Layered double hydroxides loaded sludge biochar composite for adsorptive removal of benzotriazole and Pb(II) from aqueous solution

Resourcization of Argillaceous Limestone with Mn3O4 Modification for Efficient Adsorption of Lead, Copper, and Nickel

Argillaceous limestone (AL) is comprised of carbonate minerals and clay minerals and is widely distributed throughout the Earth's crust. However, owing to its low surface area and poorly active sites, AL has been largely neglected. Herein, manganic manganous oxide (Mn3O4) was used to modify AL by an in-situ deposition strategy through manganese chloride and alkali stepwise treatment to improve the surface area of AL and enable its utilization as an efficient adsorbent for heavy metals removal. The surface area and cation exchange capacity (CEC) were enhanced from 3.49 to 24.5 m2/g and 5.87 to 31.5 cmoL(+)/kg with modification, respectively. The maximum adsorption capacities of lead (Pb2+), copper (Cu2+), and nickel (Ni2+) ions on Mn3O4-modified argillaceous limestone (Mn3O4-AL) in mono-metal systems were 148.73, 41.30, and 60.87 mg/g, respectively. In addition, the adsorption selectivity in multi-metal systems was Pb2+ > Cu2+ > Ni2+ in order. The adsorption process conforms to the pseudo-second-order model. In the multi-metal system, the adsorption reaches equilibrium at about 360 min. The adsorption mechanisms may involve ion exchange, precipitation, electrostatic interaction, and complexation by hydroxyl groups. These results demonstrate that Mn3O4 modification realized argillaceous limestone resourcization as an ideal adsorbent. Mn3O4-modified argillaceous limestone was promising for heavy metal-polluted water and soil treatment.

Removal of benzotriazole derivatives by biochar: Potential environmental applications

Benzotriazole and its derivatives (BTAs) are commonly present in wastewater due to their extensive use in industrial processes, yet their removal is still unexplored. Here, we test the removal of these pollutants using two functionalised biochars, synthesised from wild plum (WpOH) and apricot (AsPhA) kernels. The aim of this work was to optimise the adsorption process against various BTAs (i.e., benzotriazole (BTZ), 4-hydroxy-1H-benzotriazole (OHBZ), 4-methyl-1H-benzotriazole (4 MBZ), 5-methyl-1H-benzotriazole (5 MBZ), 5-chloro-1H-benzotriazole (ClBZ), 5,6-dimethyl-1H-benzotriazole (DMBZ)), and determine the adsorption mechanisms at play, using real wastewater matrices. Batch studies showed that the optimal adsorption pH ranged between 4 and 6 for WpOH and AsPhA, respectively, and equilibrium was reached after 240 min. The kinetic models that best described the adsorption process were in the following order: Elovich model > pseudo-second order model > pseudo-first order model. The equilibrium data showed the highest correlation with the Freundlich isotherm, indicating multilayer adsorption. The maximum adsorption capacity obtained in mixtures was 379 mg/g on WpOH and 526 mg/g on AsPhA. The mechanistic work revealed that the BTAs became bound to the biochar primarily through H-bonding, n-π and π-π EDA interactions. In wastewater, obtained before and after conventional treatment, the concentration of OHBZ and BTZ was reduced by >40%, while the concentration of the other compounds studied fell below the detection limit (∼2.0-90 ng/L). Finally, using a Vibrio fischeri assay, we showed that adsorption onto AsPhA significantly reduced the relative toxicity of both raw and treated wastewater.

Potassium permanganate modification of hydrochar enhances sorption of Pb(II), Cu(II), and Cd(II)

Hydrochars formed by hydrothermal carbonization of hickory wood, bamboo, and wheat straw at 200 °C were modified by potassium permanganate (KMnO4) for the sorption of Pb(II), Cd(II), and Cu(II). The wheat straw hydrochar (WSHyC) modified with 0.2 M KMnO4 resulted in the most promising adsorbent (WSHyC-0.2KMnO4). Characterization of WSHyC and WSHyC-0.2KMnO4 revealed that the modified hydrochar features large specific surface area, rich of surface oxygenic functional groups (OCFG), and a significant amount of MnOx micro-particles. Batch adsorption experiments indicated that the adsorption rate by WSHyC-0.2KMnO4 was faster than for WSHyC, attaining equilibrium after around 5 h. The optimum adsorption capacity (Langmuir) of Pb(II), Cd(II), and Cu(II) by WSHyC-0.2KMnO4 was 189.24, 29.06 and 32.68 mg/g, respectively, 12 ∼ 17 times greater than by WSHyC. The significantly enhanced heavy metal adsorption can be attributable to the increased OCFG and MnOx microparticles on the surface, thereby promoting ion exchange, electrostatic interactions, and complexation mechanisms.

Effective adsorption of Pb(ii) from wastewater using MnO2 loaded MgFe-LD(H)O composites: adsorption behavior and mechanism

Pb(ii) adsorption by MnO₂/MgFe-layered double hydroxide (MnO₂/MgFe-LDH) and MnO₂/MgFe-layered metal oxide (MnO₂/MgFe-LDO) materials was experimentally studied in lab-scale batches for remediation property and mechanism analysis. Based on our results, the optimum adsorption capacity for Pb(ii) was achieved at the calcination temperature of 400 °C for MnO₂/MgFe-LDH. Langmuir and Freundlich adsorption isotherm models, pseudo-first-order and pseudo-second-order kinetics, Elovich model, and thermodynamic studies were used for exploring the Pb(ii) adsorption mechanism of the two composites. In contrast to MnO₂/MgFe-LDH, MnO₂/MgFe-LDO_{400 °C} has a stronger adsorption capacity and the Freundlich adsorption isotherm model (R² > 0.948), the pseudo-second-order kinetic model (R² > 0.998), and the Elovich model (R² > 0.950) provide great fits to the experimental data, indicating that the adsorption occurs predominantly via chemisorption. The thermodynamic model suggests that MnO₂/MgFe-LDO_{400 °C} is spontaneously heat-absorbing during the adsorption process. The maximum adsorption capacity of MnO₂/MgFe-LDO_{400 °C} for Pb(ii) was 531.86 mg g^-1 at a dosage of 1.0 g L^-1, pH of 5.0, and temperature of 25 °C. Through characterization analysis, the main mechanisms involved in the adsorption process were precipitation action, complexation with functional groups, electrostatic attraction, cation exchange and isomorphic replacement, and memory effect. Besides, MnO₂/MgFe-LDO_{400 °C} has excellent regeneration ability in five adsorption/desorption experiments. The above results highlight the powerful adsorption capacity of MnO₂/MgFe-LDO_{400 °C} and may inspire the development of new types of nanostructured adsorbents for wastewater remediation.

Efficient Adsorption Capacity of MgFe-Layered Double Hydroxide Loaded on Pomelo Peel Biochar for Cd (II) from Aqueous Solutions: Adsorption Behaviour and Mechanism

A novel pomelo peel biochar/MgFe-layered double hydroxide composite (PPBC/MgFe-LDH) was synthesised using a facile coprecipitation approach and applied to remove cadmium ions (Cd (II)). The adsorption isotherm demonstrated that the Cd (II) adsorption by the PPBC/MgFe-LDH composite fit the Langmuir model well, and the adsorption behaviour was a monolayer chemisorption. The maximum adsorption capacity of Cd (II) was determined to be 448.961 (±12.3) mg·g^-1 from the Langmuir model, which was close to the actual experimental adsorption capacity 448.302 (±1.41) mg·g^-1. The results also demonstrated that the chemical adsorption controlled the rate of reaction in the Cd (II) adsorption process of PPBC/MgFe-LDH. Piecewise fitting of the intra-particle diffusion model revealed multi-linearity during the adsorption process. Through associative characterization analysis, the adsorption mechanism of Cd (II) of PPBC/MgFe-LDH involved (i) hydroxide formation or carbonate precipitation; (ii) an isomorphic substitution of Fe (III) by Cd (II); (iii) surface complexation of Cd (II) by functional groups (-OH); and (iv) electrostatic attraction. The PPBC/MgFe-LDH composite demonstrated great potential for removing Cd (II) from wastewater, with the advantages of facile synthesis and excellent adsorption capacity.

One-pot preparation of layered double oxides-engineered biochar for the sustained removal of tetracycline in water

Tetracycline (TC) and sugarcane bagasse had both exerted enormous strain on environmental security. In this work, new composite adsorbent designed by impregnating bio-waste bagasse with magnesium-aluminum layered double oxides (BC-MA) was innovatively brought forward for TC removal. Benefiting from the abundant adsorption sites supplied by developed pores structure (0.308 cm³·g^-1), enlarged surface area (256.8 m²·g^-1) and reinforced functional groups, the maximum adsorption amount of BC-MA for TC reached 250.6 mg g^-1. Moreover, BC-MA displayed desirable adsorption capacity in diverse water environments coupled with excellent sustainable regeneration ability. The absorption process of TC by BC-MA was spontaneous and endothermic, and the pivotal rate-limiting stage pertained to intraparticle diffusion. The mechanisms proposed here mainly concerned π-π interactions, pore filling, complexation and hydrogen bonding. These findings suggested that the synthesis of modified biochar from bagasse would offer new opportunities for simultaneous waste resource reuse and water pollution control.

Simultaneous immobilization of arsenic, lead, and cadmium in soil by magnesium-aluminum modified biochar: Influences of organic acids, aging, and rainfall

Magnesium-aluminum modified biochar (MABs) has an outstanding effect on the simultaneous immobilization of arsenic (As), lead (Pb), and cadmium (Cd) in soil, but the stability of remediation effect of MAB under various natural conditions is still unknown. In this study, we investigated the effects of organic acids, dry-wet cycles (DW), freeze-thaw cycles (FT), and rainfall (pH 4, 7, and 8) on the immobilization of As, Pb, and Cd by MAB. The results showed that oxalic acid decreased the immobilization efficiencies of As, Pb, and Cd by 15.5%-38.5%; meanwhile, humic acid reduced the immobilization efficiency of Pb by 89.7%, but elevated that of Cd by 19.5%. The immobilization mechanisms of MAB-5 on three metals were mainly involved in ion exchange and surface-complexation. Compared with the 7th round, the immobilization efficiencies of As, Pb, and Cd by MAB in the 28th round was decreased by 17%-28% in DW, but was increased by 11%-18% in FT. In addition, MAB was transformed into hydrotalcite after FT and DW. After experiencing simulated rainfall, MAB caused more As, Pb, and Cd to be retained in the upper soil layer, and the immobilization effect of MBA was more significant under the stimulated rainfall with higher pH. The study provides a more theoretical basis for the application of MAB in the actual site remediation.

Synthesizing biochar-based slow-releasing fertilizers using vermicompost leachate, cow dung, and plant weed biomass

Biochar-based slow-releasing fertilizers (BSRF) have been recommended widely for efficient soil nutrient management and crop production. In this study, we examined the N, P, and K release behaviour of pyrolysed (at 350 °C) cow dung (CDB), vermicompost (VCB), and Lantana (LB) weed and impregnated LB (LBVW) and CDB (CDBVW) with vermicompost leachate (1:1 v/v) under a lab-scale trial. BSRFs (CDB, VCB, LBVW and VCBVW) characterization (FT-IR, SEM-EDX and surface area analysis) was done and then tested for its suitability for soil-plant applications. Soil incubation study indicated the slow-releasing behaviour of BSRFs and overall P, N, and K release was found to be in the ranges of 72.3-84.5%, 73.1-79.0%, and 43.1-85.3%, respectively in different BSRFs setups. Furthermore, lab trials suggested the highest P (64.5%), N (75.3%), and K (86.8%) uptakes by the plant (Vigna radiata) in CDBVW and LBVW setups. Moreover, pot trails with moong bean (Vigna radiata) suggested a high growth in shoot and root and plant yield as well in seedlings cultivated with BSRFs. This study indicates that animal manure, vermicompost and terrestrial weed Lantana biochar can be used effectively to prepare BSRFs for efficient soil-plant nutrient management with multiple environmental benefits.

Assessment in carbon-based layered double hydroxides for water and wastewater: Application of artificial intelligence and recent progress

Layered double hydroxides (LDHs) are a class of clays with brucite like layers and intercalated anions. Hybrids of carbon nanomaterials and layered double hydroxides (C-LDHs) are promising nanomaterials due to their versatile properties and the large number of composition/preparation variables available for fine-tuning. Several techniques are available for the synthesis of these novel C-LDHs nanocomposites. This article assess developments in the synthesis and applications of C-LDHs in water and wastewater treatment via using artificial intelligence approaches. In addition, current challenges and possible strategies are discussed from the viewpoint of synthesis and application. It is concluded that the use of C-LDH is expected to produce interesting results. The anisotropic properties and good dispersion ability make them suitable to be used as particulates in the dispersion phase of electro-responsive and electro-rheological fluids. Although these materials have been tested for the removal of contaminants from single component solutions in water. In addition, application of artificial intelligence in this regard is discussed. At the end, the necessity of evaluating their performance in the removal of contaminants from multi-components solutions is proposed. Finally the challenges in obtaining material with precisely controlled particle sizes and morphology must be addressed.

Layered double hydroxides functionalized by carbonaceous materials: from preparation to energy and environmental applications

Along with the exponential demand for energy and pollution-free-environment, layered double hydroxides (LDHs) have gained extensive explorations because of their diverse nanostructures and tunable elemental compositions. However, the applications of LDHs are hindered by their poor activity, sluggish mass transfer, and aggregation. LDHs functionalized by carbonaceous materials (CMs) (LDH-CM) are expected to overcome the above disadvantages and even generate more excellent performance. This review first analyzes the research evolvement of LDH-CM composites during the past 25 years. Next, the advantages of LDH-CM composites are highlighted, such as morphology optimization, high electrical conductivity, more stable, good heat, and mass transfer performance. Following the synthetic strategies, including chemical assembly of LDHs and CMs, direct growth of LDH on CMs (two-step nucleation and growth and surface-confined growth) and direct CM formation on LDHs are fully discussed. Then, the recent progress achieved in LDH-CM composites for the application of energy storage and environmental protection is summarized in detail. In particular, the review illustrates the reasons why these constructing strategies can improve the performance of LDH-CM composites. Finally, challenges and future research prospects of LDH-CM composites are highlighted.

Exploring the Adsorption of Pb on Microalgae-Derived Biochar: A Versatile Material for Environmental Remediation and Electroanalytical Applications

Biochar, a carbon material obtained by pyrolysis of biomasses, is increasingly applied in environmental remediation and sensing thanks to its functional properties, cost-effectiveness and eco-friendliness. The adsorption capacity of biochar, strictly dependent on its specific surface area, heteroatom doping and surface functional groups, is crucial for these applications. Here, biochar produced at low temperature (350 °C) from a marine microalga (Nannochloropsis sp.) is proposed as an efficient adsorbent of lead (II) ions in aqueous solution; this production strategy promotes the natural self-doping of biochar without requiring harsh conditions. The kinetics and thermodynamics of the adsorption process, as well as the effect of pH, ionic strength and dissolved organic matter on the adsorption efficiency were systematically assessed. The microalgae-derived biochar shows superior adsorption performances compared to a nutshell-derived one (used as a reference of lignocellulosic feedstocks) under all the tested conditions. The microalgae-derived biochar was finally used to decorate screen-printed carbon electrodes to improve the electroanalytical performances towards the voltammetric detection of lead (II) ions. A two-fold increase in sensitivity was obtained compared to the unmodified electrode thanks to the enhanced electron transfer and adsorption properties provided by biochar. These results highlight the potentialities of microalgae-derived biochar for environmental and sensing applications.

A Comprehensive Review of Layered Double Hydroxide-Based Carbon Composites as an Environmental Multifunctional Material for Wastewater Treatment

As is well known, hydrotalcite-like compounds, such as layered-double-hydroxide (LDH) materials, have shown great potential applications in many fields owing to their unique characteristics, including a higher anion exchange capacity, a structure memory effect, low costs, and remarkable recyclability. While the lower surface area and leaching of metal ions from LDH composites reduce the process efficiency of the catalyst, combining LDH materials with other materials can improve the surface properties of the composites and enhance the catalytic performance. Among organic compounds, carbon materials can be used as synergistic materials to overcome the defects of LDHs and provide better performance for environmental functional materials, including adsorption materials, electrode materials, photocatalytic materials, and separation materials. Therefore, this article comprehensively reviews recent works on the preparation and application of layered double-hydroxide-based carbon (LDH–C) composites as synergistic materials in the field of environmental remediation. In addition, their corresponding mechanisms are discussed in depth. Finally, some perspectives are proposed for further research directions on exploring efficient and low-cost clay composite materials.

Electrospun polyacrylonitrile/hydroxyapatite composite nanofibrous membranes for the removal of lead ions from aqueous solutions

A novel Polyacrylonitrile/Hydroxyapatite (PAN/HAP) composite nanofibrous membranes were successfully prepared via the electrospinning approach. The scanning electron microscope, Fourier transforms infrared, X-ray diffraction were selected to serve as characterization techniques...