorption mechanism of the spheres. The spheres showed good cycling ability compared to those without graphene, which had potential application in heavy metal wastewater treatment.