Heavy Metal-contaminated Wastewater Research Articles

Non-radical activation of CaO2 nanoparticles by MgNCN/MgO composites for efficient remediation of organic and heavy metal-contaminated wastewater

Stable, cheap and environmentally friendly CaO2 was widely used to remediate environmental pollution, especially in advanced oxidation process (AOP) systems. However, its non-radical activation was still a huge challenge. In this study, the non-radical activation of CaO2 nanoparticles was realized by MgNCN/MgO composites for efficient remediation of organic and heavy metal-contaminated wastewater. The presented CaO2-based AOP system exhibited excellent degradation performance towards tetracycline (TC) and methylene blue (MB) over a broad pH range, accompanied with the weak influences of common coexisting anions and natural water sources. Singlet oxygen (1O2) was verified as the dominant active species for organics degradation, and the coordination between MgNCN and MgO in MgNCN/MgO composites played a crucial role in the non-radical activation of CaO2 nanoparticles. More importantly, the AOP system could not only degraded effectively organic pollutants, but also remove simultaneously heavy metal ions in wastewater. 100 mg/L CaO2 and MgNCN/MgO could successfully remediate the complex pollution consisting of 10 mg/L MB and 100 mg/L Cd2+. Furthermore, the degradation intermediates of MB and the solid residues after treating pollutants were analyzed in detail to reveal the degradation process and conversion products.

Use of Natural Zeolite and Its Mixtures to Refine High-Concentrated Heavy Metal-Contaminated Wastewater: an Investigation of Simultaneous Removal of Cd (II) and Pb (II) by Batch Adsorption Method

Use of Natural Zeolite and Its Mixtures to Refine High-Concentrated Heavy Metal-Contaminated Wastewater: an Investigation of Simultaneous Removal of Cd (II) and Pb (II) by Batch Adsorption Method

Hydroxyapatite Coatings on Calcite Powder for the Removal of Heavy Metals from Contaminated Water

An approach for the remediation of heavy metal-contaminated wastewater that is gaining increasing attention is the application of hydroxyapatite (HAP)-based particles. HAP is conventionally synthesized through wet chemical precipitation of calcium and phosphate ions, although later studies have focused on HAP synthesis from solid calcite contacted with a phosphate solution under ambient conditions. This synthesis route can allow saving soluble Ca-chemicals and, thus, make the process more cost-efficient. The aim of this study was to coat natural calcite powder with a layer of HAP for the removal of Zn and Cu from contaminated water. For this purpose, a HAP layer was synthesized on calcite particles, characterized using several complementary techniques and evaluated for the removal of Zn and Cu from synthetic solutions. Sorption kinetics and equilibrium isotherms, as well as the effect of sonication of the synthesized sample on its sorption performance, were determined. The results showed that calcite particles were efficiently coated with a HAP layer with high capacity in removing Zn and Cu from acidic solutions, with a qmax of 34.97 mg/g for Zn (increased to 37.88 g/mg after sonication of the sample) and 60.24 mg/g for Cu (which hardly varied with sonication). The mechanisms behind the sorption of Zn and Cu onto HAP, inferred from pH changes, the relation between metal uptake and Ca2+ release and XRD analysis, included surface complexation, ion exchange and precipitation of new Zn- and Cu-containing phases.

Removal of As(V), Cr(VI) and Cu(II) using novel amine functionalized composite nanofiltration membranes fabricated on ceramic tubular substrate

Novel amine functionalized composite membranes were prepared over tubular ceramic substrate using facile dip-coating and cross-flow filtration approach. The two fabricated membranes, P-60S and P-60S-EDTA with polyethyleneimine (PEI) and EDTA-modified PEI as functional layers respectively, were characterized in terms of EDX, FTIR, XPS, FESEM, AFM and contact angle analyses which confirmed their stable physical and chemical structure for use in high pressure application. Clean water permeability and MWCO study revealed the superior permeability and rejection efficiency of the P-60S-EDTA compared to the P-60S membrane. Incorporation of bulky EDTA molecules in the membrane functional layer simultaneously decreased pore size and increased membrane hydrophilicity. The removal of As(V), Cr(VI) and Cu(II) heavy metals by both membranes were found to be highly pH dependent and overall rejection improved in case of P-60S-EDTA membrane [99.82% for Cu(II), 96.75% for As(V) and 97.22% for Cr(VI)]. Interestingly, rejection of As(V) and Cr(VI) was significantly improved in presence of Cu(II) due to volume resistance provided by EDTA-Cu(II) complex towards the passage of other heavy metal ions. Excellent stability of P-60S-EDTA membrane in continuous operation of 36 h in both ideal and practical water environment suggests its promising application in real field heavy metal contaminated waste water treatment.

Effect of Heavy Metal Contaminated Waste Water Irrigation on Enzymatic and Non Enzymatic Antioxidants in Some Selected Vegetables

The study was conducted to investigate the bioaccumulation of heavy metals (As, Cd,Cr and Pb) and their effect on the antioxidant level and activity in vegetables Raphanus sativus, Spinacea oleracea, Brassica oleracea and Lycopersicum esculentum irrigated with heavy metal loaded waste water of Buddha Nullah. The results of the study revealed bioaccumulation of heavy metals in vegetables and the level of non-enzymatic antioxidants, ascorbic acid and proline and enzymatic antioxidants, catalase and peroxidase was found to be much higher in waste water irrigated vegetables in comarison to the level of bioaccumulation of heavy metals as well as antioxidants in same vegetables irrigated with normal borewell water as control. This indicates that heavy metals induce oxidative stress (ROS) in the plants at cellular level and to nullify the toxic effect these heavy metals the cell mechanism increase the production and activity of both non-enzymatic and enzymatic antioxidants.

Enhanced removal of aqueous Cd(II) by a biochar derived from salt-sealing pyrolysis coupled with NaOH treatment

Activated biochar (A-BC550) that was prepared by salt-sealing pyrolysis (at 550 °C) and coupled with NaOH treatment was used to remove cadmium (II) from an aqueous solution. The FTIR spectroscopy and XPS analysis showed that the content of carboxyl and methoxy (CH3O) groups was increased by the NaOH impregnation that occurred before pyrolysis. The complexation and precipitation that occurred played a leading role in the subsequent adsorption. Adsorption occurred on the surface of the biochar, and the adsorption equilibrium was achieved in approximately 10 min of reaction following the pseudo second-order kinetic model and the Redlich-Peterson isotherm model. The maximum adsorption capacity of A-BC550 was determined by the Sips isotherm model to be 216.2 mg g−1 at pH = 7, which was 4.6 times that of the unmodified biochar without the NaOH treatment (47.13 mg g−1). Thermodynamic parameters showed the increase of adsorption temperature was conducive to the adsorption process. This work provides a low-cost and environmentally friendly method to pyrolyze biochar. The A-BC550 is a favorable material for treating heavy metal-contaminated wastewater.

Comparison of The Sorption Kinetics of Lead(II) and Zinc(II) on Titanium Phosphate Ion-Exchanger.

The treatment of heavy metal-contaminated wastewater is an important action to reduce the negative impacts of industrial wastes on water bodies. This work focuses on the application of a low-cost titanium (IV) phosphate sorbent of TiO(OH)H2PO4·2H2O chemical composition toward lead and zinc ions depending on their concentration and the temperature of the solution. The kinetic studies showed that the values of the rate of intraparticle diffusion and the effective diffusion coefficients for Zn2+ were considerably higher than those for Pb2+. To explain the difference between the sorption kinetics rates for Pb2+ and Zn2+, the effective radius and dehydration degree of the adsorbed ions were calculated. The sorbent capability of the lead and zinc ion removal and its excellent efficiency in the presence of a high concentration of calcium ions were demonstrated using simulated mine water. Due to the fast kinetics and the high exchange capacity of titanium phosphate toward divalent ions, this sorbent can be considered as a promising material for the concentration and immobilization of heavy metals into the phosphate matrix.

Performance evaluation and optimization of flocculation process for removing heavy metal

Carboxymethyl chitosan (CMCTS) with active hydroxyl and amino groups is easily modified for chelating and capturing heavy metal, thus showing great potential for application in heavy metal-contaminated wastewater treatment. In this work, a dual-functional MACA copolymer [CMCTS-graft-P(AM-TGA)] with pH resistant was successfully designed and prepared by grafting acrylamide and thioglycolic acid onto CMCTS through UV-initiated graft polymerization. The spectroscopy characterization of functional groups and apparent morphology confirm the successful preparation of MACA. Flocculation conditions for reaching high removal efficiencies and investigating chelation capacity are optimized. A multiobjective evaluation model and a triangular environmental impact, economic benefit, and energy consumption (3E) evaluation model were established and employed to assess the 3E performance of MACA in heavy metal-contaminated wastewater flocculation. Optimal operation modulus is identified using 8 Key performance indicators by 3E triangle model. This work enriches knowledge about flocculation and provides guidance for flocculation parameter control.

Characterization of rhizosphere and endophytic bacteria from roots of maize (Zea mays L.) plant irrigated with wastewater with biotechnological potential in agriculture

The aim of this study was to characterize culturable rhizosphere and endophytic bacterial isolates isolated from rhizosphere soil and roots of maize plant irrigated with industrial and municipal wastewater in terms of resistance to heavy metals and salinity and plant growth promoting (PGP) traits. Results illustrated that both rhizosphere isolates and endophytic ones had various PGP characteristics in terms of both the number and the production amount of these characteristics. A substantial number of the bacterial isolates (both endophytic isolates and rhizosphere isolates) were tolerant to heavy metals (multi-metal resistant bacteria). Compared to endophytic isolates, rhizosphere isolates had greater resistance to heavy metals. Both endophytic isolates and rhizosphere ones showed remarkable resistance to salinity (7% NaCl). Based on comparison of 16S rRNA sequences and biochemical tests, the effective isolates, based on having multiple PGP characteristics and higher resistance to heavy metals and salinity, were identified. Isolates N5 and R7 were closely related to Bacillus cereus and Enterobacter cloacae, respectively. In addition, the ability of rhizosphere strain R7, as a multi-metal resistant bacterium, in the removal of cadmium (Cd) and lead (Pb) by its biomass and colonization of maize roots in the presence of these metals was evaluated. This strain could remove these metals from the solution (46.5–88.95%) and colonize both root surface and inside root of maize (4–7 Log10 CFU (colony–forming unit) g−1 fresh root weight) under heavy metal stress. Therefore, it can be concluded that maize plant irrigated with industrial and municipal wastewater harbors salinity and heavy metals–resistant bacteria and may be potential reservoirs for isolating bacteria effective at alleviating heavy metal stress in the plant, reducing accumulation of heavy metals in crops such as maize, and removing heavy metals in aqueous media (bioremediation of heavy metal-contaminated wastewater system).

Effects of sludge lysate for Cr(VI) bioreduction and analysis of bioaugmentation mechanism of sludge humic acid.

This study evaluated the effects of sludge lysate (SL) on the anaerobic bioreduction of Cr(VI) and the role of sludge humic acid (SHA) during this process. The results showed that supplement of SL significantly enhanced the efficiency of Cr(VI) bioreduction by 29.61%, in 12h compared with that of the control without SL. Moreover, SHA exhibited promoting effects on bioreduction of Cr(VI), and the promotion increased with increasing SHA concentrations from 100 to 300mg/L. In the presence of 300mg/L SHA, Cr(VI) (98.21mg/L) was completely reduced after 24h with a removal rate increased by 34.3% compared with that of the control without SHA. Further investigation on the bioaugmentation mechanism of SHA by studying the nature of SHA and the reaction mechanism between SHA and Cr(VI) revealed that SHA exhibited a strong adsorption ability, which could adsorb and combine with Cr(VI). The adsorption capacity of Cr(VI) by SHA was calculated as 34.4mg/g with 0.2g of SHA and 10mg/L of Cr(VI). It could also act as redox mediators to accelerate the electron transfer between microorganisms and Cr(VI) to promote reduction of Cr(VI). Furthermore, the effects of SL on the microbial community compositions of the anaerobic Cr(VI) bioreduction system were studied. Brachymonas was the primary bacteria at the genus level. The abundance of electroactive bacteria, such as Acinetobacter, Pseudomonas, and Arcobacter, increased in the SL-amended system. These findings expand the versatility of SL and justify wider use of residual activated sludge, which might contribute to the treatment of heavy metal-contaminated wastewater.

Facile one-pot hydrothermal synthesis of cubic spinel-type manganese ferrite/biochar composites for environmental remediation of heavy metals from aqueous solutions

This study reports the facile synthesis of cubic spinel-type manganese ferrite (MnFe2O4)/biochar (MF/BC) composites via a one-pot hydrothermal technique. Multiple characterizations demonstrated that the MnFe2O4 spinel nanoparticles were successfully grown on the biochar, which provides magnetic separability with superparamagnetic behavior and effective adsorption performance for heavy metals (Pb(II), Cu(II), and Cd(II)). The adsorption kinetics and isotherms can be well described with a pseudo-second-order and Sips isotherm models, respectively. Comparative adsorption in multi-heavy metal systems (binary and ternary) indicated that the adsorption affinity of MF/BC composites toward heavy metals followed the sequence of Pb(II) > Cu(II) > Cd(II), which followed the order of their covalent indexes. Thermodynamic analysis revealed that the adsorption process was endothermic and primarily governed by physisorption. This study provides a feasible and simple approach for the preparation of high-performance materials for the remediation of heavy metal-contaminated wastewater in a cost-effective manner.

Arbuscular mycorrhizal fungi in two vertical-flow wetlands constructed for heavy metal-contaminated wastewater bioremediation.

Over the last three decades, the presence of arbuscular mycorrhizal fungi (AMF) in wetland habitats had been proven, and their roles played in wetland ecosystems and potential functions in wastewater bioremediation technical installations are interesting issues. To increase knowledge on the functions of AMF in the plant-based bioremediation of wastewater, we constructed two vertical-flow wetlands planting with Phragmites australis and investigated AMF distribution in plant roots and their roles played in purification of wastewater polluted by heavy metals (HMs), utilizing the Illumina sequencing technique. A total of 17 operational taxonomic units (OTUs) from 33,031 AMF sequences were obtained, with Glomus being the most dominant. P. australis living in the two vertical-flow constructed wetlands (CWs) harbored diverse AMF comparable with the AM fungal communities in upland habitats. The AMF composition profiles of CW1 (vegetated with non-inoculated plants) and CW2 (vegetated with mycorrhizal plants inoculated with Rhizophagus intraradices) were significantly different. CW1 (15 OTUs) harbored more diverse AMF than CW2 (7 OTUs); however, CW2 harbored much more OTU13 than CW1. In addition, a zipf species abundance distribution (SAD), which might due to the heavy overdominance of OTU13, was observed across AM fugal taxa in P. australis roots of the two CWs. CW1 and CW2 showed high (> 70%) removal capacity of HMs. CW2 exhibited significant higher Cd and Zn removal efficiencies than CW1 (CK) (p = 0.005 and p = 0.008, respectively). It was considered that AMF might play a role in HM removal in CWs.

Toxic metals accumulation in Trichoderma asperellum and T. harzianum

Heavy metal contamination represents an important environmental issue due to the toxic effects of metals on different organisms. Filamentous fungi play an important impact in the bioremediation of heavy metal-contaminated wastewater and soil. The purpose of this investigation was to observe fungal uptake behavior toward heavy metal. For this aim Trichoderma asperellum TS141 and T. harzianum TS103 at growth period were screened for their tolerance and uptake capability of cadmium (Cd), lead (Pb) and nickel (Ni) at different concentrations (0, 25, 50, 100, and 200 mg/L) in PDB media (potato dextrose broth as a complex medium). Results showed that both fungi were able to survive at the maximum concentration of 200 mg/L of the heavy metals, and remove them. T. asperellum had a better uptake capacity for Cd compared to Pb and Ni in the highest metal concentration in media. Maximum removal efficiency of Pb (68.4%) at 100 mg/L and Ni (78%) at 200 mg/L was performed by T. asperellum. For Cd, the highest removal efficiency (82.1%) was recorded by T. harzianum at 200 mg/L Cd in aqueous solution. The uptake of Cd was highly dependent on pH of solution than Pb and Ni so that the optimal pH of Cd uptake was 9 for T. asperellum and 4 for T. harzianum. Also, optimal temperature was 35°C for Cd and Pb uptake in both fungi, whereas for Ni uptake was 30 and 35°C in T. harzianum and T. asperellum, respectively. We propose that T. asperellum TS141 and T. harzianum TS103 can be used as a bioremediation agent for metal remediation from wastewater and heavy metal-contaminated soils.

Biosorption and Bioaccumulation of Copper and Lead by Heavy Metal-Resistant Fungal Isolates

Microorganisms play an important role in the bioremediation of heavy metal-contaminated wastewater and soil. In this research, isolation of heavy metal-resistant fungi was carried out from wastewater-treated soil samples of Hudiara drain, Lahore. The purpose of the present investigation was to observe fungal absorption behavior toward heavy metal. The optimum pH and temperature conditions for heavy metal removal were determined for highly tolerant isolates of Aspergillus spp. along with the initial metal concentration and contact time. Biosorption capacity of A. flavus and A. niger was checked against Cu(II) and Pb(II), respectively. The optimal pH was 8–9 for A. flavus and 4–5.4 for A. niger, whereas optimal temperature was 26 and 37 °C, respectively. Moreover, the biosorption capacity of A. flavus was 20.75–93.65 mg g−1 for Cu(II) with initial concentration 200–1400 ppm. On the other hand, biosorption capacity of A. niger for Pb(II) ranged from 3.25 to 172.25 mg g−1 with the same range of initial metal concentration. It was also found that equilibrium was maintained after maximum adsorption. The adsorption data were then fitted to Langmuir model with a coefficient of determination >0.90. The knowledge of the present study will be helpful for further research on the bioremediation of polluted soil.

Selection of aquatic plants for phytoremediation of heavy metal in electroplate wastewater

The remediation of heavy metal-contaminated sites using plants is a promising alternative to current methodologies. In this study, small-scale wetlands were constructed to search for new plant species that are suitable and hold potential for phytoremediation of heavy metal-contaminated wastewater originating from an electroplating plant. Ten macrophyte species [Phragmites australis (Cav.) Trin., Typha orientalis Presl, Lythrum salicaria Linn., Arundo donax Linn. var. versicolor Stokes, Typha minima Funk, Juncus effusus L., Pontederia cordata L., Cyperus alternifolius Linn. subsp. flabelliformis (Rottb.) Kukenth., Acorus calamus Linn., and Iris pseudacorus Linn.] were investigated and compared for their shapes, biomass, roots, and ability to accumulate heavy metals. Acorus calamus Linn., T. orientalis Presl, P. australis (Cav.) Trin., T. minima Funk, and L. salicaria Linn. exhibited the highest levels of metal tolerance, whereas P. cordata L., I. pseudacorus Linn., and C. alternifolius Linn. subsp. flabelliformis (Rottb.) Kukenth. had the lowest. Some plants accumulated higher concentrations of metals in the tissues compared with other species such as T. minima Funk, P. australis (Cav.) Trin., L. salicaria Linn., A. donax Linn. var. versicolor Stokes, P. cordata L., and A. calamus Linn., whereas T. orientalis Presl and C. alternifolius Linn. subsp. flabelliformis (Rottb.) Kukenth. had poor capacity to accumulate heavy metals. The results showed that, of the 10 species, P. australis (Cav.) Trin., A. calamus Linn., T. minima Funk, and L. salicaria Linn. are the most suitable and promising plant materials for phytoremediation of heavy metal-contaminated wastewater.

Synthesis of ferrites obtained from heavy metal solutions using wet method

Wet method was employed to the treatment of heavy metal-contaminated wastewater, and Zn x Fe 3− x O 4, Ni x Fe 3− x O 4 and Cr x Fe 3− x O 4 (0 < x < 1) were synthesized. Phase identification of the prepared samples was done by X-ray diffraction (XRD), which indicates that the products are spinel-structured; transmission electron microscopy (TEM) images show that crystal size of the ferrite products synthesized is 0.1–0.4 μm. Thermostability of the products was characterized by differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). It was found that when the doped ferrite is qualified, the highest content of doped ion (Zn 2+, Ni 2+ and Cr 3+) that could enter ferrite lattice is: 0.08, 0.049 and 0.02, respectively. At low concentration the capability of doped ions entering ferrite product is Ni 2+ ≈ Zn 2+ > Cr 3+ and the influence of the three ions on sample thermostability is Zn 2+ > Ni 2+ > Cr 3+.

Long-term efficiency and stability of wetlands for treating wastewater of a lead/zinc mine and the concurrent ecosystem development

A constructed wetland system in Guangdong Province, South of China has been used for treating Pb/Zn mine discharge since 1985. The performance in the purification of the mine discharge and the concurrent ecosystem development within the system during the period of 1985–2000 has been studied. The untreated wastewater contained rather high concentrations of cadmium (Cd) (0.05 mg L −1), lead (Pb) (11.5 mg L −1), and zinc (Zn) (14.5 mg L −1), which greatly exceed the upper limits for industrial wastewater discharge in China. The constructed wetland system effectively removed Cd by 94.00%, Pb by 99.04%, Zn by 97.30%, and total suspended solids (TSS) by 98.95% from the mine discharge over a long period (over 16 years) leading to significant improvement in water quality; it was also found that there were no significantly annual or monthly variations in pH values, As, Cd, Hg, Pb, and Zn concentrations in water collected from the outlet of the wetland. Moreover, diversity and abundance of living organisms, including protozoan, higher plants, terrestrial animals, and birds, increased gradually. The 16-year monitoring results showed a reciprocal relationship, at a certain extent, between restoration of the wetland ecosystem, in other words, the maturity of the wetland, and the long-term efficiency and stability on purifying heavy metal-contaminated wastewater.

Synthesis of Al-substituted 11 Å tobermorite from newsprint recycling residue: a feasibility study

Newsprint recycling is responsible for significant volumes of secondary waste material for which further reprocessing and market development would be beneficial. In response to this problem, a layer lattice, ion exchange material, Al-substituted 11 Å tobermorite, has been synthesised from newsprint recycling residue comprising gehlenite (Ca 2Al 2SiO 7), akermanite (Ca 2MgSi 2O 7), β-dicalcium silicate (Ca 2SiO 4) and anorthite (CaAl 2Si 2O 8) under hydrothermal conditions at 100 °C in the presence of NaOH. The hydrogarnet phase, katoite (Ca 3Al 2SiO 12H 8), was also formed. Similar treatment regimes in the presence of LiOH and KOH did not yield significant quantities of Al-substituted 11 Å tobermorite. A batch sorption study confirmed that the Al-substituted 11 Å tobermorite-bearing product was effective in the exclusion of Cd 2+, Pb 2+ and Zn 2+ from acidified aqueous media. The potential to enhance the yield of Al-substituted 11 Å tobermorite relative to that of katoite and thus optimise the ion exchange efficiency of the product is discussed with respect to its application to heavy metal-contaminated wastewater treatment.