Engineered biochar modified with iron as a new adsorbent for treatment of water contaminated by selenium

Properties and Possibilities of Using Biochar Composites Made on the Basis of Biomass and Waste Residues Ferryferrohydrosol Sorbent

Biochar enriched with metals has an increased potential for sorption of organic and inorganic pollutants. The aim of the research was to identify the possibility of using biochar composites produced on the basis of waste plant biomass and waste FFH (ferryferrohydrosol) containing iron atoms, after CO2 capture. The composites were produced in a one-stage or two-stage pyrolysis process. Their selected properties were determined as follows: pH, ash content, C, H, N, O, specific surface area, microstructure and the presence of surface functional groups. The produced biochar and composites had different properties resulting from the production method and the additive used. The results of experiments on the removal of methylene blue (MB) from solutions allowed us to rank the adsorbents used according to the maximum dye removal value achieved as follows: BC1 (94.99%), B (84.61%), BC2 (84.09%), BC3 (83.23%) and BC4 (83.23%). In terms of maximum amoxicillin removal efficiency, the ranking is as follows: BC1 (55.49%), BC3 (23.51%), BC2 (18.13%), B (13.50%) and BC4 (5.98%). The maximum efficiency of diclofenac removal was demonstrated by adsorbents BC1 (98.71), BC3 (87.08%), BC4 (74.20%), B (36.70%) and BC2 (30.40%). The most effective removal of metals Zn, Pb and Cd from the solution was demonstrated by BC1 and BC3 composites. The final concentration of the tested metals after sorption using these composites was less than 1% of the initial concentration. The highest increase in biomass on prepared substrates was recorded for the BC5 composite. It was higher by 90% and 54% (for doses of 30 g and 15 g, respectively) in relation to the biomass growth in the soil without additives. The BC1 composite can be used in pollutant sorption processes. However, BC5 has great potential as a soil additive in crop yield and plant growth.

A critical review on selenium removal capacity from water using emerging non-conventional biosorbents

Anthropogenic-driven selenium (Se) contamination of natural waters has emerged as severe health and environmental concern. Lowering Se levels to safe limits of 40 μg-L-1 (recommended by WHO) presents a critical challenge for the scientific community, necessitating reliable and effective methods for Se removal. The primary obectives of this review are to evaluate the efficiency of different biosorbents in removing Se, understand the mechanism of adsorption, and identify the factors influencing the biosorption process. A comprehensive literature review is conducted to analyze various studies that have explored the use of modified biochars, iron oxides, and other non-conventional biosorbents for selenium removal. The assessed biosorbents include biomass, microalgae-based, alginate compounds, peats, chitosan, and biochar/modified biochar-based adsorbents. Quantitative data from the selected studies analyzed Se adsorption capacities of biosorbents, were collected considering pH, temperature, and environmental conditions, while highlighting advantages and limitations. The role of iron impregnation in enhancing the biosorption efficiency is investigated, and the mechanisms of Se adsorption on these biosorbents at different pH levels are discussed. A critical literature assessment reveals a robust understanding of the current state of Se biosorption and the effectiveness of non-conventional biosorbents for Se removal, providing crucial information for further research and practical applications in water treatment processes. By understanding the strengths and limitations of various biosorbents, this review is expected to scale-up targeted research on Se removal, promoting the development of innovative and cost-effective adsorbents, efficient and sustainable approaches for Se removal from water.

Clean water production from plastic and heavy metal contaminated waters using redox-sensitive iron nanoparticle-loaded biochar

The unceasing release of tiny plastics (microplastics and nanoplastics) and their additives, like metal ions, into the aquatic systems from industries and other sources is a globally escalating problem. Their combined toxic effects and human health hazard are already proven; hence, their remediation is requisite. This study utilised the nano-zerovalent iron-loaded sugarcane bagasse-derived biochar (nZVI-SBC) for simultaneous removal of Nanoplastics (NPs) of different functionality and size along with metal ions (Ni2+, Cd2+, AsO43-, and CrO42-). Batch and column experiments were conducted, and the results showed an efficient removal of contaminants with maximum sorption of carboxylate-modified NPs of size 500 nm (qmax = 90.3 mg/g) among all three NPs types. Significant removal was observed in Cd2+ in case of cations and CrO42- in case of anions with qmax = 44.0 and 87.8 mg/g, respectively. Kinetics and the isotherm modelling better fitted the pseudo-second-order kinetic model and Sips isotherm model, respectively for both NPs and metal ions. The designed material worked well in pH range of 4-8, ionic strength 1-20 mM and in complex aqueous matrices, with >90% removal. FTIR, zeta potential and the imaging analysis of the reaction precipitates confirmed the electrostatic attraction, pore retention and complexation as the potential mechanisms for removing NPs, whereas, XPS studies confirmed the reduction co-precipitation and surface complexation as the possible mechanism for removing metal ions. High values of attachment efficiency factor calculated from colloidal filtration theory (CFT) validated the experimental results and justified the high sorption of carboxylate modified 500 nm NPs particles. The synthesized material successfully removed both NPs of varying size and functionality and metal ions simultaneously with significant efficacy in complex environmental samples proving the broad applicability of material in realistic environmental conditions and different types of water treatment processes.

Enhancing the Mn-Removal Efficiency of Acid-Mine Bacterial Consortium: Performance Optimization and Mechanism Study

In this study, an acclimated manganese-oxidizing bacteria (MnOB) consortium, QBS-1, was enriched in an acid mine area; then, it was used to eliminate Mn(Ⅱ) in different types of wastewater. QBS-1 presented excellent Mn removal performance between pH 4.0 and 8.0, and the best Mn-removal efficiency was up to 99.86% after response surface methodology optimization. Unlike other MnOB consortia, the core bacteria of QBS-1 were Stenotrophomonas and Achromobacter, which might play vital roles in Mn removal. Besides that, adsorption, co-precipitation and electrostatic binding by biological manganese oxides could further promote Mn elimination. Finally, the performance of the Mn biofilter demonstrated that QBS-1 was an excellent inoculant, which indicates good potential for removing Mn contamination steadily and efficiently.

A critical analysis of sources, pollution, and remediation of selenium, an emerging contaminant

Selenium (Se) is an essential metalloid and is categorized as emerging anthropogenic contaminant released to the environment. The rise of Se release into the environment has raised concern about its bioaccumulation, toxicity, and potential to cause serious damages to aquatic and terrestrial ecosystem. Therefore, it is extremely important to monitor Se level in environment on a regular basis. Understanding Se release, anthropogenic sources, and environmental behavior is critical for developing an effective Se containment strategy. The ongoing efforts of Se remediation have mostly emphasized monitoring and remediation as an independent topics of research. However, our paper has integrated both by explaining the attributes of monitoring on effective scale followed by a candid review of widespread technological options available with specific focus on Se removal from environmental media. Another novel approach demonstrated in the article is the presentation of an overwhelming evidence of limitations that various researchers are confronted with to overcome achieving effective remediation. Furthermore, we followed a holistic approach to discuss ways to remediate Se for cleaner environment especially related to introducing weak magnetic field for ZVI reactivity enhancement. We linked this phenomenal process to electrokinetics and presented convincing facts in support of Se remediation, which has led to emerge 'membrane technology', as another viable option for remediation. Hence, an interesting, innovative and future oriented review is presented, which will undoubtedly seek attention from global researchers.

Biochar as Sustainable Alternative and Green Adsorbent for the Remediation of Noxious Pollutants: A Comprehensive Review

The current water crisis necessitates the development of new materials for wastewater treatment. A variety of nanomaterials are continuously being investigated for their potential as adsorbents for environmental remediation. Researchers intend to develop a low-cost, simple, and sustainable material that can cater to removal of pollutants. Biochar derived from biowaste is a potential candidate for the existing problem of water pollution. The review focuses on the various aspects of biochar, such as its sources, preparation methods, mechanism, applications for wastewater treatment, and its regeneration. Compared with other adsorbents, biochar is considered as an environmentally friendly, sustainable, and cost-effective substitute for waste management, climate protection, soil improvement, wastewater treatment, etc. The special properties of biochar such as porosity, surface area, surface charge, and functional groups can be easily modified by various chemical methods, resulting in improved adsorption properties. Therefore, in view of the increasing environmental pollution and the problems encountered by researchers in treating pollutants, biochar is of great importance. This review also highlights the challenges and prospective areas that can be explored and studied in more detail in the future.

Chemical modification of biochars as a method to improve its surface properties and efficiency in removing xenobiotics from aqueous media

Biochar (BC) is a carbonaceous material produced by pyrolysis of biomass, applied in various areas such as water purification, fuel production, soil amendment, etc. Many types of BC are characterized by insufficient textural parameters or poor surface chemistry, and hence by low adsorption capacity. This makes innovative chemical methods increasing BC ability to remove xenobiotics from aquatic environments highly needed. Many of them have already been described in the literature. This review presents them in detail and evaluates their effectiveness in improving textural parameters, surface chemistry, and adsorption capacity of BC.

Influence of aluminate and silicate on selenate immobilization using alkaline-earth metal oxides and ferrous salt

Effects of aluminate and silicate species on the SeO₄^2- immobilization using alkali-earth metal oxides and ferrous species have not been clearly elucidated. In the present study, Al and Si species were separately added into MgO/Fe(II) and CaO/Fe(II) reactions containing SeO₄^2-, studied by toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray absorption fine structure (XAFS), and PHREEQC simulation. Approximately 42 % of SeO₄^2- was reduced to SeO₃^2- for MgO/Fe(II) reaction in the presence of Al species, being consistent with the case without Al species. The Al species only showed slight inhibition of Se leaching for the MgO/Fe(II) reaction. Most of Se oxyanions were adsorbed onto Mg(OH)₂ through outer-sphere complexation. For CaO/Fe(II) reaction, all of SeO₄^2- was reduced to SeO₃^2- with or without Al species. However, the Se leaching amount (3 %) of sample added with Al species (CE3) is much lower than that (12 %) of sample without Al species (CE2). This is mainly because SeO₃^2- can be sorbed onto the iron-based minerals through binuclear bidentate corner-sharing (²C) complexation instead of monodentate mononuclear corner-sharing (¹V) complexation of the case without Al species. On the other hand, SeO₄^2- was not reduced to SeO₃^2- in the presence of silicate, and almost all of Se was leached out for silicate-contained samples except CaO/Fe(II) reaction with the addition of Al species. This is due to the polymerization of Al and Si species under a high-alkalinity environment, thereby stabilizing SeO₄^2- in the amorphous silicon-aluminum structure and contributing to the decrease of Se leaching.

Effect of Pyrolysis Temperature on the Sorption of Cd(II) and Se(IV) by Rice Husk Biochar

This study investigated the removal of metal cations (Cd(II)) and metalloid anions (Se(IV)) from their aqueous solution by using agricultural waste (rice husk biochar). Rice husk biochar samples were prepared under 300, 500, and 700 °C pyrolysis conditions and their physicochemical properties were characterized. Aqueous Cd(II) and Se(IV) sorption kinetics and isotherms of rice husk biochar were studied. The results showed that the yield of rice husk biochar decreased from 41.6% to 33.3%, the pH increased from 7.5 to 9.9, and the surface area increased from 64.8 m²/g to 330.0 m²/g as the pyrolysis temperature increased from 300 °C to 700 °C. Under the experimental conditions, at increasing preparation temperatures of rice husk biochar, the sorption performance of Cd(II) and Se(IV) was enhanced. The sorption capability and sorption rate were considerably higher and faster for Cd(II) ions than for Se(IV) ions. Cd(II) sorption was found to reach equilibrium faster, within 150 min, while Se(IV) sorption was slower and reached equilibrium within 750 min. The maximum sorption capacities of cadmium and selenium by rice husk biochar were 67.7 mg/g and 0.024 mg/g, respectively, according to Langmuir model fitting.

Functionalized biochars: Synthesis, characterization, and applications for removing trace elements from water

Biochar (BC) has been recognized as an effective adsorbent to remove trace elements (TEs) from water. However, low surface functionality and small pore size can limit the adsorption ability of pristine biochar. These limitations can be addressed by using functionalized biochars which are developed by physical, chemical, or biological activation of biochar to improve their physico-chemical properties and adsorption efficiency. Despite the large amount of research concerning functionalized biochars in recent decades, to our knowledge, no comprehensive review of this topic has been published. This review focuses solely on the synthesis, characterization, and applications of functionalized/engineered biochars for removing TEs from water. Firstly, we evaluate the synthesis of functionalized biochars by physical, chemical, and biological strategies that yield the desired properties in the final product. The following section describes the characterization of functionalized biochars using various techniques (SEM, TEM, EDS, XRD, XANES/NEXAFS, XPS, FTIR, and Raman spectroscopy). Afterward, the role of functionalized biochars in the adsorption of different TEs from water/wastewater is critically evaluated with an emphasis on the factors affecting sorption efficiency, sorption mechanisms, fate of sorbed TEs from contaminated environments and associated challenges. Finally, we specifically scrutinized the future recommendations and research directions for the application of functionalized biochar. This review serves as a comprehensive resource for the use of functionalized biochar as an emerging environmental material capable of removing TEs from contaminated water/wastewater.

Coupling of desorption of phenanthrene from marine sediments and biodegradation of the sediment washing solution in a novel biochar immobilized-cell reactor

The recurrent dredging of marine sediments needs the use of ex-situ technologies such as sediment washing (SW) to effectively remove polycyclic aromatic hydrocarbons. Notwithstanding, the large volumes of generated spent SW effluents require adequate treatment by employing highly-efficient, inexpensive and environmentally-friendly solutions. This study proposes the phenanthrene (PHE) desorption from sediments using Tween® 80 (TW80) as extracting agent and the treatment of the resulting spent SW solution in a biochar (BC) immobilized-cell bioreactor. The SW process reached the highest PHE removal of about 91% using a surfactant solution containing 10,800 mg L^-1 of TW80. The generated amount of spent PHE-polluted SW solution can be controlled by keeping a solid to liquid ratio of 1:4. A PHE degradation of up to 96% was subsequently achieved after 43 days of continuous reactor operation, aerobically treating the TW80 solution in the BC immobilized-cell bioreactor with a hydraulic retention time of 3.5 days. Brevundimonas, Chryseobacterium, Dysgonomonas, Nubsella, and both uncultured Weeksellaceae and Xanthobacteraceae genera were mainly involved in PHE biodegradation. A rough economic study showed a total cost of 342.60 € ton^-1 of sediment, including the SW operations, TW80 and BC supply and the biological treatment of the SW solution.

Selenium (Se) recovery for technological applications from environmental matrices based on biotic and abiotic mechanisms

Selenium (Se) is an essential element with application in manufacturing from food to medical industries. Water contamination by Se is of concern due to anthropogenic activities. Recently, Se remediation has received increasing attention. Hence, different types of remediation techniques are listed in this work, and their potential for Se recovery is evaluated. Sorption, co-precipitation, coagulation and precipitation are effective for low-cost Se removal. In photocatalytic, zero-valent iron and electrochemical systems, the above mechanisms occur with reduction as an immobilization and detoxification process. In combination with magnetic separation, the above techniques are promising for Se recovery. Biological Se oxyanions reduction has been widely recognized as a cost-effective method for Se remediation, simultaneously generating biosynthetic Se nanoparticles (BioSeNPs). Increasing the extracellular production of BioSeNPs and controlling their morphology will benefit its recovery. However, the mechanism of the microbial production of BioSeNPs is not well understood. Se containing products from both microbial reduction and abiotic methods need to be refined to obtain pure Se. Eco-friendly and cost-effective Se refinery methods need to be developed. Overall, this review offers insight into the necessity of shifting attention from Se remediation to Se recovery.

Lead adsorption and antibacterial activity using modified magnetic biochar/sodium alginate nanocomposite

Biochar is one of the most promising wastewater treatment materials. As shown in the Scanning Electron Micrograph, the magnetic biochar (BC) cross-linked glutaraldehyde (G) with sodium alginate (SA) (BC-G-SA) nanocomposite formed with uniform particle size without aggregation, and an X-Ray Diffraction study revealed that the BC-G-SA nanocomposite has an amorphous structure. The BC-G-SA nanocomposite enhanced the microwave adsorption process for Pb (II). The maximum metal capacity value was obtained using the microwave adsorption technique at pH 5.0 and contact time 20 s for Pb (II) at medium and low microwave power (940 and 1400 μmol g^-1, respectively). Pb (II) adsorption isotherm follows a pseudo-second-order model. Also, the BC-G-SA nanocomposite effectively inhibited bacterial growth throughout the growth kinetics experiment. BC-G-SA inhibited the growth of S. aureus at a MIC of 200 g mL^-1, whereas L. monocytogenes had a MIC of 200 g mL^-1. The MIC values for E. faecalis and E. faecium were significantly lower (50 and 100 g mL^-1, respectively).

Selenium removal from water using adsorbents: A critical review

Selenium (Se) has become an increasingly serious water contamination concern worldwide. It is an essential micronutrient for humans and animals, however, can be extremely toxic if taken in excess. Sorption can be an effective treatment for Se removal from a wide range of water matrices. However, despite the synthesis and application of numerous adsorbents for remediation of aqueous Se, there has been no comprehensive review of the sorption capacities of various natural and synthesized sorbents. Herein, literature from 2010 to 2021 considering Se remediation using 112 adsorbents has been critically reviewed and presented in several comprehensive tables including: clay minerals and waste materials (presented in Table 1); zero-valent iron, iron oxides, and binary iron-based adsorbents (Table 2); other metals-based adsorbents (Table 3); carbon-based adsorbents (Table 4); and other adsorbents (Table 5). Each of these tables, and their relevant sections, summarizes preparation/modification methods, sorption capacities of various Se adsorbents, and proposed model/mechanisms of adsorption. Furthermore, future perspectives have been provided to assist in filling noted research gaps for the development of efficient Se adsorbents for real-world applications. This review will help in preliminary screening of various sorbent media to set up Se treatment technologies for a variety of end-users worldwide.

Adsorption of Arsenic on Fe-Modified Biochar and Monitoring Using Spectral Induced Polarization

This work demonstrates the potential of Fe-modified biochar for the treatment of arsenic (As) simulated wastewater and the monitoring of adsorption in real-time. Specifically, we propose the utilization of date-palm leaves for the production of biochar, further modified with Fe in order to improve its adsorption function against inorganic pollutants, such as As. Both the original biochar and the Fe-modified biochar were used for adsorption of As in laboratory batch and column experiments. The monitoring of the biochar(s) performance and As treatment was also enhanced by using the spectral induced polarization (SIP) method, offering real-time monitoring, in addition to standard chemical monitoring. Both the original and the Fe-modified biochar achieved high removal rates with Fe-modified biochar achieving up to 98% removal of As compared to the 17% by sand only (control). In addition, a correlation was found between post-adsorption measurements and SIP measurements.

Materials interacting with inorganic selenium from the perspective of electrochemical sensing

Inorganic selenium, the most common form of harmful selenium in the environment, can be determined using electrochemical sensors, which are compact, fast, reliable and easy-to-operate devices. Despite progress in this area, there is still significant room for developing high-performance selenium electrochemical sensors. To achieve this, one should take into account (i) the electrochemical process that selenium undergoes on the electrode; (ii) the valence state of selenium species in the sample and (iii) modification of the sensor surface by a material with high affinity to selenium. The goal of this review is to provide a knowledge base for these issues. After the Introduction section, mechanisms and principles of the electrochemical reduction of selenium are introduced, followed by a section introducing the modification of electrodes with materials interacting with selenium and a section dedicated to speciation methods, including the reduction of non-detectable Se(VI) to detectable Se(IV). In the following sections, the main types of materials (metallic, polymers, hybrid (nano)materials…) interacting with inorganic selenium (mostly absorbents) are reviewed to show the diversity of properties that may be endowed to sensors if the materials were to be used for the modification of electrodes. These features for the main material categories are outlined in the conclusion section, where it is stated that the engineered polymers may be the most promising modifiers.

Preparation of Si-Mn/biochar composite and discussions about characterizations, advances in application and adsorption mechanisms

A novel Si-Mn binary modified biochar composite material (SMBC) was prepared after being sintered 450 °C for 2 h. The crystal structure, surface functional groups, surface morphology and element composition, specific surface area and pore structure were characterized by XRD, FTIR, XPS, SEM + EDS and BET etc. The results showed that the surface of SMBC was rough and loose, and the specific surface area increased to 35.4284 m²/g. Si and Mn were uniformly attached to the surface of biochar in the form of SiO₂, MnO_x, MnSiO₃. Batch adsorption experiments showed that SMBC had a higher removal efficiency (139.06 mg/g, above 98%) for Cu(II) when the dosage was 2 g/L and pH = 6. The cycle experiments showed that SMBC had good reusability, and its regeneration efficiency still reached 80.24%. The leaching amount of Mn (0.65 mg/L) was greatly reduced and avoid second-pollution resulted from ion exchange, which was attributed to the existence of Si-O-Mn bonds, and they could help Mn adhere to the surface of biochar more stable. The adsorption process was dominated by single-layer chemical adsorption and mainly occurred in the membrane diffusion stage. Cu(II) mainly formed -COOCu, -OCu, Cu(OH)₂, Cu(OH)₂CO₃, Si-O-Cu, Mn-O-Cu by the mechanisms such as precipitation (4.74%), ion exchange (13.81%), complexation and physical adsorption (total 81.45% of the two mechanisms). Among them, complexation was dominant in the adsorption process.

Insights into ferulic acid detoxification mechanism by using a novel adsorbent, AEPA250: The microinteraction of ferulic acid with AEPA250 and Saccharomyces cerevisiae

In this study, a novel adsorbent, Air Environment-prepared Adsorbent at 250 ℃ (AEPA₂₅₀), was used to detoxify the main fermentation inhibitor (ferulic acid) present in the alkali-pretreated hydrolysate. AEPA₂₅₀ reduced the effective concentration of ferulic acid by its adsorption, thereby decreasing the possible interaction of ferulic acid with Saccharomyces cerevisiae. The results indicated that AEPA₂₅₀ functionalized with hydroxyl, carboxyl, and amino groups under acidic conditions with higher binding energies (-45.667, -27.046, and -11.008 kcal mol^-1, respectively) and electronic cloud overlap and shorter bond distances (1.015, 1.010, and 2.094 Å, respectively) than those under the other pH conditions. These differences revealed that the electrostatic interaction dominated ferulic acid adsorption on AEPA₂₅₀. Additionally, under acidic conditions and for carboxyl group functionalized AEPA₂₅₀, energy band gap values of Eg1 were higher than those of Eg2, indicating that ferulic acid provided the π-electrons for the π-π electron donor-acceptor interactions with AEPA₂₅₀. Furthermore, ferulic acid detoxification after AEPA₂₅₀ adsorption caused the regulation of YDR316W-B and YPR137C-B genes of S. cerevisiae. These results might contribute to the development of other more efficient adsorbents and pretreatment methods and allow yeast engineering for improving the scale-up and self-sufficient production of bioethanol in the future.

Cellulose/Biochar Cryogels: A Study of Adsorption Kinetics and Isotherms

The objective of this work was to characterize and study the behavior of the adsorption process of cellulose/biochar cryogels through isotherm models and adsorption kinetics. The cryogels were produced from a cellulose suspension obtained by mechanical fibrillation of 0.75 and 1.5% w/w unbleached long-fiber cellulose of the Pinus elliotti species. Into this suspension, 5, 10, and 20% w/w (relative to cellulose mass) biochar were added; then, the suspension was frozen and freeze-dried. After this, 2 mL of methyltrimethoxysilane (MTMS) was deposited on the cryogels. Characterization analyses were performed on the cryogels, including specific mass and porosity and sorption capacity, in addition to the study of adsorption kinetics and isotherms. The cryogels showed a porosity of above 90% and a specific gravity of less than 0.035 g cm^-3. The heterogeneous sorption capacity varied according to the concentration of cellulose used, and with the addition of 5% w/w biochar in the cellulose cryogel, the highest sorption capacity was obtained, 73 g g^-1 of petroleum and 54 g g^-1 of SAE20W50 oil. In the study of adsorption isotherms, the Freundlich model best fitted the process. Therefore, it was concluded that the process of petroleum adsorption by the cellulose cryogel occurs in multiple layers. In addition, the cellulose/biochar cryogel developed in the present work is suitable for use in the adsorption of organic liquids.