One-pot Pyrolysis Research Articles

Agar-derived nitrogen-doped porous carbon as anode for construction of cost-effective lithium-ion batteries

Balancing cost and performance of porous carbon (PC) as anode for lithium-ion battery (LIBs) is the key to effectively promote commercial application. Herein, low-cost N-doped PC (NPC-Ts, T = 600, 750 and 900 °C) were facilely prepared in batches via one-pot pyrolysis of agar with different carbonization temperature. The NPC-750 with specific surface area of 2914 m2/g and N content of 2.84% exhibits an ultrahigh reversible capacity of 1019 mAh/g at 0.1 A/g after 100 cycles and 837 mAh/g at 1 A/g after 500 cycles. Remarkably, the resulting LIBs exhibit an ultrafast charge-discharge feature with a remarkable capacity of 281 mAh/g at 10 A/g and a superlong cycle life with a capacity retention of 87% after 5000 cycles at 10 A/g. Coupling with LiFePO4 cathode, the fabricated lithium-ion full cells possess high capacity, excellent rate and cycling performances (125 mAh/g at 100 mA/g, capacity retention of 95%, after 220 cycles), highlighting the practicability of this NPC-750 as the anode materials.

Renal clearing carbon dots-based near-infrared fluorescent super-small nanoprobe for renal imaging

Real-time renal imaging is indispensable for monitoring kidney-related disease processes and evaluating the nephrotoxicity of nanoprobes. Owing to their small size, tunable photoluminescence properties, and low biotoxicity, carbon dots (CDs) are widely employed as nanoprobes for imaging-guided disease diagnosis. However, the preparation of near-infrared CDs is a stupendous challenging. Here, CDs with near-infrared fluorescence (NIR-CDs) were prepared by one-pot pyrolysis and were comprehensively evaluated for real-time renal imaging. The NIR-CDs possessed super-small size (1.8 ± 0.2 nm) and high quantum yield (14.3% in aqueous solution) at 696 nm. NIR-CDs exhibited high-efficiency renal clearance at 24 h post-treatment (97.47–99.27% ID) via glomerular filtration. The irreversible clearance of NIR-CDs enables effective real-time monitoring of kidney function in the normal and acute kidney injury (AKI) mouse models. Consequently, NIR-CDs can be utilized for imaging analyses of impaired kidney function, pioneering a serviceable guideline for neoapplications of NIR-CDs.

Nano-architecture of MOF (ZIF-67)-based Co3O4 NPs@N-doped porous carbon polyhedral nanocomposites for oxidative degradation of antibiotic sulfamethoxazole from wastewater

Co3O4 NPs in N-doped porous carbon (Co3O4 NPs@N-PC) materials were prepared by one-pot pyrolysis of a ZIF-67 powder under N2 atmosphere and followed by oxidation under air atmosphere (200 °C) toward promotion catalytic activity and activation of peroxymonosulfate (PMS) to degradation sulfamethoxazole (SMZ). 2-methylimidazole was used as a nitrogen source and a competitive ligand for the synthesis of Co3O4 NPs@N-PC, which in addition to affecting nucleation and growth of the crystal, promotes the production of active Co–N sites. Co3O4 NPs@N-PC nano-architecture has high specific surface areas (250 m2 g−1) and is a non-toxic, effective and stable PMS activator. The effect of operating parameters including SMZ concentration, catalyst dosage, temperature and pH in the presence of Co3O4 NPs@N-PC was investigated. The Co3O4 NPs@N-PC composite showed superior performance in activating PMS over a wide range of pH (2–10) and different temperatures so that complete degradation of SMZ (50 μM, 100 mL) was achieved within 15 min. The role of Co2+/Co3+ redox system in the mechanism before and after PMS activation was determined using XPS analysis. Surface-generated radicals led to the degradation of SMZ, in which the SMZ degradation rate attained 0.21 min−1 with the mineralization of 36.8%. The feasible degradation mechanism of SMZ was studied in the presence of different scavengers and it was revealed that the degradation reaction proceeds from the radical/non-radical pathway and in this process most of the SO4− and OH radicals are dominant. The recoverability and reuse of Co3O4 NPs@N-PC were evaluated to confirm its stability and potential for SMZ degradation and it was observed that the catalyst maintains its catalytic power for at least 5 cycles.

Green synthesis of novel Fe nanoparticles embedded in N-doped biochar composites derived from bagasse for sulfadiazine degradation via peroxymonosulfate activator: Mechanism insight and performance assessment

To realize the effective utilization of agricultural and industrial waste, waste bagasse was designed to remove antibiotics from wastewater. In this work, using waste bagasse, extremely little iron resource and melamine as raw material, Fe species nanoparticles encapsulated in nitrogen-doped composite biochar derived from bagasse (Fe@NC-BS) were synthesized via a one-pot pyrolysis method. Fe@NC-BS-8 has the advantages of high catalytic activity, magnetic recovery, and superior stability. Surprisingly, Fe@NC-BS-8 maintained excellent anti-interference ability in wide pH range (pH = 3–11) and high concentration of coexisting anions. Surface-bound ROS (SO4- and OH) and singlet oxygen (1O2) were considered the main reactive oxygen species. Both the generation of active sites and the characteristic of composite materials were beneficial to the activation of PMS and accelerating electronic transfer. Pyridine N, graphitic N, iron species, CNTs and ketone groups were all the main active sites and showed synergistic effects. This work provided a feasible strategy for utilizing bagasse waste in a valuable manner and simultaneously achieving environmental remediation.

Efficient removal of aqueous Cr(VI) with ferrous sulfide/N-doped biochar composites: Facile, in-situ preparation and Cr(VI) uptake performance and mechanism.

FeS nanoparticles loaded on nitrogen-doped biochar (FeS/BNC) were fabricated by pyrolyzing coffee husks pretreated with Mohr's salt. The nitrogen doping and FeS loading of biochar are simultaneously achieved in one-pot pyrolysis. The elemental analysis, SEM, TEM, XRD, XPS, Raman, FTIR and N2 adsorption-desorption technologies were used to characterize the composition and structure of FeS/NBC. The appraisement for removing aqueous Cr(VI) testified that FeS/NBC offered a synergistic scavenging effect of Cr(VI) by FeS and NBC. The effect of crucial experimental conditions (FeS/NBC dosage, foreign ions, initial pH and concentration of Cr(VI) solution) were investigated. The Cr(VI) removal capacity was as high as 211.3 ± 26 mg g-1 under the optimized condition. The practicability of FeS/NBC was examined by using simulated actual samples from tap water and lake water. The mechanism examination showed that surface adsorption/reduction and solution reduction were implicated in the removal of Cr(VI). The current work introduces a novel FeS/NBC composite prepared by an in situ pyrolysis method with excellent potential for chromium pollution remediation.

Selective CO2 Electroreduction to Ethanol over a Carbon-Coated CuOx Catalyst.

The design of efficient copper(Cu)-based catalysts is critical for CO2 electroreduction into multiple carbon products. However, most Cu-based catalysts are favorable for ethylene production while selective production of ethanol with high Faradaic efficiency and current density still remains a great challenge. Herein, we design a carbon-coated CuOx (CuOx @C) catalyst through one-pot pyrolysis of Cu-based metal-organic framework (MOF), which exhibits high selectivity for CO2 electroreduction to ethanol with Faradaic efficiency of 46 %. Impressively, the partial current density of ethanol reaches 166 mA cm-2 , which is higher than that of most reported catalysts. Operando Raman spectra indicate that the carbon coating can efficiently stabilize Cu+ species under CO2 electroreduction conditions, which promotes the C-C coupling step. Density functional theory (DFT) calculations reveal that the carbon layer can tune the key intermediate *HOCCH goes the hydrogenation pathway toward ethanol production.

Co1-xS/Co3S4@N,S-co-doped agaric-derived porous carbon composites for high-performance supercapacitors

In recent years, pseudocapacitive transition metal sulfur compounds have received extensive attention as supercapacitor materials owing to their superior intrinsic conductivity. However, developing ideal structures that undergo fast Faraday redox reactions with ultra-long-term cycling performance is an important challenge. Using a homogeneous extract from agaric acid as a carbon source, a one-pot hydrothermal-assisted pyrolysis method was employed to prepare cobalt sulfide compounds. The results showed that Co1-xS/Co9S8 was generated without the addition of carbon source, while Co1-xS/Co3S4 was generated by the addition of agaric base. The prepared N,S-co-doped agaric-derived porous carbon (NSAC) nanocomposite that was densely decorated with (Co1-xS/Co3S4) to give a heterostructure(Co1-xS/Co3S4@NSAC). Co1-xS/Co3S4@NSAC exhibited high specific capacitance, as well as excellent rate capability and cycling stability performance (497.5 F g−1 at 0.5 A g−1, 96 F g−1 at 80 A g−1, with 96.9% capacity retention at 25 A g−1 for 6000 cycles). Symmetrical supercapacitors were fabricated using Co1-xS/Co3S4@NSAC, affording high energy density (17.7 Wh kg−1 at 598.9 W kg−1) and cycling retention (109% capacity retention at 5 A g−1 for 4000 cycles). Based on the experimental results and density functional theory (DFT) calculations, the Co1-xS/Co3S4 heterojunction interface allows for highly reversible and efficient electrochemical redox processes, with fast charge transfer kinetics and structural stability during the electrochemical reactions.

분무열분해 단일공정을 통한 리튬이온전지 음극소재용 MoO3 나노분말

MoO₃ nanopowders having an average size of 150 nm as anode materials for lithium ion batteries were synthesized by one-pot spray pyrolysis process. During the spray pyrolysis process, concentration difference in a droplet occurred due to the high flow rate of the carrier gas, which induced hollow intermediate powders. The intermediate hollow powders are composed of MoO_x and C, and subsequently they are decomposed into MoO₃ nanopowders without C under oxidation atmosphere. When MoO₃ nanopowders were used as anode materials, the cell showed reversible discharge capacity of 390 mA h g-¹ at a current density of 1.0 A g^-1 even after 1,000 cycles. The overwhelming cycle stability of the cell is attributed to the MoO₃ nanopowders with 150 nm that act as an effective anode material by shortening the diffusion length of Li ions to the electrode and increasing the contact surface with the electrolyte during cycles.

Fluorescent Carbon Quantum Dots Functionalized by Poly L-Lysine: Efficient Material for Antibacterial, Bioimaging and Antiangiogenesis Applications.

This study illustrates the synthesis of functionalized carbon quantum dots (CQDs) by the one-pot pyrolysis method. The functionalization agent used in CQD synthesis was poly l- lysine (PLL). Various physicochemical techniques were employed to confirm the successful formation of PLLCQD including High resolution transmission electron microscopy (HR-TEM), UV-Vis spectroscopy, fluorescence spectroscopy; Atomic force microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The size of PLLCQD was confirmed by HRTEM and AFM. The synthesized PLLCQD shows bright blue fluorescence and has a quantum yield of 19.35%. The highest emission band was observed at 471nm when excited to 370nm. The prepared PLLCQD exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus with inhibition zone 7-20 mm. The concentrations of 0.9 to 0.1gmL-1 were studied to determine minimum inhibitory concentration (MIC) by the agar well diffusion assay method. MIC of 0.2gml -1 concentration of PLLCQD is achieved. The anti-angiogenic activity of PLLCQD was determined using (Chick Chorioallantoic Membrane) CAM assay. CAM assay is a reliable in -vivo model to study angiogenesis also; many stimulators and inhibitors have been examined by this method. This study proves higher antibacterial efficiency of PLLCQD over non functionalized CQD. PLLCQD was successfully employed in bio-imaging of the bacterial cell through fluorescence microscopy. Further, PLLCQD displayed cytotoxic effect on endothelial cells and inhibited blood vessel formation in the CAM model.

Resource utilization of tannery sludge to prepare biochar as persulfate activators for highly efficient degradation of tetracycline

In this work, a low-cost carbon-based catalyst (TSBC) was prepared by the facile one-pot pyrolysis of tannery sludge (TS) and used to activate persulfate (PS) for tetracycline (TC) removal. The results showed that TSBC-500 exhibited optimal physicochemical properties and the best performance for PS activation to remove TC from drinking water. Approximately 99.1% of TC was removed in the TSBC-500/PS system, which was considerably higher than those in the TSBC-500 adsorption and pure PS systems. Radical quenching experiments indicated that •OH and SO4•- played major roles in the TC removal in the TSBC-500/PS system. In addition, transition metals, functional groups, and the high degree of carbon structural defects were beneficial for PS activation to degrade TC. This study not only newly contributes to high-value utilization of TS as a PS activator but also offers an efficient method for the removal of organic pollutants.

Porous structure engineering of N-doped carbons for enhanced mass transfer towards High-Performance supercapacitors and Li-Ion batteries

Tailoring the porous structure of carbon materials is one essential approach to improve the energy storage performance of carbon-based electrode materials. Herein, hierarchical porous carbons (HPCs) with different meso-structure are synthesized via a one-pot pyrolysis process with SiO2 and ZnCl2 as template and activator, respectively. The energy storage capacities of the obtained HPC samples are investigated as bi-functional electrode both for supercapacitor and LIBs. The results show that different meso-structure of HPCs can effectively affect the energy storage performance. In the range of 15 ∼ 50 nm, smaller size of mesopore can result better electrochemical performance of HPCs. And the optimized HPC sample (HPC-15) manifests high specific capacitance of 432F g−1 and good cyclic stability in the supercapacitor application. When used as anode of LIBs, the HPC-15 presents a high capacity of 820 mAh g−1. In addition, COMSOL simulation is employed to study the effect of pore structure on mass transfer during electrochemical process. The HPC-15 is calculated to have the highest total porosity (εp) and effective diffusivity of K+ (De = 6.776 × 10-10 m2 s−1), thus leading to its best electrochemical performance.

Carbon coated electric arc furnace dust prepared by one-pot pyrolysis: An efficient, low carbon footprint electrode material for lithium-ion batteries

This work offers useful insights into the evaluation of the electric arc furnace dust in green energy applications by surface engineering. To produce low-carbon-footprint electrodes, for the first time in the open literature, the practical pyrolysis (of sucrose) method is applied to create a nanometer-thick carbon layer over the dust. Advanced techniques are used to characterize the carbon-coated electric arc furnace flue dust morphologically, structurally, and chemically. Galvanostatic tests reveal that the carbon-coated dust exhibits 600 mAh g−1 discharge capacity after 250 cycles. The rate test proves that the carbon-coated dust can withstand a high current load (2A g−1) and delivers 540 mAh g−1 after 250 cycles when the current load is decreased to 0.1A g−1. This obtained capacity shows that with the correct material selection and process design, it is possible to produce low-carbon footprint electrodes at a low cost. Electrochemical characterizations indicate that the lithiation reaction of the carbon-coated dust takes place similarly to that of the anode materials which are made of synthetically fabricated carbon-coated transition metal oxides and/or ferrites. It is anticipated that this study sets an example for the valorization of the various industrial wastes in energy applications in the future.

Constructing single-atomic nickel sites in carbon nanotubes for efficient CO2 electroreduction

Electrochemical CO2 reduction (ECR) has been considered as the most promising route to convert CO2 into fuels, but suffers inferior conversion efficiency and product selectivity due to the lack of effective electrocatalysts. Herein, the N-coordinated single-atomic Ni active sites embedded in porous carbon nanotubes (Ni/N-CNTs) are constructed through one-pot pyrolysis strategy as an efficient ECR electrocatalyst. The Zn source in pyrolysis plays a key role in the formation of bamboo-like CNTs, and increased concentrations of surface defects and single-atomic Ni sites of the electrocatalyst. All these benefits endow the electrocatalyst with excellent ECR performance, achieving a large CO Faradaic efficiency (FECO) up to 98% and turnover frequency up to 304.5 h−1 at a relatively low potential of −0.65 V vs. RHE. Furthermore, over 80% FECO can be maintained in a wide potential range from −0.57 to −0.81 V. In addition, the electrocatalyst also shows high operation stability for 20 h without obvious FECO and jCO decay. We believe this study will shed a new light on the design of highly efficient M/N–C catalyst for ECR systems.

Catalytic cycloaddition of CO2 to epoxides by the synergistic effect of acidity and alkalinity in a functionalized biochar

Cycloaddition of CO2 to epoxides is an efficient way for CO2 fixation and recycling. Currently, the mainly used metal-containing homogeneous catalysts and halide co-catalysts for cycloaddition of CO2 could bring out metal leaching problem, which is harmful to the environment. Herein, we propose a facile way to prepare nitrogen and oxygen-rich porous biochar by one-pot pyrolysis of chitosan under CO2 atmosphere, and demonstrate the high performance of the obtained metal-free carbon material catalyst with plenty of Lewis base sites and Lewis acid sites on cycloaddition of CO2 to epoxides. The doped nitrogen and oxygen show a synergistic effect for this addition reaction, and the catalytic efficiency can be enhanced through tuning the content of nitrogen and oxygen. The yield and selectivity of epichlorohydrin (ECH) can reach to 90% and 97% with no solvents or co-catalysts under relatively mild reaction conditions, respectively. Materials characterizations and theory calculation results suggested that the high catalytic performance of the N,O-codoped porous biochar was ascribed to its excellent adsorption of CO2 and epoxide molecules due to its high specific surface area and consequent activation by its integrated acid–base active sites. This work illustrates a new strategy for recycling CO2 by using it as a pyrolytic agent and a feedstock for the synthesis of cyclic carbonates.

Chromium(VI) removal from synthetic solution using novel zero-valent iron biochar composites derived from iron-rich sludge via one-pot synthesis

In this study, Fe-rich sludge obtained from coagulation–flocculation of swine wastewater was processed into zero-valent iron (ZVI) biochar composites through one-pot pyrolysis at 700 °C under anoxic (MBCN700) and hypoxic (MBCA700) conditions. X-ray diffraction analysis revealed that α-Fe0 and γ-Fe0 were the dominant Fe species in MBCN700 and MBCA700, respectively. The effects of different process parameters, including composite dosage, initial Cr(VI) concentration, pH, dissolved O2 (DO), and contact time on Cr(VI) removal from synthetic solutions were evaluated. The results showed that both the acidic initial pH and DO contributed to Cr(VI) removal; the highest removal rate was observed at pH 3. Based on the Langmuir isotherm model, the predicted maximum removal capacity of MBCA700 was greater than that of MBCN700, primarily because of its core-shell structure, less corrosive ZVI, and higher degree of graphitization. X-ray photoelectron spectroscopy analysis coupled with fitting of the kinetic (pseudo-second-order) and isothermal (Freundlich) data suggested that Cr(VI) removal by MBCN700 occurred via adsorption, FeC micro-electrolysis, and co-precipitation. In contrast, the removal mechanism for MBCA700 included adsorption, reduction, and electrostatic attraction. Thus, ZVI biochar composites can serve as potential remediators of Cr(VI)-contaminated wastewater.

One-pot spray pyrolysis for core–shell structured Sn@SiOC anode nanocomposites that yield stable cycling in lithium-ion batteries

A novel strategy is reported for the synthesis of high-capacity anode materials with good cycling stability for use in lithium-ion batteries. A facile one-pot spray pyrolysis process is conducted using an ethanol solution of Sn acetate and diphenylsilanediol (DPSD). Phase separation between Sn and DPSD leads to the formation of core@shell-structured Sn@DPSD nanoparticles, and subsequent heat-treatment in an inert atmosphere carbonizes the DPSD to form Sn@SiOC nanoparticles (∼50 nm). When applied as an anode material in lithium-ion batteries (LIBs), the Sn core retains its high energy density, while the SiOC shell limits volume expansion of the core and protects it from pulverization and agglomeration. The Sn@SiOC nanoparticles exhibit a reversible capacity of 917 mA h g −1 at 0.1C and stable cycling performance for 200 cycles at 1C. The nanoparticle formation mechanism is investigated by optimizing the Sn acetate/DPSD ratio in the precursor solution, and the origin of the enhanced properties is investigated by comparing the results of Sn@SiOC nanoparticles with those of SiOC nanoparticles and Sn microspheres. SiOC shows considerable promise as a coating material for Sn nanoparticles, which may serve as a milestone in the synthesis of nanosized electrode materials with coatings that can prolong the cycle lives of rechargeable batteries.

Multigraphene Prepared by One-Pot Pyrolysis of Diatomite/Polypropylene Composites

Multigraphene was prepared via a one-pot pyrolysis method using polypropylene (PP) as the carbon source and diatomite (DM) as the catalyst. The obtained graphene had 4–6 layers and a D/G intensity ratio of 0.70 and a 2D/G intensity ratio of 0.72, indicating a high degree of graphitization. When the pyrolysis temperature was higher than 850 °C under argon, the graphene yield was greatly dependent on the DM content. The highest graphene yield of 25.86% was obtained by pyrolysis of PP with 30 wt.% DM at the temperature of 1000 °C. A catalytic effect of DM and infusible cross-linking structure formation were proposed to explain the possible mechanism of graphene growth during the pyrolysis of the DM/PP composites.

Highly porous structured Sr-doped La2NiO4/NiO composite cathode with interconnected pores for lithium-oxygen batteries

• Highly porous OP-SLNO was prepared by one-pot spray pyrolysis. • OP-SLNO showed improved catalytic abilities for both OER and ORR. • OP-SLNO with interconnected pores was suitably applied to Li-O 2 batteries. • Interconnected pores provided space to accommodate abundant discharge products. One-pot spray pyrolysis process is a promising continuous process for mass production of nanostructured powder. The highly porous microspheres containing pores interconnected from the inner to the outer side of particle are prepared by one-pot spray pyrolysis process. In this study, Sr-doped layered perovskite oxide is selected as the first target material. A colloid comprising mono-sized spherical templates were used as a precursor to synthesize the porous Sr-doped La 2 NiO 4 /NiO composite powder. The fine and spherical templates construct a highly open and porous structure throughout the resulting particle’s inner bulk and surfaces. The fabricated powder shows improved catalytic abilities for both OER and ORR, based on the results of the RDE measurements. Owing to the open-pore structure, the overpotentials for both discharge and charge processes are lowered attributing to extremely improved cycle life of over 180 cycles when applied to Li-O 2 cell, while the filled-structured powder gives less than 50 cycles. Furthermore, the Li-O 2 cell reveals definitely improved discharge capacity of 13,130 mA h g −1 under 200 mA g −1 owing to the interconnected pore structure, when compared to discharge capacities of closed-pores-containing powder (9,547 mA h g −1 ) and filled-structured powder (7,541 mA h g −1 ).

Plasma induced Fe-NX active sites to improve the oxygen reduction reaction performance

Rational design of high-efficient and low-cost catalysts as alternatives to Pt-based catalysts toward the oxygen reduction reaction (ORR) is extremely desirable but challenging. In this work, Fe@NCNT is firstly synthesized via the one-pot pyrolysis method, then Fe-NX active species are in-situ created on the prepared Fe@NCNT by a feasible “plasma inducing” strategy to synthesize the resulting catalyst (Fe@NCNT-P) for ORR. The morphology of Fe@NCNT-P is perfectly inherited by the derived carbon precursor, resulting in the core-shell structure of carbon-coated Fe and a mesoporous dominant nanostructure with a high specific surface area of 536 m2 g−1. The resultant Fe@NCNT-P catalyst exhibits remarkable ORR activity and durability, as well as outstanding performance in assembled zinc-air battery (ZAB) test with a peak power density of 240 mW cm−2. This work not only reports a novel and robust ORR catalyst, but also proposes a simple and effective strategy to improve the ORR electrocatalytic performance.

Simultaneous immobilization of arsenic, lead and cadmium by magnesium-aluminum modified biochar in mining soil

Owing to the human activities such as smelting and mining, arsenic (As), lead (Pb) and cadmium (Cd) seriously polluted the soil of non-ferrous metal mining areas, thus efficient methods for the simultaneous immobilization of the three heavy metals are urgently needed. In the present study, Mg–Al modified biochars (MABs) were synthesized through a simple one-pot pyrolysis method to immobilize the three heavy metals. According to the BET (Brunauer-Emmett-Teller) test method, MABs had larger specific surface areas than biochar. Compared to the materials obtained at 300 °C and 700 °C, MAB with a pyrolysis temperature of 500 °C (MAB 500) had a significant immobilization effect on As, Pb and Cd in the Gansu mining area. Compared with BC, the removal efficiencies of As, Pb and Cd increased from −62%, 17% and 5% to 52%, 100% and 66%, respectively. And the toxicity characteristic leaching procedure (TCLP) test showed that the leaching concentrations of the three heavy metals in the treated soil were all lower than the standard value. X-ray photoelectron spectroscopy and kinetic experiments showed that there were various mechanisms in the immobilization process of the three heavy metals, and the large specific surface area and the multi-Mg/Al–OH of MABs play an important role in this process. More charges were provided by larger specific surface for ion exchange with heavy metals. In addition, larger specific surface area also provided more adsorption sites. More complex sites were provided by Mg/Al–OH to form Mg/Al–O-M then immobilize the heavy metals. In summary, the immobilization mechanism may involve electrostatic attraction, precipitation/co-precipitation, and surface complexation.