Adsorption of boron by CA@KH-550@EPH@NMDG (CKEN) with biomass carbonaceous aerogels as substrate

Recent advances in boron removal in aqueous media. An approach to the adsorption process and process optimization

The numerous oxidation states of the element boron bring great challenges in containing its contamination in receptor bodies. This scenario increases significantly due to the widespread use of boron compounds in various industries in recent years. For this reason, the removal of this contaminant is receiving worldwide attention. Although adsorption is a promising method in boron removal, finding suitable adsorbents, that is, those with high efficiency, and feasible remains a constant challenge. Hence, this review presents the boron removal methods in comparison to costs of adsorbents, reaction mechanisms, economic viability, continuous bed application, and regeneration capacity. In addition, the approach of multivariate algorithms in the solution of multiobjective problems can enable the optimized conditions of dosage of adsorbents and coagulants, pH, and initial concentration of boron. Therefore, this review sought to comprehensively and critically demonstrate strategic issues that may guide the choice of method and adsorbent or coagulant material in future research for bench and industrial scale boron removal.

Boron contamination and its risk management in terrestrial and aquatic environmental settings

Boron (B) is released to terrestrial and aquatic environments through both natural and anthropogenic sources. This review describes the current knowledge on B contamination in soil and aquatic environments in relation to its geogenic and anthropogenic sources, biogeochemistry, environmental and human health impacts, remediation approaches, and regulatory practices. The common naturally occurring sources of B include borosilicate minerals, volcanic eruptions, geothermal and groundwater streams, and marine water. Boron is extensively used to manufacture fiberglass, thermal-resistant borosilicate glass and porcelain, cleaning detergents, vitreous enamels, weedicides, fertilizers, and B-based steel for nuclear shields. Anthropogenic sources of B released into the environment include wastewater for irrigation, B fertilizer application, and waste from mining and processing industries. Boron is an essential element for plant nutrition and is taken up mainly as boric acid molecules. Although B deficiency in agricultural soils has been observed, B toxicity can inhibit plant growth in soils under arid and semiarid regions. High B intake by humans can be detrimental to the stomach, liver, kidneys and brain, and eventually results in death. Amelioration of soils and water sources enriched with B can be achieved by immobilization, leaching, adsorption, phytoremediation, reverse osmosis, and nanofiltration. The development of cost-effective technologies for B removal from B-rich irrigation water including electrodialysis and electrocoagulation techniques is likely to help control the predominant anthropogenic input of B to the soil. Future research initiatives for the sustainable remediation of B contamination using advanced technologies in soil and water environments are also recommended.

Selective Removal of Boron from Aqueous Solutions Using ECH@NGM Aerogels with Excellent Hydrophilic and Mechanical Properties: Performance and Response Surface Methodology Analysis

The remediation of environmental boron contamination has received extensive research attention. The adsorbent ECH@NGM aerogel with high hydrophilic and mechanical properties was synthesized to remove boron. The ECH@NGM aerogel had a high adsorption capacity of 81.11 mg/g, which was 14.50% higher than that of commercial boron-selective resin Amberlite IRA743. The Freundlich model and pseudo-second-order model described the adsorption behavior well. In addition, the response surface methodology (RSM) could predict the experimental outcomes and optimize the reaction conditions, and X-ray photoelectron spectroscopy (XPS) and control tests were utilized to investigate probable adsorption mechanisms. These data showed that the B ← N coordination bond was the primary adsorption force. The adsorbent had good resistance to interference from coexisting salts, high reusability, good adsorption performance even after five reuse cycles, and a high desorption rate in a relatively short time. The adsorption performance in real brines could be maintained at 80%. Therefore, this work not only provided ECH@NGM aerogels for the removal of boron from brine but also elucidated the main adsorption processes between N-containing adsorbents and boron, facilitating the design of future adsorbents for boron removal.

Advances in Technologies for Boron Removal from Water: A Comprehensive Review

Boron overabundance in aquatic environment raises severe concerns about the environment and human health because it is toxic to various crops and induces many human and animal diseases with long-term consequences. In response to the boron pollution of water resources and the difficulty of eliminating boron from water for production and living purposes, this article summarizes the progress in research on boron removal technology, addressing the following aspects: (1) the reasons for the difficulty of removing boron from water (boron chemistry); (2) ecological/biological toxicity and established regulations; (3) analysis of different existing processes (membrane processes, resin, adsorption, chemical precipitation, (electric) coagulation, extraction, and combined methods) in terms of their mechanisms, effectiveness, and limitations; (4) prospects for future studies and possible improvements in applicability and recyclability. The focus of this paper is thus to provide a comprehensive summary of reported deboronation processes to date, which will definitely identify directions for the development of boron removal technology in the future.

A review of boron removal from aqueous solution using carbon-based materials: An assessment of health risks

Carbon-based compounds have gained attention of researchers for use in boron removal due to their properties, which make them a viable and low cost adsorbent with a high availability, as well as environmental friendliness and high removal efficiency. The removal of boron utilizing carbon-based materials, including activated carbon (AC), graphene oxide (GO), and carbon nanotubes (CNTs), is extensively reviewed in this paper. The effects of the operating conditions, kinetics, isotherm models, and removal methods are also elaborated. The impact of the modification of the lifetime of carbon-based materials has also been explored. Compared to unmodified carbon-based materials, modified materials have a significantly higher boron adsorption capability. It has been observed that adding various elements to carbon-based materials improves their surface area, functional groups, and pore volume. Tartaric acid, one of these doped elements, has been employed to successfully improve the boron removal and adsorption capabilities of materials. An assessment of the health risk posed to humans by boron in treated water utilizing carbon-based materials was performed to better understand the performance of materials in real-world applications. Furthermore, the boron removal effectiveness of carbon-based materials was evaluated, as well as any shortcomings, future perspectives, and gaps in the literature.

Cellulose-derived polyols as high-capacity adsorbents for rapid boron and organic pollutants removal from water

Excess boron in water could result in a critical hazard to plants and humans. Traditional treatment approaches cannot efficiently remove boron from water, especially during seawater desalination using reverse osmosis technology. Achieving satisfactory adsorption capacity and rate for boron remains an unmet goal for decades. Herein, we report cellulose-derived polyols as high-performance adsorbents that can rapidly remove boron and organic pollutants from water. Cellulose-derived polyols were synthesized from saccharides and cellulose via controlled radical polymerization and click reaction. Remarkably, CA@NMDG can adsorb boron with an astonishing capacity of ~34 mg g^-1 in 10 min, which surpasses all those cellulose-based materials reported thus far, meanwhile, much faster than those of commercial adsorption resin. Moreover, cellulose-derived polyols also showed high removal efficiencies (70-98% in several minutes) toward certain organic pollutants, including Congo red and Reactive Blue 19. The water-insoluble characteristic of cellulose-derived polyols is advantageous to be separated from the treated sewage after adsorption for reuse. This work provides a novel insight into the fabrication of safe, fast, and high-capacity cellulose adsorbents for water purification.

Hierarchical porous biochar from plant-based biomass through selectively removing lignin carbon from biochar for enhanced removal of toluene

This study proposed a simple and green air oxidation (AO) method to prepare hierarchical porous biochar by selectively removing lignin carbon from biochar after the pyrolysis of plant-based biomass, based on the fact that the thermal decomposition temperature in air between lignin carbon and cellulose/hemicellulose carbon was different. Three kinds of biomass with different lignocellulose contents were used, including walnut shell, cypress sawdust and rice straw. The results found that AO treatment could effectively improve the pore structure of the three biochar. The specific surface area of WCO-4, CCO-4 and RCO-4 was 555.0 m²/g, 418.7 m²/g and 291.9 m²/g, respectively, which was significantly higher than those of WC (319.5 m²/g), CC (381.7 m²/g) and RC (69.6 m²/g), respectively. Among these, walnut shell biochar with air oxidation (WCO) had higher surface area of 555.0 m²/g and mesopore volume of 0.116 cm³/g, this was related to its high content of lignin, which could facilitate the formation of mesopores by AO treatment with high selectivity. The toluene adsorption capacity of WCO reached 132.9 mg/g, which increased by 223.4% from that without AO treatment. The kinetics study indicated that the diffusion rates of toluene molecule were improved due to the increased mesopores volume of biochar and micropores also play an important role in the adsorption of toluene. The results demonstrate that AO treatment is a promising method to develop hierarchical porous structure for lignocellulose-rich plant-based biomass with low cost and environmental-friendly, which greatly enhanced the toluene adsorption capacity.

Recent advances in adsorption and coagulation for boron removal from wastewater: A comprehensive review

The anthropogenic emission of boron to river has become a serious problem that deteriorates the water quality and endangers the ecosystem. Although boron is a micronutrient, it is toxic to plants, animals and humans upon exposure. In this review, we first present the sources of the boron-containing streams and their composition, and then summarize the recent progress of boron removal methods based on adsorption and coagulation systematically. The boron-spiked streams are produced from coal-fired and geothermal power plants, the manufacturing and the activities of oil/gas excavation and mining. The adsorbents for boron removal are classified into the ones functionalized by chelating groups, the ones on the basis of clays or metal oxide. Three subgroups reside in the coagulation approach: electrocoagulation, chemical precipitation and chemical oxo-precipitation. The hybrid technology that combines membrane process and adsorption/coagulation was covered as well. To provide a comprehensive view of each method, we addressed the reaction mechanism, specified the strength and weakness and summarized the progress in the past 5 years. Ultimately, the prospective for future research and the possible improvement on applicability and recyclability were proposed.

A functionalized bio-based material with abundant mesopores and catechol groups for efficient removal of boron

Pursuing a low-cost yet sustainable material with a high performance of removing boron is necessary for replacement of the synthetic adsorbents, but remains challengeable. Herein, we fabricated an mesopore-dominated bio-based material (LS-CPAM-TA) with abundant catechol groups by the electrostatic-interaction-driven self-assembly of lignosulfonate (LS), tannic acid (TA) and cationic polyacrylamide (CPAM) for efficient removal of boron. LS-CPAM-TA presented a mesopore area of 53.9 m²/g with a mesoporous distribution of 2-25 nm, as well as a mesopore/micropore volume ratio of 129.7. Such a mesopore-rich feature not only promoted the exposure of catechol groups in TA, which served as the adsorption sites, but also contributed to enhance the fast mass transport of boron. Consequently, a maximum adsorption capacity of 119.05 mg/g was observed for LS-CPAM-TA, surpassing some reported adsorbents. Even for the low concentration boron, LS-CPAM-TA also displayd the high adsorption efficiency. Moreover, LS-CPAM-TA followed the Langmuir isotherm adsorption model, and presented the excellent regeneration performance due to its robust self-assembled structure driven by the electrostatic interaction among LS, CPAM and TA. This work would provide guidelines for target design of bio-based materials with tunable porous structure and versatile adsorption or catalytic sites for various applications.

Cyclodextrin derivatives used for the separation of boron and the removal of organic pollutants

Adsorption plays an important role in seawater desalination, wastewater treatment, and, especially, boron removal from natural aqueous systems. In this paper, two sponge-like multifunctional polymers based on a cyclodextrin backbone were synthesized and used as adsorbents for the removal of boron, methylene blue (MB), methyl orange (MO), and phenol. The syntheses were carried out by esterification, atom transfer polymerization, and nucleophilic addition reaction. The polymers were characterized by ¹H NMR spectroscopy, IR spectroscopy, XRD, XPS, and SEM. The performance of the two different adsorbents was investigated considering the effect of pH, initial concentration, and the anions and cations in an aqueous solution of borates. The experimental data were fitted with an adsorption isothermal model, adsorption kinetic model and other models. Both adsorbents exhibited high adsorption capacities (B: 31.05 mg/g and 20.45 mg/g, MB: 29.43 mg/g and 32.29 mg/g, MO: 47.36 mg/g and 49.23 mg/g, phenol: 5.04 mg/g and 4.35 mg/g, respectively) and a fast adsorption rate. The boron adsorption was found to be an exothermic process. The adsorbents show promising potential for the removal of boron and benzene-containing organic pollutants from aqueous solution.

Utilization of edible fungi residues towards synthesis of high-performance porous carbon for effective sorption of Cl-VOCs

Edible fungi residues are natural fungi etching feedstock that provide loose structure with multidimensional framework. These advantages help KOH to penetrate rigid cytoderm into innermost space and attain porous carbon with high porosity. Utilization of edible fungi residue not only avoids artificial operation of fungal inoculation and culture steps, but also provides new method for waste disposal. As expected, carbon derived from three fungi residues attains excellent porosity. The highest surface area reaches 3463.3 m²/g, which is approximately 2 and 6 times higher than original biomass (1630.7 m²/g) and commercial carbon (691.1 m²/g), respectively. Filiform structures derived from hyphae growth contribute to pores formation. Coprinus comatus fungi residue as optimal raw material obtains hierarchical pore channel with dominant micropores (76%) and natural nitrogen doping (1.28 at.%). The highest DCM and CB adsorption capacities attain 716.9 and 641.7 mg/g, respectively, which are 13 and 6 times higher than that of commercial carbon. The positive effects from fungi growth improve DCM adsorption particularly. DCM adsorption over fungi residues derived carbon is twice higher than original biomass carbon. Competitive adsorption, recyclability, surface variations and desorption components after saturated adsorption are fully investigated for practical application. The present study provides a new insight for developing high-value technology for synthesizing Cl-VOCs adsorbents using edible fungi residues.

Boron incorporation into precipitated calcium carbonates affected by aqueous pH and boron concentration

The objectives of this study were to investigate the amount of B incorporation into precipitated calcium carbonate (PCC) in the coprecipitation process, and to determine specific mineral phases (calcite or vaterite) and the mode of B coordination (trigonal or tetrahedral) in PCC under different pH and B concentrations. The amount of B incorporation into PCC increased in general with increasing aqueous B (B_aq) concentrations in the pH range from 8 to 12. The B removal by PCC reached maximum (∼200 mmol kg^-1) at pH 10 with B_aq concentrations between 30 and 50 mM. The transformation of vaterite to calcite was promoted with increasing B_aq at pH 8 and 10, whereas an excess concentration of aqueous (poly)borate anions (100 mM) inhibited crystal growth of calcite. As determined by B K-edge X-ray absorption fine structure spectroscopy, the coordination of B incorporated in PCC was preferentially tetrahedral (^IVB, 55-70%) over trigonal (^IIIB, 30-45%) at B_aq <75 mM. In contrast, the preferential incorporation of ^IVB into PCC was not observed in the solution with a high B concentration (i.e., 100 mM). The amount of B incorporation, the morphology of PCC and B coordination in PCC were remarkably changed in high B_aq concentrations.

Thermal and pH dual-responsive cellulose microfilament spheres for dye removal in single and binary systems

Cellulose microfilaments/poly(N-Isopropylacrylamide-co-acrylic acid) spheres (MPNAA) were prepared via the in-situ synthesis of semi-interpenetrating networks (semi-IPN). The free radical copolymerization of acrylic acid (AA) (for pH-sensitive chain segments) and N-isopropylacrylamide (NIPAM) (for temperature-sensitive chain segments) was conducted in a microwave-reactor in the presence of porous cellulose/microfilament composite spherical beads pre-prepared. The surface morphology and adsorption properties of the as-prepared spheres were systematically characterized. The adsorption behaviors of resulting MPNAA towards dyes, methylene blue (MB) and methyl violet (MV), were pH sensitive; and the optimal adsorption occurred at pH 9. The dynamic adsorption processes could be well fitted with pseudo-second-order kinetic, Elovich and simplified intraparticle diffusion models. Meanwhile, Langmuir, Temkin, Freundlich, and Dubinin-Raduskevich models were used to fit the adsorption isotherms at 25, 40, and 55 °C, respectively. The results indicated that the adsorption capacities of MPNAA towards MB and MV could reach as high as 497.5 and 840.3 mg g^-1, respectively, in single systems; and high adsorption capacity was maintain in binary systems with the favorable adsorption of MV. Overall, the semi-IPN MPNAA spheres are promising as novel pH- and temperature-responsive adsorbents, facilitating the controllable adsorption/desorption processes.

Three-dimensional porous graphene oxide-maize amylopectin composites with controllable pore-sizes and good adsorption-desorption properties: Facile fabrication and reutilization, and the adsorption mechanism

Three-dimensional (3D) porous graphene oxide-maize amylopectin (GO-MA) composites with controllable pore-sizes composites in the range of 6-40 nm were prepared by facile hydrothermal-assisted assembly approaches. The morphologies, pore sizes, specific surface area (SSA) and compositions of GO-MA_x:y composites with and different GO-to-MA mass ratios (x:y) were characterized by scanning electron microscopy (SEM), N₂ adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). To reveal the adsorption-desorption mechanism, effects of contact time, temperature, initial adsorbate concentration, pH value of the solution on the adsorption process were studied in detail. The adsorption capacities of 3D GO-MA_20:1 composite for organic contaminants including tert-butyl hydroquinone (TBHQ), p-aminophenol (PAP), p-nitrophenol (PNP), o-nitrophenol (MNP), hydroquinone (HQ), alizarin red S (ARS) and neutral red (NR) were 22.17, 116.4, 44.78, 36.96, 16.10, 39.92 and 24.23 mg g^-1, respectively. The adsorption capacities of GO-MA_30:1 composite for inorganic substances including Pb²⁺, Mn²⁺, Cr₂O₇^2-, Cd²⁺, Cu²⁺, Nd³⁺, La³⁺, Y³⁺, Yb³⁺ and Er³⁺ were 84.76, 7.92, 13.6, 17.64, 30.56, 25.52, 12.48, 16.96, 23.32 and 30.32 mg g^-1, respectively. In addition, GO-MA_x:y composites also exhibited high mechanical properties and good reusability. Consequently, GO-MA_x:y composites could be used as reusable adsorbents for removal/enrichment inorganic/organic substances in aqueous solutions.

Microbial Targeted Degradation Pretreatment: A Novel Approach to Preparation of Activated Carbon with Specific Hierarchical Porous Structures, High Surface Areas, and Satisfactory Toluene Adsorption Performance

Hierarchical porous carbon shows great potential for volatile organic compounds (VOCs) removal due to its high surface area and abundant porous framework. However, current fabrication protocols are complex and cause secondary pollution, limiting their application. Here, as a novel strategy, microbial lignocellulose decomposition as a pretreatment was introduced to fabricate hierarchical porous carbon (M-AC) from crude biomass substrate. The M-AC samples had high specific surface areas (maximum: 2290 m²·g^-1) and surfaces characterized by needle-like protrusions with a high degree of disorder attributed to hierarchical porous structures. Dynamic toluene adsorption indicated that the carbon materials with microbial pretreatment had much better adsorption performances (maximum: 446 mg/g) than activated carbon without pretreatment. The M-AC material pretreated with a cellulose-degrading microbe showed the best adsorption capacity due to well-developed micropores, whereas the M-AC material pretreated with a lignin-degrading microbe showed excellent transport diffusion due to well-developed mesopores. Therefore, this simple and effective approach using microbial decomposition pretreatment is promising for the development of hierarchical porous carbons with adjustable pore structures and high specific surface areas to remove target VOCs in practical applications.