Recovery Of Heavy Metals Research Articles

Hydrometallurgical recovery of critical metals from an incinerated fly ash of municipal solid waste from western India

ABSTRACT The global generation of 2.2 billion tons of municipal solid waste (MSW) as a result of population growth, rapid urbanization, and industrial development has highlighted an urgent need for MSW management. Incineration is widely accepted as one alternative to landfilling; however, the recovery of heavy metals from the incinerated fly ash (IFA) before its final disposal is highly desirable to make the process sustainable. In this study, we studied the recovery of zinc and lead from typical MSW-IFA employing hydrometallurgical techniques. Sulfuric acid leaching was performed to selectively leach out zinc over the lead at the optimal condition of H2SO4 concentration = 1.5 M, temperature = 30°C, S/L ratio = 150 g/L, time = 2 h, and stirring speed = 300 rpm. The sulfate leach liquor was treated with a 5% stoichiometric excess of oxalic acid to precipitate>99% of zinc to be recovered as ZnC2O4·2 H2O. Further, the remaining lead in leach residue was subsequently leached in 50 g/L NaCl solution for 2 h yielded>94% efficiency. The dissolved lead was crystallized to recover the crystals of PbCl2. The demonstrated process leads towards the recovery of critical metals from an alternative source of MSW-IFA.

Reusable granulated silica pillared clay for wastewater treatment, selective for adsorption of Ni(II)

The article presents a study on the suitability of silica pillared clay (SPC) encapsulated with biopolymers, such as alginate, chitosan, or a combination of both, for the adsorption of Ni(II) from aqueous solutions. In the current age of stringent environmental regulations, there is an urgent requirement to identify novel sorbents that can be readily commercialized and employed in large-scale systems to efficiently remove and recover metal compounds from wastewater. Therefore, the study aimed to encapsulate powdered silica pillared clay to produce stable granules via a modified solution casting method, which was confirmed through various characterization studies (FESEM, XRF, XRD, BET, and FTIR). The study found that ALG-SPC showed the best adsorption capacity, owing to its relatively high specific surface area and the negative charge of the alginate. In contrast, encapsulation with chitosan resulted in poor performance due to a significant reduction in porosity. The study also investigated the behaviour of ALG-SPC in a binary solution containing both Ni(II) and Cr(VI) and found that it exhibited selectivity for Ni(II) over Cr(VI). The presence of Cr(VI) did not negatively affect Ni(II) adsorption; in contrast, Ni(II) helped to Cr(VI) adsorption under a limited pH range. The study also conducted adsorption mechanism, kinetic, and equilibrium modelling. Recovery of adsorbed Ni(II) from saturated ALG-SPC was most effective in acidic solutions in comparison with electrolyte solution and methanol. The study's findings have important implications for the development of effective and selective adsorbents for heavy metal removal and recovery from wastewater.

Stepwise recovery of Ni, Cu, Zn, and Cr: A green route to resourceful disposal of electroplating sludge

The recovery of heavy metals from electroplating sludge not only reduces environmental damage, but also avoids the wastage of resources. However, acid leaching of electroplating sludge requires lengthy procedures for purification and separation of metals, which leads to high material consumption. In this study, alkali-leaching dealumination and a two-stage roasting water leaching process were combined to selectively recover Ni, Cu, Zn, and Cr from electroplating sludge. Thermodynamic calculations were used for analyzing the theoretical feasibility of roasting electroplating sludge and determining the factors affecting the recovery of Ni, Cu, Zn, and Cr in the roasting process. First, approximately 100 % Al was recovered as AlO2- after 6 mol/L of NaOH solution was treated at 90 ℃ for 1 h. Second, dealumination residue was mixed with NaOH and roasted at 800 ℃ for 1 h after water leaching, and nearly 99 % Cr was extracted as CrO42-. Third, more than 99 % Ni, Cu, and Zn were extracted as chlorine salts by blending NH4Cl into the dechroming residue and conducting roasting at 400 ℃ for 1 h after water leaching. Overall, this study provides a novel, simple, and efficient approach for the selective recovery of Ni, Cu, Zn, and Cr from electroplating sludge.

Investigations into the closed-loop hydrometallurgical process for heavy metals removal and recovery from biosolids via mild acid pre-treatment

Biosolids contain heavy metals (HMs), restricting their beneficial reuse in agricultural land. However, these metals can be a valuable resource in many applications if recovered efficiently. Therefore, the removal and recovery of HMs and other limiting contaminants in biosolids without degrading the organic nutrients of the resulting treated biosolids demands holistic investigations. A closed-loop hydrometallurgical treatment process for metal removal and recovery from biosolids was developed in this study. Firstly, mild acid treatment using 3% v/v H2SO4 at 25 °C, 600 rpm for 30 min was performed in a 1 L continuous stirred tank reactor to extract common HMs (such as As, Cd, Co, Cr, Cu, Ni, Pb, and Zn) from biosolids into the aqueous phase. The effects of solids concentration and acid types on the HMs extraction efficiency were studied. Then, the primary acid leachate stream was continuously recycled for metal extraction from biosolids until the dissolved metals in the solution reached saturation concentration. After that, the dissolved metals were recovered in staged NaOH precipitation and adsorption. Low solids contents (<5% w/v) using mineral acids having pH <2 and oxidation-reduction potential (ORP) ∼500 mV (versus SHE) favoured HMs solubilisation from biosolids with an average extraction efficiency of 70%. The dissolution of ferric iron (Fe3+) by H2SO4 and subsequent in-situ formation of ferric sulfate enhanced the metal extraction strength of the spent leachate stream during recycling. However, the solids loading in each leaching process must be kept low to prevent ferric concentration build-up and precipitation as the leachate pH steadily increases above 2 during recycling. Amongst the metal recovery methods investigated, H2O2 oxidation prior to 2-stage NaOH precipitation had the highest efficiency with 75–95% HMs recovery. The clarified stream was used to neutralise the acidic treated biosolids to close the process loop. The complete process flowsheet was developed with mass balances, and the fate of nutrients (mainly C, N, and P) and major per- and polyfluoro alkyl substances (PFAS) were overviewed.

Shoot-root signal circuit: Phytoremediation of heavy metal contaminated soil.

High concentrations of heavy metals in the environment will cause serious harm to ecosystems and human health. It is urgent to develop effective methods to control soil heavy metal pollution. Phytoremediation has advantages and potential for soil heavy metal pollution control. However, the current hyperaccumulators have the disadvantages of poor environmental adaptability, single enrichment species and small biomass. Based on the concept of modularity, synthetic biology makes it possible to design a wide range of organisms. In this paper, a comprehensive strategy of "microbial biosensor detection - phytoremediation - heavy metal recovery" for soil heavy metal pollution control was proposed, and the required steps were modified by using synthetic biology methods. This paper summarizes the new experimental methods that promote the discovery of synthetic biological elements and the construction of circuits, and combs the methods of producing transgenic plants to facilitate the transformation of constructed synthetic biological vectors. Finally, the problems that should be paid more attention to in the remediation of soil heavy metal pollution based on synthetic biology were discussed.

Heterotrophic anodic denitrification coupled with cathodic metals recovery from on-site smelting wastewater with a bioelectrochemical system inoculated with mixed Castellaniella species

Although Castellaniella species are crucial for denitrification, there is no report on their capacity to carry out denitrification and anode respiration simultaneously in a bioelectrochemical system (BES). Herein, the ability of a mixed inoculum of electricigenic Castellaniella species to perform simultaneous denitrification and anode respiration coupled with cathodic metals recovery was investigated in a BES. Results showed that 500 mg/L NO3−-N significantly decreased power generation, whereas 100 and 250 mg/L NO3−-N had a lesser impact. The single-chamber MFCs (SCMFCs) fed with 100 and 250 mg/L NO3−-N concentrations achieved a removal efficiency higher than 90% in all cycles. In contrast, the removal efficiency in the SCMFCs declined dramatically at 500 mg/L NO3−-N, which might be attributable to decreased microbial viability as revealed by SEM and CLSM. EPS protein content and enzymatic activities of the biofilms decreased significantly at this concentration. Cyclic voltammetry results revealed that the 500 mg/L NO3−-N concentration decreased the redox activities of anodic biofilms, while electrochemical impedance spectroscopy showed that the internal resistance of the SCMFCs at this concentration increased significantly. In addition, BES inoculated with the Castellaniella species was able to simultaneously perform heterotrophic anodic denitrification and cathodic metals recovery from real wastewater. The BES attained Cu2+, Hg2+, Pb2+, and Zn2+ removal efficiencies of 99.86 ± 0.10%, 99.98 ± 0.014%, 99.98 ± 0.01%, and 99.17 ± 0.30%, respectively, from the real wastewater. Cu2+ was bio-electrochemically reduced to Cu0 and Cu2O, whereas Hg0 and HgO constituted the Hg species recovered via bioelectrochemical reduction and chemical deposition, respectively. Furthermore, Pb2+ and Zn2+ were bio-electrochemically reduced to Pb0 and Zn0, respectively. Over 89% of NO3−-N was removed from the BES anolyte during the recovery of the metals. This research reveals promising denitrifying exoelectrogens for enhanced power generation, NO3−-N removal, and heavy metals recovery in BES.

Sulfur disproportionation realizes an organic-free sulfidogenic process for sustainable treatment of acid mine drainage

Biological sulfidogenic processes (BSPs) have been considered effective biotechnologies for the treatment of organic-deficit acid mine drainage (AMD) and heavy metal recovery. However, high-rate sulfide production relies on the continuous addition of exogenous organic substrates as electron donors to facilitate dissimilatory sulfate reduction, which substantially increases the operational cost and CO2 emission and also limits the wide application of BSPs in AMD treatment. In this study, we proposed a novel chemoautotrophic elemental sulfur disproportionation (SD) process as an alternative to conventional BSPs for treating AMD, in which sulfur-disproportionating bacteria (SDB) disproportionates sulfur to sulfide and sulfate without organic substrate supplementation. During the 393-day lab-scale test, we observed that the sulfur-disproportionating reactor (SDR) achieved a stable high-rate sulfide production, with a maximal rate of 21.10 mg S/L-h at an organic-substrate-free condition. This high rate of sulfide production suggested that the SD process could provide sufficient sulfide to precipitate metal ions from AMD. Thermodynamics analysis and batch tests further revealed that alkalinity rather than sulfate was the critical factor influencing the SD process, suggesting that the abundant sulfate present in AMD would not inhibit the SD process. The critical condition of SD in the SDR was therefore determined. Microbial community analysis showed that Dissulfurimicrobium sp. was the dominant SDB during the long-term operation regardless of dynamic sulfate and/or alkalinity concentrations, which provides evidence that SDB can be employed for sustainable and high-rate sulfide production for engineering purposes. A multi-stage AMD treatment system equipped with a SDR removed over 99% of the influent metals (i.e., Fe, Al, Zn, Cu, Pb) from AMD except for Mn. This study demonstrated that the novel SD process is a green and promising biotechnology for the sustainable treatment of organic-deficient metal-laden wastewater, such as AMD.

Physical, Static, and Kinetic Analysis of the Electrochemical Deposition Process for the Recovery of Heavy Metal from Industrial Wastewater.

Through the electrodeposition technique, toxic metals in wastewater can be removed and deposited on a chosen substrate with excellent selectivity. In this work, we use this technique to extract lead cations from simulated wastewater by using fluorine-doped tin oxide (FTO) substrate at various temperatures. In situ tracking of lead nucleation at advanced stages has been achieved by chronoamperometry. According to the experimental results, the theoretical models developed to study the kinetic growth of lead deposits in 2D and 3D are in good agreement. Nucleation rate and growth rate constants, for example, were found to be strongly influenced by temperature. Cottrell's equation is used to calculate the diffusion coefficient. X-ray diffraction, scanning electron microscopy, and energy-dispersiveX-ray techniques were used to investigate and characterize the lead deposits. The reported results could provide insight into the optimization of electrodeposition processes for heavy metal recovery from wastewater and electronic wastes.

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.

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.

Mycoremediation: Role of Mushroom in the bioremediation of heavy metals

The removal and recovery of heavy metals from the polluted environment are now possible because of the new and promising method known as bioremediation. Macrofungi can accumulate and break down a wide variety of hazardous metals and the same is a highly effective way to restore a damaged environment. In general, mushrooms recover contaminated or polluted soils using three efficient strategies: biodegradation, bioconversion, and biosorption. The process of mycoremediation employs a variety of wild and domesticated mushroom species which may break down significant amounts of organic and inorganic contaminants and eventually produce marketable goods or chemicals. White rot fungi have been widely employed in the conversion of pesticides, breakdown of petroleum hydrocarbons, and treatment of lignocellulosic waste in the pulp and paper sector. Several mushrooms, including Phanerochaete chrysosporium, Agaricus bisporus, Trametes versicolor, and Pleurotus ostreatus, among others, have been documented for their involvement in the remediation of contaminated locations..

Synthesis of graphene oxide grafted by diazanyl groups and its application in recovery of lead from lead-acid wastewater.

Heavy metal ion (HMI) in wastewater is a kind of resource that is wrongly placed. Recovery of heavy metal from lead-acid wastewater desires efficient and reusable functional materials. In this paper, graphene oxide-like with diazanyl groups (GOLA) was synthesized by a nucleophilic substitution reaction of graphene oxide-like with hydroxyl groups (GOLH) with diazane. GOLA exhibited good stability and recyclability in wastewater. The maximal adsorption capacity (qmax) values of GOLA for Pb(II), Cd(II), Cu(II), Ni(II), and Cr(III) ions were 505.80, 401.99, 83.48, 82.29, and 147.77mg/g, respectively. The equilibrium time of GOLA adsorbing HMIs was 20min. GOLA was employed to recover lead ions from lead-acid wastewater to give Pb(OH)2 and reusable water. Therefore, this paper provides a useful method of recycling lead from lead-acid wastewater.

Determination of elemental impurities in valproic acid an epilepsy drug by using ICP-MS

BackgroundAccording to previously published research, different analytical methods (GC, HPLC, etc.) were used to determine Valproic acid and its Genotoxic impurities. The heavy metals were also attempted to be determined using the ICP-MS technique in other drug substances. MethodsThe present work evaluated the 10 elemental impurities (Cd, Pb, As, Hg, Co, V, Ni, Fe, Al, and Sn) in Valproic acid by ICP-MS method utilising a microwave-assisted acid digestion process as there is no analytical method for the heavy metal analysis in Valproic acid. ResultsThe developed analytical method was selective, sensitive and rapid for capable of detecting heavy metal at 0.19 ppm As, 0.38ppm Hg, 0.06 ppm Pb, 0.06ppm Cd, 0.63 ppm Co, 1.25ppm V,2.5 ppm Ni, 25 ppm Fe, 25 ppm Al and 75 ppm Sn and further quantified from 0.375ppm As,0.75ppm Hg, 0.125 ppm Pb, 0.125ppm Cd, 1.25ppm Co, 2.5ppm V, 5 ppm Ni, 50 ppm Fe, 50ppm Al and 150 ppm Sn to 200 percent of limit concentration. The analytical method found to be linear with correlation coefficient > 0.99. The percentage recoveries of heavy metals at three different concentrations with spiking in samples of Valproic acid were achieved an acceptable range at 70% to 150 %. The method was precise and robust and its relative standard deviation was below 20%. The actual % RSD in precision are 1.0 % As, 0.5 % Hg, 0.5 % Pb, 1.2 % Cd,0.6 % Co, 0.6 % V, 0.6 % Ni, 0.5% Fe, 0.9 % Al and 0.3 % Sn. ConclusionHeavy metal analysis by ICP-MS is a powerful technique, Therefore the developed method can use for routine quantitative determination of 10 elemental impurities in Valproic Acid.

Biowaste Valorization to Produce Advance Carbon Material-Hydrochar for Potential Application of Cr (VI) and Cd (II) Adsorption in Wastewater: A Review

The dramatic increase in the use of biomass waste has caused a serious environmental pollution phenomenon. Biowaste valorization to produce advanced material-hydrochar is regarded as a promising carbon neutrality technology for biomass waste recycling and utilization. Hydrochar obtained by hydrothermal carbonization has attracted much attention due to its regular morphology, good physical and chemical stability, and abundant oxygen-containing functional groups on the surface. This reviews the preparation of hydrochar and the basic methods of modified hydrochar and expounds on the related reaction mechanism of adsorption. The adsorption and recovery of heavy metals, Cr (VI) and Cd (II), in wastewater by hydrochar were focused on. The experimental conditions of hydrochar, such as synthesis temperature, synthesis time, modified condition, adsorption capacity, adsorption isotherm, and adsorption kinetics, were compared. The adsorption conditions of hydrochar for Cr (VI) and Cd (II) in wastewater, including the adsorption pH value, the adsorption time, the adsorption temperature, and so on, have been summarized. The review develops a better understanding of Cr (VI) and Cd (II) adsorption by hydrochar in wastewater, making an innovative perspective for the improvement and large-scale application of hydrochar as an advanced carbon material as well as biowaste utilization.

Research Progress on Process-Intensified Water Treatment Applications

Process intensification (PI) is aimed towards essentially smaller, cleaner, safer, energy-efficient sustainable technologies involving the application of a number of strategies, including reducing the number of devices, miniaturization, process integration, improving mass and heat transfer, novel energy and separation techniques and combined optimization and control methodologies. Over the recent years, PI has attracted attention in the domain of aqueous medium adsorptive separations and wastewater treatment as well. Thus far, a limited number of investigations have appeared in the literature; in addition, there is yet a lack of published methods to follow the intensified solutions for processes in wastewater treatment. In this connection, this article aims to present an overview of the recent applications and advances in process-intensified decolorization of dyes; removal of aromatic hydrocarbons from wastewaters; and recovery of proteins, heavy metals and rare earth elements from aqueous media. Selected applications have been identified in terms of the PI techniques, and the corresponding process improvements have been discussed for a variety of examples with the aim of contributing to the future progress of applications. It has been confirmed that considerable process improvements could be possible, such as intensified process efficiency, improved adsorption and separation performance, and minimized sorbent requirement and processing time. Even though there have been considerable developments in the field, there is still a need for further developments for the enhancement of the technologies in adsorption wastewater treatment using a systems approach.

Development of a magnetic calcium-alginate hydrogel-sphere encapsulated with Fe–Mn–Zr ternary metal composite for heavy metal adsorption

Heavy metal contamination has become one of the greatest global environmental problems. In this study, a magnetic calcium-alginate hydrogel-sphere encapsulated with Fe–Mn–Zr ternary-metal composite (MCHETC) was prepared through a combined co-precipitation and extrusion approach and used for the adsorption of heavy metals in aqueous solutions. The active sites were dispersed in the MCHETC, which can be separated by the magnetic force for the ease in operation. Above 80% of ultimate adsorption was completed at a contact time of 5 h. The copper uptake history was well described by the intraparticle surface diffusion model, suggesting a multi-step process for the adsorption. The optimum pH for adsorption was 4; the maximum adsorption capacity was 103.1 mg-Cu/g. The adsorption capability well remained after the 5 adsorption–desorption cycles and the copper could be recovered. Furthermore, the adsorbent performed well in the nature water spiked with copper ions. The mechanism studies illustrated that the adsorption was mainly controlled by the ion-exchange reaction. This study demonstrated that the MCHETC adsorption technology may be used for heavy metal removal and recovery with higher efficacy.

MoS42- intercalated magnetic layered double hydroxides for effective removal and expedient recovery of heavy metals from soil

Mg-Al layered double hydroxides with MoS42- intercalated and magnetic modification by Fe3O4 (M−MoS4−LDH) was synthesized by one-pot method for capturing and separating heavy metals (Cu2+/Pb2+/Zn2+/Ni2+) from soil. The intercalation of MoS42- considerably improved the removal efficiency of heavy metals, and magnetic materials facilitated the separation of heavy metals from the soil to overcome the potential risk of the absorbed heavy metals. Removal kinetics of heavy metals were found to better follow the intraparticle diffusion model and pseudo-second-order kinetic model. The adsorption results of Cu2+ and Pb2+ were better described by the Freundlich isotherm, and Langmuir isotherm model well fitted the Zn2+ and Ni2+ adsorption data. Additionally, adsorption mechanism of M−MoS4−LDH for Cu2+/Pb2+/Zn2+/Ni2+ with different concentrations was also be explored. As the concentration of Cu2+/Pb2+/Zn2+/Ni2+ in soil was small, MoS42- preferentially combined with heavy metals, and heavy metals were immobilized in the interlayer of LDHs layer. With the increase of heavy metals, the precipitation for Cu2+/Pb2+ and the isomorphic substitution for Zn2+/Ni2+ were investigated and proposed. The co-existing ions experiments demonstrated that M−MoS4−LDH has high selective adsorption efficiency for heavy metals, column leaching experiments indicated that the heavy metals eventually immobilized by M−MoS4−LDH and prevented further migration in soil. Regeneration and recovery experiments suggested that M−MoS4−LDH could be reused for several time with high-efficiency and avoiding secondary contamination. This work provided an excellent removal and convenient recovery strategy for the treatment of heavy metal contaminated soil.

Preparation of copper-based catalysts from electroplating sludge by ultrasound treatment and their antibiotic degradation performance

The recovery of heavy metals from electroplating sludge is important for alleviating heavy metal pollution and recycling metal resources. However, the selective recovery of metal resources is limited by the complexity of electroplating sludge. Herein, CuFe bimetallic Fenton-like catalysts were successfully prepared from electroplating sludge by a facile room-temperature ultrasonic-assisted co-precipitation method. The prepared CuFe–S mainly consisted of nanorods with diameters of 20–30 nm and lengths of 100–200 nm and a small number of irregular particles. Subsequently, we performed tetracycline (TC) degradation experiments, and the results showed that the product CuFe–S had very good performance over a wide pH range (2–11). At an initial pH = 2, CuFe–S could degrade 91.9% of 50 mg L−1 TC aqueous solution within 30 min, which is better than that of a single metal catalyst. Free radical scavenging experiments and electron paramagnetic resonance (EPR) tests revealed that ·OH was the main active species for the degradation of TC by CuFe–S. In conclusion, a CuFe bimetallic Fenton-like catalyst was developed for the catalytic degradation of antibiotics, which provides a novel technical route for the resource utilization of electroplating sludge and shows an important practical application prospect.

EFFECT OF ULTRASOUND ON EXTRACTION OF HEAVY METALS FROM SEWAGE SLUDGE IN THE CONTEXT OF A POTENTIAL ECOLOGICAL RISK ASSESSMENT

The aim of the research was to investigate the effect of ultrasound waves on the recovery of heavy metals (HMs) from sewage sludge. For this purpose, we conducted a three-step sequential extraction process proposed by the Community Bureau of Reference (BCR; presently the Standards, Measurements and Testing Programme). In the experiment use was made of certified reference material ERM-CC144 SEWAGE SLUDGE (Joint Research Centre; JRC). The content of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in certified material was determined by atomic absorption spectrometry using the Avio 200 ICP-OES apparatus (PerkinElmer Inc.). To reduce the sequential extraction time, ultrasound treatment was used instead of long hours of shaking. Sonication was conducted in an ultrasonic bath (Sonic-5; Polsonic). The sonication time was set at 20, 40 and 70 minutes. The frequency, power and temperature during the ultrasound treatment were kept constant. The recovery values of heavy metals obtained by the modified sequential extraction method were at similar levels to those achieved by the conventional one. Moreover, it has also been shown that after only 20 minutes of sonication, the recovery values can be obtained similarly as for the conventional method. In order to check whether the ultrasound waves have a significant impact on the distribution of heavy metals in the chemical fractions of sewage sludge, the percentage share for each element was calculated and the potential ecological risk analysis was conducted. This was possible thanks to the fact that the material used for production of ERM-CC144 (JRC) is sewage sludge of domestic origin. The obtained results revealed that ultrasound treatment does not significantly influence the distribution of analysed heavy metals in the chemical fractions of sewage sludge, with one exception, i.e., Zn. The assessment of the ecological risk was performed using Risk Assessment Code (RAC) index, which includes the content of metals in the most mobile fraction, i.e., bound to carbonates. The calculated values of RAC indicated that Zn posed the highest ecological risk. However, it can be also confirmed that the application of ultrasound treatment in the sequential extraction procedure does not have a significant impact on the interpretation of results of the ecological risk assessment. What is more, it confirms the legitimacy of using the discussed modification in the sequential extraction of heavy metals from sewage sludge.

Advanced municipal wastewater treatment and simultaneous energy/resource recovery via photo(electro)catalysis

Wastewater management and energy/resource recycling have been extensively investigated via photo(electro)catalysis. Although both operation processes are driven effectively by the same interfacial charge, each system is practiced separately since they require very different reaction conditions. In this review, we showcase the recent advancements in photo(electro)catalytic process that enables the wastewater treatment and simultaneous energy/resource recovery (WT-ERR). Various literatures based on photo(electro)catalysis for wastewater treatment coupled with CO2 conversion, H2 production and heavy metal recovery are summarized. Besides, the fundamentals of photo(electro)catalysis and the influencing factors in such synergistic process are also presented. The essential feature of the catalysis lies in effectively utilizing hole oxidation for pollutant degradation and electron reduction for energy/resource recovery. Although in its infancy, the reviewed technology provides new avenue for developing next-generation wastewater treatment process. Moreover, we expect that this review can stimulate intensive researches to rationally design photo(electro)catalytic systems for environmental remediation accompanied with energy and resource recovery.