Cd Removal Efficiency Research Articles

Laboratory Experiments on Remediation of Landfill Leachate Contamination with Permeable Reactive Barriers (PRBs) of Reactive Media Derived from Waste

Groundwater at landfills is often contaminated with heavy metals. Permeable reactive barrier (PRB), a potential in-situ treatment system, was investigated in this study, using 'composite reactive media' (COM), primarily composed of waste materials, to remediate heavy metals in groundwater. The COM consisted of 40% Brick and Mortar Waste (BMW), 40% Biochar (BC), 10% Granular Activated Carbon (GAC), and 10% Zeolite, based on volume. In an up-flow column, the average removal efficiencies of Fe, Pb, Cu, As, Mn, Zn, and Cd were 70.9±2.7, 80.9±3.2, 72.2±1 .6, 76.3±2.5, 81.6±6.3, 88.0±2.0, and 67.3±4.6%, respectively. In a bench-scale COM-filled PRB (0.85 x 0.25 x 0.3 m), the average removal efficiencies of the same species were 71.4±1.3, 75.4±4.9, 67.4±4.3, 72.9±1.3, 83.6±7.6, 89.8±7.4, and 80.9±7.1%, respectively. Adsorption associated with fixation, and ion exchange could be the main treatment mechanisms. COM also has potential as a filtration medium in other treatment unit processes and to treat some other types of wastewater than landfill-leachate. Further, this use of COM could alleviate the burden of disposing of BMW waste, thereby addressing a significant issue in waste management. As the identification of potential failure points in reactive media is crucial, field-scale experiments are suggested to be conducted for further investigation.

Application of coconut shell activated carbon filter in vertical subsurface flow constructed wetland for enhanced multi-metal bioremediation and antioxidant response of Salvinia cucullate

Coconut shell activated carbon (CNSAC) was applied as a filter layer in hybrid vertical subsurface flow constructed wetland (H-VSSF-CW), in order to enhance the multi-metal removal efficiency of the constructed wetland (CW) and to reduce heavy metal accumulation on Salvinia cucullata. Treatment P + AC, (having CNSAC filter layer), showed 32, 21 and 34% more Cd, Cr, and Pb removal efficiency than treatment P (without CNSAC layer). CNSAC activated carbon adsorbed Cd and Pb and Cr by functional groups –NH, -NO2, -C-O, –OH and –CO, and significantly reduced Cd and Pb exposure to S. cucullate. Chromium adsorption by CNSAC filter layer was half (just 25% of total input) of the Cd and Pb. In treatment P, due to high Cd, Pb and Cr accumulation in S. cucullate, the antioxidant defense mechanism of the plant was collapsed and cell death was observed, which in turn has resulted reduced biomass gain (5% reduction). On the other hand, in treatment P + AC, an antioxidant defense mechanism was active in the form significantly (p ≤ 0.05) increased of SOD, CAT and proline content while reduced MDA, EL, %EB and soluble sugar. So, the application of CNSAC increased the heavy metal removal efficiency of H-VSSF-CW by adsorption of a considerable share of heavy metal and hence, reduced the heavy metal load/exposure to S. cucullate.

Adsorption effect and mechanism of Cd(II) by different phosphorus-enriched biochars.

The resource utilization of agricultural and forestry waste, especially the high-value transformation of low-grade phosphate rock and derivatives, is an important way to achieve sustainable development. This study focuses on the impregnation and co-pyrolysis of rice straw (RS) with fused calcium magnesium phosphate (FMP), FMP modified with citric acid (CA-FMP), and calcium dihydrogen phosphate (MCP) to produce three phosphorous-enriched biochars (PBC). The Cd(II) removal efficiency of biochars before and after phosphorus modification was investigated, along with the adsorption mechanism and contribution of biochars modified with different phosphorus sources to Cd(II) adsorption. The result indicated that CA-FMP and MCP could be more uniformly loaded onto biochar, effectively increasing the specific surface area (SSA) and total pore volume. The adsorption of Cd(II) onto PBC followed a mono-layer chemisorption process accompanied by intraparticle diffusion. The adsorption of Cd(II) by PBC involved ion exchange, mineral precipitation, complexation with oxygen-containing functional groups (OFGs), cation-π interaction, electrostatic interaction, and physical adsorption. Ion exchange was identified as the primary adsorption mechanism for Cd(II) by BC and FBC (51.53% and 53.15% respectively), while mineral precipitation played a major role in the adsorption of Cd(II) by CBC and MBC (51.10% and 47.98% respectively). Moreover, CBC and MBC significantly enhanced the adsorption capacity of Cd(II), with maximum adsorption amounts of 128.1 and 111.5mgg-1 respectively.

Phytoremediation and environmental effects of three Amaranthaceae plants in contaminated soil under intercropping systems

Intercropping is a widely used agricultural system; however, the effect of intercropping between accumulator plants on phytoextraction in heavy metal-contaminated soils remains unknown. Here, a field experiment was conducted to investigate the phytoextraction efficiency and related environmental effects of three Amaranthaceae plants (Amaranthus hypochondriacus, Celosia argentea, and Pfaffia glomerata) using mono- and intercropping models. In monocropping, the total biomass of A. hypochondriacus was only 51.2 % of that of C. argentea. Compared with monocropping, intercropping reduced the fresh weight per plant of A. hypochondriacus by 53.0 % (intercropping with C. argentea) and 40.5 % (intercropping with P. glomerata) but increased the biomass per plant of C. argentea and P. glomerata by 128.2 and 14.2 %, respectively. The Cd uptake of the three plants in the monocropping models showed the following trend: C. argentea > P. glomerata > A. hypochondriacus. Interplanting A. hypochondriacus and C. argentea further increased the phytoextraction efficiency by 361.2 % (compared with A. hypochondriacus monocropping) and 52.0 % (compared with C. argentea monocropping). Soil exchangeable Cd, Pb, Cu, Zn, K, and P, soil N-NO3− and N-NH4+, soil common bacteria and arbuscular mycorrhiza (AM) fungi, and soil total organic carbon (TOC) play key roles in Cd and Pb uptake by the three accumulator plants (p < 0.05). The biomass of common bacteria, Gm+, Gm− bacteria, fungi, AM fungi, and actinomycetes increased with the three accumulators planted in the mono- and intercropping models. Compared with C. argentea monocropping, the biomass of soil microbes in the rhizosphere soil was obviously increased in the intercropping A. hypochondriacus and C. argentea models. These results suggest that interplanting A. hypochondriacus and C. argentea can increase Cd removal efficiency from Cd-contaminated soils, and this model could be recommended to remediate Cd-contaminated soils on a field scale.

Bioremediation of paddy soil with amphitropic mixture markedly attenuates rice cadmium: Effect of soil cadmium removal and Fe/S-cycling bacteria in rhizosphere

Cadmium (Cd) pollution in paddy soil can easily lead to excessive Cd in rice, thereby considerably threatening human health. Microbial leaching is an effective pathway for the mobilization and removal of Cd from soil. In this study, an amphitropic mixture (AM) composed of autotrophic and heterotrophic microbial strains was used to leach Cd-contaminated paddy fields. Chemical analysis showed that the AM effectively removed 52 % of the total Cd, 39 % of the available Cd, and 60 % of the exchangeable and carbonate-bound Cd from the paddy soil. After bioleaching, the Cd in the discarded AM solution was adsorbed using a metal adsorbent. Effects of remediation on the soil nutrients or secondary pollution were not significant. Microbial analysis showed that >96 % and 67 % of the indigenous bacteria and fungi, respectively, remained in the AM-remediated soil. Double-cropped rice was cultivated to evaluate the Cd removal efficiency of grains using AM remediation. The Cd in early and late brown rice decreased by 86 % and 56 %, respectively, which was higher than that found for a series of biochemical remediation materials reported in other studies. Furthermore, the AM remediation promoted the growth of iron (Fe)- and sulfur (S)-cycling bacteria in the rice rhizosphere, such as Sulfuricurvum, Desulfurivibrio and Geobacter etc., which reduced the Cd availability in the soil and rice uptake. This study shows that AM has potential applications in the remediation of Cd-contaminated paddy fields and provides a new pathway for safe rice production.

Remediation of Cd(II) contamination in aqueous solution by modified sludge biochar with molten salt-assisted pyrolysis

In this work, modified sludge biochar was prepared using molten salt-assisted pyrolysis method to remove Cd(II) from aqueous solution. The biochar was characterized using XRD, FTIR, Raman, XPS and pore structure analysis techniques, and the effects of initial pH, adsorption temperature, adsorption time and initial Cd(II) concentration on the Cd(II) removal were investigated. Compared with the virgin sludge biochar (VSBC), the modified sludge biochar (MSBC) by molten salt-assisted pyrolysis method was rougher surface, more developed pore structure and higher graphitization. The initial pH had a greater effect on the Cd(II) removal, and the high adsorption temperature promoted the Cd(II) removal. The Cd(II) removal behavior was in accordance with the pseudo-second-order kinetic model and Langmuir model, which indicated that the adsorption reaction was a single and uniform chemisorption. Thermodynamics indicated that the Cd(II) removal by VSBC and MSBC was spontaneous and heat-absorbing reaction. Additionally, the maximum adsorption capacities of Cd(II) by VSBC and MSBC were 39.02 and 101.26 mg/g at pH 5.0 and 25 °C, respectively. The mechanisms of Cd(II) removal included complexation of O-containing groups, ion exchange, precipitation, and electrostatic interaction. After three adsorption-desorption experiments, the Cd(II) removal efficiency by VSBC was maintained at 33.26%, while the Cd(II) removal efficiency on MSBC was maintained at 90.18%. This finding suggested that the modified sludge biochar using molten salt-assisted pyrolysis could be effective in remediating Cd(II)-contaminated water body.

Eco-friendly magnetic biochar from Leb Mu Nang banana peel: Response surface methodology optimization for Cd(II) adsorption from synthetic wastewater

Magnetic biochar derived from Leb Mu Nang banana peel waste is introduced as a novel precursor for Cd(II) removal from synthetic wastewater. This study comprehensively evaluates and optimizes variable factors, including initial Cd(II) concentration, magnetic biochar (MLP) dosage, adsorption time, and initial pH level, using the Response Surface Methodology (RSM). A Cd(II) removal efficiency of up to 93.4 % is reached under the conditions of a 50 mg/L initial concentration, 5 g/L MLP dosage, 24 h of adsorption time, and a solution pH of 8. The pseudo-second-order and Langmuir models accurately represent the kinetics and isotherm adsorptions, highlighting ion exchange, surface complexation, and precipitation as primary adsorption mechanisms. The magnetic biochar derived from Leb Mu Nang banana peels shows promise for efficient Cd(II) removal with easy post-adsorption separation.

Removal of sulfamethoxazole and Cu, Cd compound pollution by arbuscular mycorrhizal fungi enhanced vertical flow constructed wetlands

The combined pollution of antibiotics and heavy metals (HMs) has a serious impact on the water ecological environment. Previous researches mainly focused on the removal of antibiotics or HMs as single pollutants, with limited investigation into the treatment efficiencies and underlying mechanisms associated with their co-occurring pollution. In this study, 16 micro vertical flow constructed wetlands (MVFCWs) were constructed to treat composite wastewater consisting of sulfamethoxazole (SMX), copper (Cu) and cadmium (Cd), involving two different inoculation treatments (arbuscular mycorrhizal fungi (AMF) inoculated and uninoculated) and eight kinds of pollutant exposure (Control Check (CK), SMX, Cu, Cd, SMX + Cu, SMX + Cd, Cu + Cd, SMX + Cu + Cd). The findings of this study demonstrated that the inoculation of AMF in MVFCWs resulted in removal efficiencies of SMX, Cu, and Cd ranging from 18.70% to 80.52%, 75.18% to 96.61%, and 40.50% to 89.23%, respectively. Cu and CuCd promoted the degradation of SMX in the early stage and inhibited the degradation of SMX in the later stage. Cd did not demonstrate a comparable promotive impact on SMX degradation, and its addition hindered Cu removal. However, comparatively, the presence of Cu exerted a more pronounced inhibitory effect on Cd removal. Furthermore, the addition of Cu augmented the abundances of Proteobacteria, Bacteroidetes (at the phylum level) and Rhodobacter, Lacunisphaera and Flavobacterium (at the genus level), and Cu exposure showed a substantially stronger influence on the microbial community than that of Cd and SMX. AMF might confer protection to plants against HMs and antibiotics by enriching Nakamurella and Lacunisphaera. These findings proved that AMF-C. indica MVFCW was a promising system, and the inoculation of AMF effectively enhanced the simultaneous removal of compound pollution.

Biochar Derived from Urban Green Waste Can Enhance the Removal of Cd from Water and Reduce Soil Cd Bioavailability.

The beneficial utilization of potentially increasing urban green waste (UGW) is critical for sustainable urban development in China. In this study, UGW was pyrolyzed at different temperatures, and the resulting biochar was used to amend Cd-contaminated soils to grow cabbage. Our results showed that the Cd adsorption capacity of UGW-biochar was positively correlated with the surface area, O/C, and (O+N)/C value of biochar. Furthermore, UGW-biochar was incorporated into three Cd-contaminated soils, including one acidic soil and two neutral soils, to assess its impact on the availability of Cd. The most substantial reduction in the concentration of available Cd was observed in the acidic soil, of the three tested soils. In the neutral soils, a more substantial reduction was found in the heavily Cd-contaminated soil compared to the lightly Cd-contaminated soil. UGW-biochar amendments to the three Cd-contaminated soils resulted in an increase in the cabbage biomass in acidic soil, whereas in neutral soils, it increased in lightly contaminated soils but decreased in heavily contaminated soils. Additionally, the Cd bioaccumulation factor (BCF), translocation factor (TF), and removal efficiency (RE), as impacted by the biochar application, were calculated in the lightly Cd-contaminated soil-cabbage system. The BCF decreased from 5.84 to 3.80 as the dosage of the UGW-biochar increased from 0% to 3%, indicating that the UGW-biochar immobilized Cd and reduced its bioaccumulation in cabbage roots. Based on our investigations, UGW-biochar effectively immobilizes Cd by reducing its mobility and bioavailability in a lightly contaminated environment matrix.

Effects of biochar layer position on treatment performance and microbial community in subsurface flow constructed wetlands for removal of cadmium and lead

Levels of cadmium (Cd) and lead (Pb) correspond to common composition in acid mine wastewater of Hunan Province of China. The removal path of Cd and Pb and the structure of microbial community were investigated by developing constructed wetlands (CWs) with different layer positions of biochar. The biochar as a layer at the bottom of CW (BCW) system exhibited maximum Cd and Pb removal efficiencies of 96.6–98.6% and 97.2–98.9%, respectively. Compared with original soil, BCW increased the relative proportions of Proteobacteria, Firmicutes, Acidobacteriota, Verrucomicrobiota, Desulfobacterota, Armatimonadota, Bacteroidota, Patescibacteria, Basidiomycota (phylum level) and Burkholderia–Caballeronia–Paraburkholderia, Citrifermentans, Chthonomonadales, Cellulomonas, Geothrix, Terracidiphilus, Gallionellaceae, Microbacterium, Vanrija, Apiotrichum, Saitozyma, Fusarium (genus level). The concentrations of Cd and Pb were positively correlated with the abundance of Verrucomicrobiota, Basidiomycota (phylum level), and Methylacidiphilaceae, Meyerozyma, Vanrija (genus level). This study demonstrates that BCW system can improve removal performance toward Cd and Pb, as well as alter microbial community.

How exogenous ligand enhances the efficiency of cadmium phytoextraction from soils?

Many experiments showed that exogenous ligands could enhance cadmium (Cd) phytoextraction efficiency in soils. Previous studies suggested that the dissociation and the apoplastic uptake of Cd complex could not fully explain the increase of root Cd uptake. Two hypotheses are evaluated to explain enhanced Cd uptake in the presence of ligand: i) enhanced apoplastic uptake of complex due to reduced apoplastic resistance and ii) complex internalization by membrane transporters. Resultsshow that the ligand affinity for Cd is a key characteristic determining the potential mechanism for enhanced Cd uptake. When low molecular weight organic acids are applied, the complex dissociation could generally be fast (> 10−3.3 s−1) and result in the increased Cd uptake. When hydrophilic aminopolycarboxylic acids (APCAs) are applied in experiments without water or temperature stresses to the plant, the root water uptake flux could very likely be high (> 10−7.8 dm s−1), and the strong apoplastic complex uptake could enhance the root Cd uptake. When lipophilic APCAs are applied, the strong internalization of the complex by membrane transporters could result in the increased Cd uptake if the maximum internalization rate is high (> 10−12 mol dm−2 s−1). However, the complex internalization by membrane transporters must be experimentally confirmed.

How do different feedstocks and pyrolysis conditions effectively change biochar modification scenarios? A critical analysis of engineered biochars under H2O2 oxidation

Biochar oxidation is known as a modification method to enhance the beneficial sorption characteristics of biochar. To explore this, a comparative physio-chemical analysis of non-oxidized and oxidized biochar with hydrogen peroxide (H2O2) was conducted using different feedstocks. Biochars were pyrolyzed at temperatures of 350, 450, and 550 °C and were derived from wheat straw, rye straw, wood residues, cherry stone, sewage sludge, and cattle manure, marked as BWS, BRS, BWR, BCS, BSS, and BCM. The pyrolysis temperature of 550 °C in BWS and BRS led to the formation of newly arranged vessels and regular pores scattered in their walls. X-ray photoelectron spectroscopy of wood-based biochars showed a notable increase in surface oxygen-contained functional groups for O-BWR350, O-BWR450, O-BWR550, O-BCS350, O-BCS450, and O-BCS550 with increased values by 6.5 %, 27.9 %, 42.3 %, 3.9 %, 31.2 %, and 52.4 % compared to their correspondent non-oxidized biochars. The sharp peaks of crystallization in non-oxidized biochars diminished after oxidation as detected by X-ray diffractometer analysis. Also, Cd removal efficiency in O-BCS550 (65 %) and O-BWR550 (69 %) appeared with outstanding results among all biochar types. Based on thermo-gravimetric analysis, the lowest and highest mass losses on average were related to BRS (22.5 %), and O-BCM (39.7 %). Also, the high heating value (HHV) analysis showed that BWR550 and BCS550 biochars had the highest HHV with 33.6 and 32.5 MJ kg−1, and O-BSS350 had the lowest value with 10.1 MJ kg−1. By taking feedstock degradability and pyrolysis temperature into account, this work presents a novel approach to maximize the benefits of H2O2-modified biochar. This will enable us to create a variety of engineered biochars in a clean and economical way as opposed to costly activation oxidants.

Simultaneous immobilization of multiple heavy metal(loid)s in contaminated water and alkaline soil inoculated Fe/Mn oxidizing bacterium

Two strains of Fe/Mn oxidizing bacteria tolerant to high concentrations of multiple heavy metal(loid)s and efficient decontamination for them were screened. The surface of the bio-Fe/Mn oxides produced by the oxidation of Fe(II) and Mn(II) by Pseudomonas taiwanensis (marked as P4) and Pseudomonas plecoglossicida (marked as G1) contains rich reactive oxygen functional groups, which play critical roles in the removal efficiency and immobilization of heavy metal(loid)s in co-contamination system. The isolated strains P4 and G1 can grow well in the following environments: pH 5-9, NaCl 0-4%, and temperature 20-30°C. The removal efficiencies of Fe, Pb, As, Zn, Cd, Cu, and Mn are effective after inoculation of the strains P4 and G1 in the simulated water system (the initial concentrations of heavy metal(loid) were 1 mg/L), approximately reaching 96%, 92%, 85%, 67%, 70%, 54% and 15%, respectively. The exchangeable and carbonate bound As, Cd, Pb and Cu are more inclined to convert to the Fe-Mn oxide bound fractions in P4 and G1 treated soil, thereby reducing the phytoavailability and bioaccessible of heavy metal(loid)s. This research provides alternatives method to treat water and soil containing high concentrations of multi-heavy metal(loid)s.

W2O7 decorated polyindole nanocomposites: A dual-function platform for efficient removal and electrochemical sensing of cadmium metal ion

Our research presents a simple approach for synthesizing W2O7 decorated polyindole nanocomposites for electrochemical detection and adsorptive removal of Cd(II) ions from water. In the adsorption experiments, various parameters including temperature (ranging from 303 to 333 K), initial pH levels (ranging from 2 to 10), interaction time, amount of adsorbent (from 0.32 to 3.2 g/L), and initial concentrations (from 20 to 110 mg/L) were examined to identify the optimum conditions. The results of these studies demonstrated that the removal efficiency of Cd(II) were obtained to be 93.02% at the optimum pH of 7. Detailed adsorption isotherm and kinetic studies reveal that Cd(II) removal follows the Langmuir isotherm and pseudo-second-order (P-so) kinetic model. The PI-W2O7 NCs exhibited an estimated maximum adsorption capacity of 41.32 mg/g for Cd(II). Adsorption-desorption cycle of the Cd(II) laden PI-W2O7 NCs was effectively performed using HCl as an eluent. To enable electrochemical sensing of Cd(II) ions by PI-W2O7 NCs, the cyclic voltammetry (CV) method was employed. Intriguingly, distinct electrochemical responses were observed in our experimental observations, which stemmed from the interaction between the target analyte and the surface of PI-W2O7. The optimized conditions for the detection of Cd(II) using PI-W2O7 NCs were determined to be a concentration of 150 ppb and a pH of 7. The sensitivity and limit of detection (LOD) for Cd(II) ions were determined to be 1.719 μA/ppb cm2 and 1.072 ppb, respectively. The exceptional properties exhibited by PI-W2O7 NCs position them as a promising solution for the simultaneous detection and elimination of Cd(II) ions from water sources.

Genetic response analysis of Beauveria bassiana Z1 under high concentration Cd(II) stress

Cadmium (Cd(II)) has carcinogenic and teratogenic toxicity, which can be accumulated in the human body through the food chain, endangering human health and life. In this study, a highly Cd(II)-tolerant fungus named Beauveria bassiana Z1 was studied, and its Cd(Ⅱ) removal efficiency was 71.2% when the Cd(II) concentration was 10 mM. Through bioanalysis and experimental verification of the transcriptome data, it was found that cadmium entered the cells through calcium ion channels, and then complexed with intracellular glutathione (GSH) and stored in vacuoles or excluded extracellular by ABC transporters. Cytochrome P450 was significantly upregulated in many pathways and actively participated in detoxification related reactions. The addition of cytochrome inhibitor taxifolin reduced the removal efficiency of Cd(II) by 45%. In the analysis, it demonstrated that ACOX1 gene and OPR gene of jasmonic acid (JA) synthesis pathway were significantly up-regulated, and were correlated with bZIP family transcription factors cpc-1_0 and pa p1_0. The results showed that exogenous JA could improve the removal efficiency of Cd(II) by strain Z1.

Sorptive removal of cadmium using the attapulgite modified by the combination of calcination and iron.

Sorptive removal of cadmium (Cd) from the aqueous solutions using the easily available natural materials is an attractive method. However, the adsorption efficiencies of these materials, such as clays, are typically low. Besides, they are generally in relatively low stability and renewability, which restrict their application. Thus, modification of these materials to enhance their performance on Cd removal has gained growing attentions. Herein, the integration of calcination and ferric chloride (FeCl3) was used to modify a typical clay, i.e., attapulgite, to increase the adsorption sites, and thus to develop a robust adsorbent for Cd. Under the optimum conditions for attapulgite modification (i.e., the mass ratio of FeCl3 to attapulgite was 1:2, calcination temperature was 350 °C, and calcination time was 1.5 h) and Cd adsorption (i.e., initial pH of 6.0, adsorption temperature of 25 °C, and adsorbent dosage of 1.0 g/L), the maximum adsorption capacity of the modified attapulgite toward Cd was 149.9 mg/g. Mechanisms of surface complexation and electrostatic attraction were involved in the efficient removal of Cd. The adsorption of Cd increased with pH due to the increased electrostatic attraction. Metal cations inhibited the Cd adsorption through competing with the adsorption sites. The changes of Gibbs-free energy during the adsorption of Cd were lower than zero and decreased with temperature, suggesting the process was spontaneous and endothermic. The removal efficiency of Cd after 5 times of recycle maintained at 82% of that of the raw modified attapulgite demonstrated the stability of the adsorbent. These results suggested that the modified attapulgite is robust for Cd removal and is promising for land application.

Removal and emission characteristics of hazardous trace elements in total and graded particulate matters: A case study of a typical ultra-low emission coal-fired power plant

Particulate matters (PMs) and hazardous trace elements (HTEs) emitted from coal-fired power plants (CFPPs) have raised serious environmental and human issues. Herein, total PMs and graded PMs including PM<1, PM1–2.5 and PM2.5–10 at the inlet/outlet of air pollution control devices (APCDs) were collected from a representative ultra-low emission (ULE) CFPP in China. The removal efficiencies of total PMs by selective catalytic reduction (SCR), electrostatic precipitator (ESP), wet flue gas desulfurization (WFGD) and wet electrostatic precipitator (WESP) were 0.40 %, 99.9 %, 38.1 % and 85.3 %, respectively. PM2.5–10 was robustly removed by WFGD, while PM<1 and PM1–2.5 were readily removed by WESP. The removal efficiencies of As, Cd, Cr and Pb in total PMs by APCDs followed an order: ESP > WESP > WFGD > SCR. SCR significantly decreased Se concentration by 42.8 %, contrasting to the removal of As, Cd, Cr and Pb (10.8–20.8 %). As, Cd, Cr, Pb and Se concentrations in graded PMs at the outlets of ESP, WFGD and WESP decreased with particle size increasing. All As, Cd, Cr, and Pb contents in PM<1, PM1–2.5 and PM2.5–10 at WFGD outlet increased, surpassing their analogues at ESP and WESP outlets. However, the concentration of Se declined in PM<1 at WFGD outlet. The atmospheric emission factors (EFs) of As, Cd, Cr, Pb and Se in the studied ULE CFPP were respectively 7.32, 1.27, 6.05, 122.5 and 6.42 mg/t, in line with Monte Carlo simulations. This study would not only provide a basis for emission control of PMs and HTEs in CFPPs, but also promote the improvement of respective environmental policy.

A sustainable nanotechnology producing high-quality remediated sewage wastewater used for microalgal protein-rich biomass and biodiesel production

AbstractWater scarcity is a crucial environmental challenge. Wastewater remediation is an important way to tackle the challenge. Using nanoparticles of natural and agricultural wastes is considered a low-cost sustainable remediation technology. This study develops an effective prototype of a sustainable sewage wastewater (SWW) remediation process using zeolite and bagasse nanoparticles. All studied physico-chemical parameters and heavy metals of the SWW were reduced over the course of treatment with nanobagasse (NB), nanozeolite (NZ), and nanobagasse-nanozeolite double treatments (DT). After only 2 weeks of remediation, the chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solid (TSS), and total dissolved solid (TDS) concentrations were decreased (in NB 38, 33, 58, and 30%; in NZ 40, 30, 63, and 58%; and in DT 47, 38, 75, and 62%), respectively, compared to raw SWW. The DT for 4 and 6 weeks (DT4W and DT6W) show 0.94 and 0.67 Kelly ratios, respectively, which are suitable for irrigation. According to the water pollution index (WPI), all types of DT treatments produce excellent-quality water. DT6W recorded the highest significant rank of removal efficiency of COD, BOD, TSS, TDS, PO4, NO3, Ca, Mg, Na, Cu, Cd, Fe, and Ni (72.7, 59.6, 88.6, 74, 56.7, 88.2, 72.7, 58.7, 80.7, 94.6, 91.1, 65.3, and 84.4%). This remediated water may be used directly for irrigation or other purposes. Also, this study proves that DT4W and DT6W are suitable for Chlorella sorokiniana growth and production of safe protein-rich biomass, 26 and 31.8% protein, respectively. DT for 2, 4, and 6 weeks are suitable growth media for C. sorokiniana to produce diesel engines’ compatible biodiesel. Finally, this recent study presents an interpretation of the physiological status of C. sorokiniana cells grown in the raw SWW and DT media.

Biomass-derived carbon/iron composite (FexOy-BC (RM)) with excellent Cd(II) adsorption from wastewater – Red mud resource utilization

Red mud is an industrial by-product produced in the process of alumina refining. It contains many iron elements, and the traditional resource utilization method is to extract it. This study took an alternative approach by using red mud's iron content as the substrate to synthesize a novel iron-biochar adsorbent for removing heavy metals from wastewater. Walnut shell biochar was reacted with the iron in red mud via an in-situ reduction–oxidation process to produce an iron-carbon composite adsorbent (FexOy-BC). A series of characterization analyses (e.g., SEM, FTIR, XPS, etc.) and batch adsorption experiments were conducted to investigate the properties and Cd(II) removal performance of the adsorbent, respectively. Response surface methodology was further employed to optimize the adsorption conditions, identifying the ideal 6 g/L adsorbent dose, 10 mg/L initial Cd(II) concentration (C0), and pH 6. The optimized quadratic model demonstrated excellent fit, with an average Cd(II) removal efficiency of 92.59 % under optimal conditions. The adsorption mechanism, renewability, and preliminary cost-benefit analysis indicate that FexOy-BC has the potential to be a highly efficient and sustainable adsorbent. In summary, the new method can recover resources from red mud waste and synthesize heavy metal adsorbents, which comprehensively solves two long-standing problems of industrial waste.

Highly efficient removal of trace heavy metals by high surface area ordered dithiocarbamate-functionalized magnetic mesoporous silica.

The study describes synthesizing and characterizing a novel dithiocarbamate-functionalized magnetic nanocomposite. This nanocomposite exhibits several desirable properties, including a large pore diameter of 2.55 nm, a high surface area of 1149 m2/g, and excellent capturing capabilities. The synthesis process involves the preparation of highly porous magnetic nanocomposites, followed by functionalization with dithiocarbamate functional groups through a reaction with carbon disulfide and amine. The synthesized nanocomposite was thoroughly characterized using various techniques, including X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The performance of the mesoporous nanocomposite as an adsorbent for removing Pb(II), Cd(II), and Cu(II) cations from contaminated water was evaluated. The study finds that the maximum removal efficiency for Pb(II), Cd(II), and Cu(II) cations is achieved at pH values above 4. The optimal contact time for achieving 100% removal efficiency of the mentioned cations ranged between 60 and 120 min. Within this time range, the adsorbent exhibited efficient capture of the heavy metal cations from contaminated water. Additionally, the appropriate amount of adsorbent required for complete elimination of the heavy metal cations is determined. For Cd(II), the optimal dosage was found to be 50 mg of the adsorbent. For Cu(II), the optimal dosage was determined to be 40 mg. Finally, for Pb(II), the optimal dosage was 30 mg. The adsorbent's regeneration capability was demonstrated, showing that it could be reused for five consecutive runs.