Superior reduction and immobilization of Cr(VI) in soil utilizing sulfide nanoscale zero-valent iron supported by phosphoric acid-modified biochar: Efficiency and mechanism investigation

Strategy for enhanced soil lead passivation and mitigating lead toxicity to plants by biochar-based microbial agents

In the study, bone char (BC) backed biochemical composite coupling with phosphate-solubilizing bacteria (CFB1-P) was prepared to explore the passivation performance of lead (Pb) in soil and the mitigation effect on plant growth under Pb stress by measuring change of soil Pb speciation, plant growth parameters and physiological and biochemical indexes. After 30 d of remediation, addition of 1 % CFB1-P could effectively reduce 55.43 % of Pb labile fractions and converted them into Fe-Mn oxide and residual forms. Meanwhile, the bioavailability of Pb was not significantly affected by wetting-drying and freezing-thawing after 20 times cycles (the DTPA-Pb content only increased 6.91-7.35 mg/kg), which proved that the CFB1-P had an excellent prospect of passivating Pb. Moreover, the CFB1-P effectively increased soil fertility and improved soil enzyme activity. The application of CFB1-P could reshape the soil microbial community by recruiting beneficial microorganisms (Bacillus, Sulfurifustis, and Gaiella), which contributed to the improvement of Pb-contaminated soil quality. Furthermore, the fresh weight, photosynthetic pigment concentration, stems and roots length of cucumber seedings were significantly increased. Pb in the cucumber seedings and antioxidant enzyme activities of cucumber seedings were prominently decreased. Therefore, the study can offer a preferable comprehending for the advance of sustainable high-efficiency materials which microbial agent based on functional biochar remediated Pb-polluted soil.

Preparation of superhydrophilic functionalized nZVI-MOF-74(Co)-PDA@PVDF composite membranes for enhanced Cr(VI) removal

Nano-zero-valent iron (nZVI) is widely employed in heavy metal wastewater treatment; however, it oxidizes and agglomerates readily, forming dense oxide shells that significantly diminish its effectiveness and reduction efficiency. Furthermore, the complete recovery of nZVI from water remains challenging. To address these issues, we successfully integrated nZVI onto the metal-organic framework Co-MOF-74. The framework, rich in pore channels, facilitates the uniform dispersion of nZVI, while open metal sites provide electrons crucial for the reduction of Cr(VI). Subsequently, we synthesized superhydrophilic nZVI-MOF-74(Co)-PDA@PVDF composite membranes (FMPP membranes) by incorporating nZVI-MOF-74(Co) particles into poly(dopamine) (PDA)-modified poly(vinylidene difluoride) (PVDF) powders. These nZVI-MOF-74(Co)-PDA@PVDF composite membranes feature abundant PDA functional groups, such as -OH, -NH, and -NH2, which enhance membrane hydrophilicity and significantly improve oxidation resistance. The equilibrium adsorption capacity for Cr(VI) was 83.12 mg/g at 25°C. The Cr(VI) removal behavior of the FMPP membrane aligns with the pseudo-second-order kinetic model and the Weber-Morris model. The FMPP membrane offers advantages of high efficiency, stability, and reusability. This study demonstrates that FMPP membranes hold great potential for broad application in heavy metal wastewater treatment.

Reduction-stabilization characteristics, long-term stability and biotoxicity evaluation of Fe(II)/Al layered double hydroxides on Cr(VI) in contaminated soil

Chromium(Cr) poses a significant challenge for soil remediation due to its varying oxidation states, which often result in insufficient long-term effectiveness. In this study, Fe/Al-LDH with an excellent reduction-stabilization effect was synthesized for the remediation of Cr(VI)-contaminated soil, and long-term incubation experiments were conducted over 360 days. The Cr(VI) concentration in both soil types decreased significantly, with stabilization efficiencies reaching 99.82 % and 87.93 %, respectively. Even after multiple freeze-thaw and dry-wet cycles, the leaching concentrations of BS and YS soils remained within the corresponding standard limits after remediation. Moreover, the application of Fe/Al-LDH significantly enhanced plant germination indices, particularly root length. Furthermore, results from in vitro bioaccessibility and soil film diffusion gradient extraction experiments indicated a notable reduction in Cr bioaccessibility within the treatment group. Following remediation, soil enzyme activity, microbial species richness, and diversity increased. The relative abundance of Bacillus, a key Cr(VI)-reducing microorganism, rose from 17.57 % to 19.46 %-30.24 %, further contributing to the synergistic remediation of Cr pollution. Hence, this study provides technical support for the economic, environmentally friendly, and efficient remediation of Cr(VI) pollution control projects.

Sodium citrate-modification enhanced Fe3S4 for Cr(Ⅵ) removal from aqueous solution and soil

Fe3S4 has been widely employed to remove Cr(Ⅵ) from wastewater, however, its practical effectiveness is often limited by agglomeration and passivation. This study introduces sodium citrate (SC) as a ligand to synthesize an Fe3S4-SC magnetic micro-crystal for Cr(Ⅵ) removal from aqueous solutions and contaminated soils. Experimental results show that Fe3S4-SC exhibits superior Cr(Ⅵ) removal efficiency, especially in acidic environments, with a maximum adsorption capacity of 449.12 mg/g. When Fe3S4-SC was used to remediate Cr(Ⅵ)-contaminated soil with a Cr(Ⅵ) content of 664.98 mg/kg and a TCLP-Cr(Ⅵ) concentration of 26.57 mg/L, the removal efficiencies of Cr(Ⅵ) and TCLP-Cr(Ⅵ) were 99.29% and 98.52% after 60 days. Cr speciation shifted from exchangeable fraction and weak acid-soluble fraction to more stable species bound to Fe-Mn oxides and residual fraction. Cr(Ⅵ) removal was primarily facilitated by surface Fe(Ⅱ), dissolved Fe(Ⅱ), and surface S(-Ⅱ). Surface S(-Ⅱ) provided electrons to Fe(Ⅲ), facilitating Fe(Ⅱ) regeneration for the continuous reduction of Cr(Ⅵ). The SC ligand enhanced material dispersion and stability, promoted Fe(Ⅱ) dissolution, reduced passivation layer formation, and improved electron transfer efficiency, thus increasing the efficacy of Fe3S4-SC in Cr(Ⅵ) removal. These findings provide a valuable reference for effectively remediating Cr(Ⅵ) contamination in wastewater and soil.

Tomato sprayed monocalcium phosphate had production-phytoremediation dual function with high soil Cd extraction and safer fruit production

In order to make use of the large biomass of tomato plant to fulfill the purpose of remediating-while-producing, two commercial tomato varieties, 'Baiguoqiangfeng' (BG) and 'Ouguan' (OG) were grown in Cd contaminated acidic soil to compare their performance on Cd phytoextraction, and monocalcium phosphate (Ca) was foliar applied to reduce their fruit Cd concentration. The results showed that the BG was a more Cd tolerant variety, comparing with OG, it suffered lighter tissue peroxidation and photosynthesis obstacle, owning weaker amino acid metabolism, secondary metabolism and stress signal transduction under Cd stress. The Ca application reduced its ABA level but increased the GSH, IAA, ZR and GA3 level, and enhanced its lysine degradation, tyrosine metabolism, alanine, asparagine and glutamate metabolism, plant hormone signal transduction and phenylpropanoid biosynthesis under Cd stress. With these metabolic regulations, the Ca application promoted its leaf biomass accumulation, guaranteeing the total Cd extraction amount (0.88 mg pot-1 as 0.20 mg kg -1), and reduced the fruit Cd partition, decreasing the fruit Cd concentration by 71.4% with higher yield. Meanwhile, the OG had lower Cd phytoextraction capacity than the BG, and Ca spray enhanced its cell energy generation, flavonoids biosynthesis and photosynthetic carbon fixation, but had no effect on fruit Cd concentration. The two tomato varieties had different responses to Ca application under Cd stress in their hormone signaling, energy metabolism, secondary metabolism and amino acids metabolism, which furtherly differed their Cd phytoextraction capacity and production safety. Therefore, the monocalcium phosphate spray combined 'Baiguoqiangfeng' tomato realized the dual function of production-phytoremediation, and the mechanism of plant Cd sensitivity adjustment through phenylpropanoid biosynthesis and amino acids metabolism deserved further study.

Ultra-efficient removal of aqueous hexavalent chromium by activated biochar nanoparticles derived from squid ink

Biochar have been recognized as efficient and renewable carbon sorbents, which attracted much attention on Cr contamination remediation in wastewater. In this study, we propose a cost-effective one-step strategy to synthesize activated biochar nanoparticles derived from squid ink (AS-BC) for aqueous Cr(VI) removal. The results demonstrated that AS-BC achieved a removal rate of 24.29 h-1 at 700 °C (400-times higher than the unmodified one). This was also a state-of-the-art removal performance for aqueous Cr(VI) compared to other reported materials. AS-BC possessed an enormous specific surface (2408 m2/g at 700 °C) with abundant O- and N-containing groups, condensed aromatic structures, and high electron transfer capacity (3.64 and 2.13 mmol e-/g for EAC and EDC at 700 °C), contributing to the ultra-efficient removal of Cr(VI) by synergistic adsorption and reduction. AS-BC absorbed Cr(VI) in the form of HCrO4- by electrostatic attraction with protonated amine-N and hydroxy (-NH3+ and -OH2+) groups and Cr(III) in the form of Cr3+ by complexation with amine-N and hydroxy groups. With a hydroxy-quinone and conjugated π-electron system, AS-BC served as mediator and shuttle to accelerate electron transfer in Cr(VI) reduction with an electron donor. Therefore, our findings highlight the immense potential of AS-BC biochar nanoparticles represent a potential alternative for high-performance Cr(VI) remediation in wastewater.

A novel sequential extraction method for the measurement of Cr(VI) and Cr(III) species distribution in soil: New insights into the chromium speciation

The distribution characteristics of Cr(VI) species in contaminated soil is crucial for soil remediation; however, there is currently a lack of methods for analysing anionic Cr(VI) species in soil. This study has developed a novel sequential extraction method for speciation of Cr(VI) and Cr(III). Besides extraction experiments, simulated chromium species were prepared to verify the presence of proposed chromium species. The results show that Cr(VI) species in soil can be categorized into water-soluble Cr(VI), electrostatically adsorbed Cr(VI), Cr(VI) specifically adsorbed by minerals containing exchangeable Ca2+, Cr(VI) specifically adsorbed by hydrous metal oxides, calcium chromate Cr(VI) and stable complexed adsorption Cr(VI). These Cr(VI) species can be selectively extracted by specific solutions through ion exchange or weak acid dissolution. The most stable Cr(VI) species is Cr(VI) complexed by hydrous iron oxides through bidentate ligand binding; only by dissolution of hydrous iron oxides can this Cr(VI) species be leached. The distribution of Cr(VI) species is closely linked to particular soil compositions including exchangeable Ca2+ and hydrous iron oxides which determinate the Cr(VI) adsorption in soil. Cr(III) species comprise Fe-Cr coprecipitate hydroxides Cr(III), Fe-Mn oxide-bound Cr(III), organic matter-bound Cr(III) and residual Cr(III). Their distribution depends on the types of reductants present in the soil.

Effective removal of Cr(VI) from water by ball milling sulfur-modified micron zero-valent iron：Influencing factors and removal mechanism

To address the issues of ZVI's susceptibility to oxidation and aggregation, ball milling and Na2S·9H2O modification were employed on ZVI to enhance its efficiency in removing Cr(VI) from effluent. The characterization results expressed that S-mZVIbm had mesoporous and macroporous structures, enabling successful capture of Cr(VI). Moreover, S-mZVIbm had the highest adsorption capacity for Cr(VI) (350.04 mg/g) at pH = 2.00 and reached kinetic equilibrium within 420 min. Furthermore, the adsorption of Cr(VI) by S-mZVIbm conformed to the Avrami-fractional-order model, demonstrated that the adsorption process indicated a complex multi-adsorption process. Meanwhile, the adsorption also fit to Langmuir and Sips models, suggesting monolayer-level adsorption with heterogeneous sites located on S-mZVIbm. The S-mZVIbm could enhance Cr(VI) adsorption through various synergistic mechanisms, such as electrostatic interaction, chemical precipitation, surface complexation, and reduction. Overall, this research presented an innovative perspective for the modification of ZVI, and S-mZVIbm could be widely applied in the practical remediation of wastewater containing Cr(VI).

Effect of metal-modified sewage sludge biochar tubule on immobilization of chromium in unsaturated soil: Groundwater table fluctuations induced by rainfall

Many studies have studied biochar immobilizing chromium (Cr) in soil. However, few studies were conducted to reduce the environmental risks due to biochar aging in soil. In this study, we adopt FeCl3, MgCl2, and AlCl3 to activate sewage sludge to form modified biochar and produce biochar tubules. Then, the column experiments were carried out to study the effect of fluctuating groundwater table on Cr leaching behavior, total Cr, and fractions distribution with the insertion of biochar tubule. Results showed that the Cr immobilization performance was improved by metal-modification biochar, the biochar tubules can significantly decrease the Cr leaching amounts, retard the Cr downward migration in the soil, and there was a better effect with slightly Cr-contaminated soil. In addition, the immobilization effect is also impacted by the biochar's application mode and the hydrodynamic conditions. Detailedly, the Cr leaching amounts maximally decreased by 33.39%, the residual amounts maximally increased by 10.05% in the soil column, and the exchangeable (EX) and carbonates-bound (CB) fractions were maximally increased by 85.18%, 151.78% at the equal depth of soil column, respectively. BET, SEM-EDS, XRD, and FTIR analyses revealed that biochars' immobilization mechanisms on Cr involved reduction(predominately), physisorption, precipitation, and complexation. Risk assessment demonstrated that the sewage sludge biochar has very low environmental risk. This study indicates that the biochar tubule applied to immobilize Cr in soil has potential and provides new insights into reducing environmental risks due to biochar aging.

Synergistically active Fe3O4 magnetic and EDTA modified cellulose cotton fabric using chemical method and their effective pollutants removal ability from wastewater

A unique combination of cotton fabric (CF) with a mixture of EDTA and APTES Fe3O4 magnetic particles was developed and utilized for the first time as an adsorbent for removing pollutants from wastewater. Initially, Fe3O4 was synthesized using the co-precipitation method. Further, the surface of Fe3O4 was modified by introducing amino functional groups through a reaction with APTES, resulting in Fe3O4-NH2. Following this, the surface of carbon fiber (CF) was altered using ethylenediaminetetraacetic acid (EDTA) to create CF@EDTA. Through the use of EDC-HCl and NHS, Fe3O4-NH2 was attached to the surface of CF@EDTA, resulting in the final product CF@EDTA/Fe3O4. Subsequently, the prepared CF@EDTA/Fe3O4 was utilized to adsorb metal pollutants from wastewater, with a thorough analysis conducted using various characterization techniques including FTIR, SEM, EDX, XRD, VSM, and XPS to study the materials. The study specifically aimed to assess the adsorption performance of our cotton-based material towards As(III) and Cr3+ metal ions. The pH study was also performed. Results indicated that the material exhibited an adsorption capacity of approximately 714 mg/g for As(III) ions and 708 mg/g for Cr3+ ions. The Langmuir and Freundlich models, as well as pseudo-first and second-order models were also analyzed. The Langmuir and pseudo-second-order models were found to best fit the data. In terms of regeneration and reusability, the materials showed straightforward regeneration and recyclability for up to 15 cycles. The remarkable adsorption capacity, combined with the unique blend of cotton and Fe3O4 magnet, along with its recyclability, positions our material CF@EDTA/Fe3O4 as a promising contender for wastewater treatment and other significant areas in water research.

High performance self-assembled sulfidized nanoscale zero-valent iron for the immobilization of cadmium in contaminated sediments: Optimization, microbial response, and mechanisms

Sulfidized nanoscale zero-valent iron (S-nZVI) showed excellent removal capacity for cadmium (Cd) in aqueous phase. However, the remediation effects of S-nZVI on Cd-contaminated sediment and its interactions with microorganisms in relation to Cd fate remain unclear. The complexity of the external environment posed a challenge for Cd remediation. This study synthesized S-nZVI with different S and Fe precursors to investigate the effect of precursors and applied the optimal material to immobilize Cd in sediments. Characterization analysis revealed that the precursor affected the morphology, Fe0 crystallinity, and the degree of oxidation of the material. Incubation experiments demonstrated that the immobilization efficiency of Cd using S-nZVIFe3++S2- (S/Fe = 0.14) reached the peak value of 99.54%. 1% and 5% dosages of S-nZVI significantly reduced Cd concentration in the overlying water, DTPA-extractable Cd content, and exchangeable (EX) Cd speciation (P < 0.05). Cd leaching in sediment and total iron in the overlying water remained at low levels during 90 d of incubation. Notably, each treatment maintained a high Cd immobilization efficiency under different pH, water/sediment ratio, organic acid, and coexisting ion conditions. Sediment physicochemical properties, functional bacteria, and a range of adsorption, complexation and precipitation of CdS effects dominated Cd immobilization.

Ultrafast and highly efficient Cd(II) and Pb(II) removal by magnetic adsorbents derived from gypsum and corncob: Performances and mechanisms

The utilization of gypsum and biomass in environmental remediation has become a novel approach to promote waste recycling. Generally, raw waste materials exhibit limited adsorption capacity for heavy metal ions (HMIs) and often result in poor solid-liquid separation. In this study, through co-pyrolysis with corncob waste, titanium gypsum (TiG) was transformed into magnetic adsorbents (GCx, where x denotes the proportion of corncob in the gypsum-corncob mixture) for the removal of Cd(II) and Pb(II). GC10, the optimal adsorbent, which was composed primarily of anhydrite, calcium sulfide, and magnetic Fe3O4, exhibited significantly faster adsorption kinetics (rate constant k1 was 218 times and 9 times of raw TiG for Cd(II) and Pb(II)) and higher adsorption capacity (Qe exceeded 200 mg/g for Cd(II) and 400 mg/g for Pb(II)) than raw TiG and previous adsorbents. Cd(II) removal was more profoundly inhibited in a Cd(II) + Pb(II) binary system, suggesting that GC10 showed better selectivity for Pb(II). Moreover, GC10 could be easily separated from purified water for further recovery, due to its high saturation magnetization value (6.3 emu/g). The superior removal capabilities of GC10 were due to adsorption and surface precipitation of metal sulfides and metal sulfates on the adsorbent surface. Overall, these waste-derived magnetic adsorbents provide a novel and sustainable approach to waste recycling and the deep purification of multiple HMIs.

The application of P-modified biochar in wastewater remediation: A state-of-the-art review

Phosphorus modified biochar (P-BC) is an effective adsorbent for wastewater remediation, which has attracted widespread attention due to its low cost, vast source, unique surface structure, and abundant functional groups. However, there is currently no comprehensive analysis and review of P-BC in wastewater remediation. In this study, a detailed introduction is given to the synthesis method of P-BC, as well as the effects of pyrolysis temperature and residence time on physical and chemical properties and adsorption performance of the material. Meanwhile, a comprehensive investigation and evaluation were conducted on the different biomass types and phosphorus sources used to synthesize P-BC. This article also systematically compared the adsorption efficiency differences between P-BC and raw biochar, and summarized the adsorption mechanism of P-BC in removing pollutants from wastewater. In addition, the effects of P-BC composite with other materials (element co-doping, polysaccharide stabilizers, microbial loading, etc.) on physical and chemical properties and pollutant adsorption capacity of the materials were investigated. Some emerging applications of P-BC were also introduced, including supercapacitors, CO2 adsorbents, carbon sequestration, soil heavy metal remediation, and soil fertility improvement. Finally, some valuable suggestions and prospects were proposed for the future research direction of P-BC to achieve the goal of multiple utilization.

Adsorption behavior of lead, cadmium, and arsenic on manganese-modified biochar: competition and promotion

Biochar adsorption of heavy metals has been a research hotspot, yet there has been limited reports on the effect of heavy metal interactions on adsorption efficiency in complex systems. In this study, the adsorbent was prepared by pyrolysis of rice straw loaded with manganese (BC-Mn). The interactions of Pb, Cd and As adsorption on BC-Mn were systematically studied. The results of the adsorption isotherms for the binary metal system revealed a competitive adsorption between Pb and Cd, resulting in decreased Pb (from 214.38 mg/g to 148.20 mg/g) and Cd (from 165.73 mg/g to 92.11 mg/g). A notable promotion occurred between As and Cd, showing an increase from 234.93 mg/g to 305.00 mg/g for As and 165.73 mg/g to 313.94 mg/g for Cd. In the ternary metal system, Pb inhibition did not counteract the promotion of Cd and As. Furthermore, the Langmuir isotherm effectively described BC-Mn's adsorption process in monometallic, binary, and ternary metal systems (R2 > 0.9294). Zeta and FTIR analyses revealed simultaneous competition between Pb and Cd for adsorption on BC-Mn's -OH sites. XPS analysis revealed that As adsorption by BC-Mn facilitated the conversion of MnO2 and MnO to MnOOH, resulting in increased hydroxyl radical production on BC-Mn's surface. Simultaneously, Cd combined with the adsorbed As to form ternary Cd-As-Mn complexes, which expedited the removal of Cd. These results help to provide theoretical support as well as technical support for the treatment of Pb-Cd-As contaminated wastewater.

Green synthesis of CaxLa1-xMnO3 with modulation of mesoporous and vacancies for efficient low concentration phosphate adsorption

Phosphate concentrations in eutrophic surface waters are usually low, and efficient removal of low concentration phosphate remains a challenge. In this study, Ca-doped LaMnO3 synthesized at doping ratios, designated as CaxLa1-xMnO3 (x = 0, 0.2, 0.4, 0.7), were compared. It was found that, the adsorption capacity of Ca0.4La0.6MnO3 material reached 63.01 mg/g at pH = 5, increased by 63.6% over the undoped LaMnO3 perovskite. For long-term adsorption, Ca0.4La0.6MnO3 could constantly adsorb phosphate to avoid phosphate accumulation (<0.05 mg/L). This proves that Ca0.4La0.6MnO3 has the ability to control dynamic water eutrophication. Characterization and density functional theory results confirmed that CaxLa1-xMnO3 can increase the content of mesopores and oxygen vacancies, providing additional active sites. This reduces the adsorption energy of the La site, promotes electron transfer, and increases its affinity. It provides a new method for removing low-concentration phosphates.

Fe/N co-doped magnetic porous hydrochar for chromium(VI) removal in water: Adsorption performance and mechanism investigation

Four kinds of Fe/N co-doped porous hydrochar were prepared by one/two-step N-doping schemes using microwave/traditional pyrolysis methods for removing Cr(VI) from aqueous phase. Heterocyclic-N was introduced through CO(NH2)2-based hydrothermal carbonization process, which could adjust the electronic structure of the hydrochar framework. Furthermore, Fe0 and Fe3O4 were embedded into hydrochar via carbothermal reduction reaction using FeCl3 as the precursor, which improved the reducibility and magnetism of the material. The modified hydrochar exhibited pH-dependency and rapid kinetic equilibrium, and the maximal adsorption amount of magnetic porous hydrochar obtained by microwave-assisted one-step N-doping (MP1HCMW) reached 274.34 mg/g. Meanwhile, the modified hydrochar had a high tolerance to multiple co-existing ions and the removal efficiency maintained above 73.91 % during five regeneration cycles. Additionally, MP1HCMW efficiently removed Cr(VI) via pore filling, electrostatic attraction, ion exchange, reduction, complexation, and precipitation. Summarily, Fe/N co-doped porous hydrochar was a feasible adsorbent with outstanding remediation potential for Cr(VI)-contaminated water.

Tuning active sites on biochars for remediation of mercury-contaminated soil: A comprehensive review

Mercury (Hg) contamination is acknowledged as a global issue and has generated concerns globally due to its toxicity and persistence. Tunable surface-active sites (SASs) are one of the key features of efficient BCs for Hg remediation, and detailed documentation of their interactions with metal ions in soil medium is essential to support the applications of functionalized BC for Hg remediation. Although a specific active site exhibits identical behavior during the adsorption process, a systematic documentation of their syntheses and interactions with various metal ions in soil medium is crucial to promote the applications of functionalized biochars in Hg remediation. Hence, we summarized the BC's impact on Hg mobility in soils and discussed the potential mechanisms and role of various SASs of BC for Hg remediation, including oxygen-, nitrogen-, sulfur-, and X (chlorine, bromine, iodine)- functional groups (FGs), surface area, pores and pH. The review also categorized synthesis routes to introduce oxygen, nitrogen, and sulfur to BC surfaces to enhance their Hg adsorptive properties. Last but not the least, the direct mechanisms (e.g., Hg- BC binding) and indirect mechanisms (i.e., BC has a significant impact on the cycling of sulfur and thus the Hg-soil binding) that can be used to explain the adverse effects of BC on plants and microorganisms, as well as other related consequences and risk reduction strategies were highlighted. The future perspective will focus on functional BC for multiple heavy metal remediation and other potential applications; hence, future work should focus on designing intelligent/artificial BC for multiple purposes.