Microwave assisted green synthesis of Fe2O3/biochar for ultrasonic removal of nonsteroidal anti-inflammatory pharmaceuticals

Iron oxide/biochar (Fe₂O₃/biochar) was prepared by green synthesis via a microwave to evaluate ultrasound-assisted adsorption capacity of Nonsteroidal Anti-inflammatory Drugs (NSAIDs) (salicylic acid, naproxen, and ketoprofen) from the water. Several techniques of characterization, including, Fourier transform infrared spectrometry, scanning electron microscopy, EDS analysis, N₂ adsorption–desorption, X-ray diffraction, and Raman spectrometry were applied. The adsorption of NSAIDs onto Fe₂O₃/biochar was performed using an ultrasonic bath. The effects of batch adsorption under various experimental parameters such as contact time (0–120 min), initial concentration (10–500 mg L⁻¹) and pH (2–12) were tested. The obtained Fe₂O₃/biochar specific surface area, mesopore volume/micropore volume, and pores size were equal to 786 m² g⁻¹, 0.409 cm³ g⁻¹, and 1.534 cm³ g⁻¹, respectively. The pseudo-second-order model could describe better all NSAID adsorptions onto Fe₂O₃/biochar. The Langmuir model agreed well with the NSAID adsorptions and the maximum adsorption capacities reached 683 mg g⁻¹, 533 mg g⁻¹ and 444 mg g⁻¹ for salicylic acid, naproxen, and ketoprofen, respectively. Fe₂O₃/biochar can be used as an excellent adsorbent for the treatment of NSAIDs in water.

Here, we have developed a simple and green microwave synthesis of iron oxide/biochar for the removal of new emergent pharmaceutical pollutants.     

Simultaneous removal of Sb(iii) and Cd(ii) in water by adsorption onto a MnFe2O4–biochar nanocomposite

In this study, a jacobsite–biochar nanocomposite (MnFe₂O₄–BC) was fabricated and used to simultaneously remove Sb(iii) and Cd(ii) from water via adsorption. The MnFe₂O₄–BC nanocomposite was prepared via a co-precipitation method and analyzed using various techniques. The results confirm the successful decoration of the biochar surface with MnFe₂O₄ nanoparticles. The maximum Sb(iii) removal efficiency was found to be higher from bi-solute solutions containing Cd(ii) than from single-solute systems, suggesting that the presence of Cd(ii) enhances the removal of Sb(iii). The Langmuir isotherm model describes well Sb(iii) and Cd(ii) removal via adsorption onto the MnFe₂O₄–BC nanocomposite. The maximum adsorption capacities are 237.53 and 181.49 mg g⁻¹ for Sb(iii) and Cd(ii), respectively, in a bi-solute system. Thus, the prepared MnFe₂O₄–BC nanocomposite is demonstrated to be a potential adsorbent for simultaneously removing Sb(iii) and Cd(ii) ions from aqueous solutions.

In this study, a jacobsite–biochar nanocomposite (MnFe₂O₄–BC) was fabricated and used to simultaneously remove Sb(iii) and Cd(ii) from water via adsorption.     

Single-step synthesis of eucalyptus sawdust magnetic activated carbon and its adsorption behavior for methylene blue

Eucalyptus wood-based magnetic activated carbon (MAC) was prepared using single-step carbonization activation magnetization with FeCl₃ and utilized for the adsorption of methylene blue (MB). The MAC was prepared using the following conditions: the mass ratio of FeCl₃ to eucalyptus sawdust was controlled to 2 : 1, the one-step carbonated activated magnetization temperature and time was 700 °C and 75 min. The prepared MAC was evaluated for textural characteristics such as the adsorption capacity, pore structure, surface chemical functional groups, magnetic properties, microcrystalline structure, and the surface morphology using the test methods described in the National Standard of China, these were N₂-adsorption–desorption isotherms, Fourier transform infrared spectroscopy (FTIR), value stream mapping (VSM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Batch experiments were carried out to evaluate the adsorption behavior of MB on the prepared MAC at different temperatures of 298–328 K and MB initial concentration of 50.0–500.0 mg L⁻¹. The results were as follows: the iodine number, methylene blue adsorption and phenol adsorption of the prepared MAC were 473.14, 228.22 and 70.90 mg g⁻¹, respectively; MAC exhibited a microporous and mesoporous structure with a mesoporosity of 36%, the BET specific surface area, average pore diameter and pore volume were 645.23 m² g⁻¹, 2.71 nm and 0.44 cm³ g⁻¹, respectively, and for the magnetic parameters the following results were found, a H_c of 108.51 Oe, M_s of 30.37 emu g⁻¹ and M_r of 2.46 emu g⁻¹; there were OH, C–O, C O, C C, COO, C–N, and Fe–O groups on the MAC surface, and Fe₃O₄ existed in the pores and surfaces of the MAC. The MB adsorption on the MAC followed the Langmuir isotherm and Dubinin–Radushkevich isotherm model, the adsorption process was a spontaneous, endothermic chemisorption progress, followed by the pseudo-second-order model, and the adsorption process was influenced by multiple diffusion steps, the pore diffusion process was the rate-controlling step, however, the adsorption process was also affected by the film diffusion and surface adsorption. The results reveal that MAC efficiently adsorbs MB and can be easily separated and recovered by an external magnetic field. The as-prepared MAC could be used as a potential adsorbent for organic pollutant wastewater treatment.

Eucalyptus wood-based magnetic activated carbon (MAC) was prepared by single-step carbonization activation magnetization with FeCl₃ and utilized for the adsorption of methylene blue (MB).     

Environmental surface chemistries and adsorption behaviors of metal cations (Fe3+, Fe2+, Ca2+ and Zn2+) on manganese dioxide-modified green biochar

The facile preparation and modification of low-cost/efficient adsorbents or biochar (CP) derived from the carbonization of palm kernel cake (lignocellulosic residue) has been studied for the selective adsorption of various metal cations, such as Fe³⁺, Fe²⁺, Ca²⁺ and Zn²⁺, from aqueous solution. The CP surface was modified with KMnO₄ (CPMn) and HNO₃ (CPHNO₃) in order to improve the adsorption efficiency. The physicochemical properties of the as-prepared adsorbents were investigated via BET, pH_pzc, FT-IR, Boehm titration, TG-DTG, XRD and SEM-EDS techniques. The surfaces of all adsorbents clearly demonstrated negative charge (pH_pzc > pH of the mixture solution), resulting in a high adsorption capacity for each metal cation. Fe²⁺ was found to be more easily adsorbed on modified CP than the other kinds of metal cations. Synergistic effects between the carboxylic groups and MnO₂ on the surface of CPMn resulted in better performance for metal cation adsorption than was shown by CPHNO₃. The maximum adsorption capacities for Fe³⁺, Fe²⁺, Ca²⁺ and Zn²⁺ using CPMn, which were obtained from a monolayer adsorption process via Langmuir isotherms (R² > 0.99), were 70.67, 68.60, 5.06 and 22.38 mg g⁻¹, respectively. The adsorption behavior and monolayer-physisorption behavior, via a rapid adsorption process as well as single-step intra-particle diffusion, were also verified and supported using Dubinin–Radushkevich, Redlich–Peterson and Toth isotherms, a pseudo-second-order kinetic model and the Weber–Morris model. Moreover, the thermodynamic results indicated that the adsorption process of metal cations onto the CPMn surface was endothermic and spontaneous in nature. This research is expected to provide a green way for the production of low-cost/efficient adsorbents and to help gain an understanding of the adsorption behavior/process for the selective removal of metal ions from wastewater pollution.

Manganese dioxide-modified green biochar exhibited excellent capacity for adsorption of Fe³⁺, Fe²⁺, Ca²⁺ and/or Zn²⁺.     

Enhanced phosphate sequestration by Fe(iii) modified biochar derived from coconut shell

In this work, a novel Fe-modified coconut shell biochar (Fe-CSB) was synthesized and utilized to remove phosphate from aqueous solution. Characterization results confirmed that the iron in the Fe(iii)-impregnated CSB existed mainly in the amorphous phase, as ferrihydrite and amorphous hydroxide, which substantially enhanced the phosphate adsorption. Batch experiments indicated that phosphate adsorption on the Fe-CSB was highly dependent on the pH, the humic acid, and temperature, while it was less affected by the nitrate. Phosphate adsorption by the CSB and Fe-CSB could be well described by the pseudo n-th order and Langmuir–Freundlich models. The fitting of the experimental data with the intra-particle diffusion model revealed that surface adsorption and inner-sphere diffusion were involved in the phosphate adsorption process, and that the latter was the rate-controlling step. Batch adsorption experiments and post-adsorption characterization results revealed that the phosphate adsorption by Fe-CSB was primarily governed by four mechanisms: ligand exchange, electrostatic attraction, chemical precipitation, and inner-sphere complexation. This work demonstrated that the modified Fe-CSB is an environmentally friendly and cost-effective bioretention medium and could open up new pathways for the removal of phosphorus from stormwater, as well as solve the problem of waste biomass pollution.

In this work, a novel Fe-modified coconut shell biochar (Fe-CSB) was synthesized and utilized to remove phosphate from aqueous solution.     

Novel easily separable core–shell Fe3O4/PVP/ZIF-8 nanostructure adsorbent: optimization of phosphorus removal from Fosfomycin pharmaceutical wastewater

A new easily separable core–shell Fe₃O₄/PVP/ZIF-8 nanostructure adsorbent was synthesized and then examined for removal of Fosfomycin antibiotic from synthetic pharmaceutical wastewater. The removal process of Fosfomycin was expressed through testing the total phosphorus (TP). A response surface model (RSM) for Fosfomycin adsorption (as mg-P L⁻¹) was used by carrying out the experiments using a central composite design. The adsorption model showed that Fosfomycin adsorption is directly proportional to core–shell Fe₃O₄/PVP/ZIF-8 nanostructure adsorbent dosage and time, and indirectly to initial Fosfomycin concentration. The removal increased by decreasing the pH to 2. The Fosfomycin removal was done at room temperature under an orbital agitation speed of 250 rpm. The adsorption capacity of core–shell Fe₃O₄/PVP/ZIF-8 nanostructure adsorbent reached around 1200 mg-P g⁻¹, which is significantly higher than other MOF adsorbents reported in the literature. The maximum Langmuir adsorption capacity of the adsorbent for Fosfomycin was 126.58 mg g⁻¹ and Fosfomycin adsorption behavior followed the Freundlich isotherm (R² = 0.9505) in the present study. The kinetics was best fitted by the pseudo-second-order model (R² = 0.9764). The RSM model was used for the adsorption process in different target modes.

The synthesis of an easily separable novel core–shell Fe₃O₄/PVP/ZIF-8 nanostructure adsorbent and its usage for Fosfomycin pharmaceutical wastewater treatment.     

In situ fabrication of hierarchical biomass carbon-supported Cu@CuO–Al2O3 composite materials: synthesis,properties and adsorption applications

Hierarchical Cu–Al₂O₃/biomass-activated carbon composites were successfully prepared by entrapping a biomass-activated carbon powder derived from green algae in the Cu–Al₂O₃ frame (H–Cu–Al/BC) for the removal of ammonium nitrogen (NH₄⁺-N) from aqueous solutions. The as-synthesized samples were characterized via XRD, SEM, BET and FTIR spectroscopy. The BET specific surface area of the synthesized H–Cu–Al/BC increased from 175.4 m² g⁻¹ to 302.3 m² g⁻¹ upon the incorporation of the Cu–Al oxide nanoparticles in the BC surface channels. The experimental data indicated that the adsorption isotherms were well described by the Langmuir equilibrium isotherm equation and the adsorption kinetics of NH₄⁺-N obeyed the pseudo-second-order kinetic model. The static maximum adsorption capacity of NH₄⁺-N on H–Cu–Al/BC was 81.54 mg g⁻¹, which was significantly higher than those of raw BC and H–Al/BC. In addition, the presence of K⁺, Na⁺, Ca²⁺, and Mg²⁺ ions had no significant impact on the NH₄⁺-N adsorption, but the presence of Al³⁺ and humic acid (NOM) obviously affected and inhibited the NH₄⁺-N adsorption. The thermodynamic analyses indicated that the adsorption process was endothermic and spontaneous in nature. H–Cu–Al/BC exhibited removal efficiency of more than 80% even after five consecutive cycles according to the recycle studies. These findings suggest that H–Cu–Al/BC can serve as a promising adsorbent for the removal of NH₄⁺-N from aqueous solutions.

Hierarchical Cu–Al₂O₃/biomass-activated carbon composites were successfully prepared by entrapping a biomass-activated carbon powder derived from green algae in the Cu–Al₂O₃ frame (H–Cu–Al/BC) for the removal of ammonium nitrogen (NH₄⁺-N) from aqueous solutions.     

Acid–base sites synergistic catalysis over Mg–Zr–Al mixed metal oxide toward synthesis of diethyl carbonate

In heterogeneous catalysis processes, development of high-performance acid–base sites synergistic catalysis has drawn increasing attention. In this work, we prepared Mg/Zr/Al mixed metal oxides (denoted as Mg₂Zr_xAl_1−x–MMO) derived from Mg–Zr–Al layered double hydroxides (LDHs) precursors. Their catalytic performance toward the synthesis of diethyl carbonate (DEC) from urea and ethanol was studied in detail, and the highest catalytic activity was obtained over the Mg₂Zr_0.53Al_0.47MMO catalyst (DEC yield: 37.6%). By establishing correlation between the catalytic performance and Lewis acid–base sites measured by NH₃-TPD and CO₂-TPD, it is found that both weak acid site and medium strength base site contribute to the overall yield of DEC, which demonstrates an acid–base synergistic catalysis in this reaction. In addition, in situ Fourier transform infrared spectroscopy (in situ FTIR) measurements reveal that the Lewis base site activates ethanol to give ethoxide species; while Lewis acid site facilitates the activated adsorption of urea and the intermediate ethyl carbamate (EC). Therefore, this work provides an effective method for the preparation of tunable acid–base catalysts based on LDHs precursor approach, which can be potentially used in cooperative acid–base catalysis reaction.

Mg/Zr/Al mixed metal oxides were prepared via a facile phase transformation process of hydrotalcite precursors, which showed acid–base sites synergistic catalytic performance toward the synthesis of diethyl carbonate from ethanol and urea.     

Quantification and isotherm modelling of competitive phosphate and silicate adsorption onto micro-sized granular ferric hydroxide

Adsorption onto ferric hydroxide is a known method to reach very low residual phosphate concentrations. Silicate is omnipresent in surface and industrial waters and reduces the adsorption capacity of ferric hydroxides. The present article focusses on the influences of silicate concentration and contact time on the adsorption of phosphate to a micro-sized iron hydroxide adsorbent (μGFH) and fits adsorption data to multi-component adsorption isotherms. In Berlin drinking water (DOC of approx. 4 mg L⁻¹) at pH 7.0, loadings of 24 mg g⁻¹ P (with 3 mg L⁻¹ initial PO₄³⁻–P) and 17 mg L⁻¹ Si (with 9 mg L⁻¹ initial Si) were reached. In deionized water, phosphate shows a high percentage of reversible bonds to μGFH while silicate adsorption is not reversible probably due to polymerization. Depending on the initial silicate concentration, phosphate loadings are reduced by 27, 33 and 47% (for equilibrium concentrations of 1.5 mg L⁻¹) for 9, 14 and 22 mg L⁻¹ Si respectively. Out of eight tested multi-component adsorption models, the Extended Freundlich Model Isotherm (EFMI) describes the simultaneous adsorption of phosphate and silicate best. Thus, providing the means to predict and control phosphate removal. Longer contact times of the adsorbent with silicate prior to addition of phosphate reduce phosphate adsorption significantly. Compared to 7 days of contact with silicate (c₀ = 10 mg L⁻¹) prior to phosphate (c₀ = 3 mg L⁻¹) addition, 28 and 56 days reduce the μGFH capacity for phosphate by 21 and 43%, respectively.

Adsorption of phosphate onto ferric hydroxide in complex waters is influenced by effects of competition, displacement and surface blockage.     

Functionalized biochar-supported magnetic MnFe2O4 nanocomposite for the removal of Pb(ii) and Cd(ii)

In this study, a novel magnetic biochar-MnFe₂O₄ nanocomposite (BC/FM) was prepared using low-cost corn straw and MnFe₂O₄ by sol–gel/pyrolyzing route using egg white, which has abundant functional groups (–NH₂ and –COOH). Following that, its composition, morphology and structure was characterized by various techniques including SEM-EDX, BET, XRD, and VSM. Batch experiment of the adsorption for Pb(ii) and Cd(ii) including influence of pH, kinetics, isotherm and thermodynamics was also studied. The results demonstrated that biochar could effectively support MnFe₂O₄, which displayed high dispersion on the surface of the biochar and possessed abundant functional groups and high surface area contributing to superior performance on Pb(ii) and Cd(ii) removal. Therein, MnFe₂O₄ with high magnetism is convenient for separating the magnetic BC/FM from an aqueous medium. Adsorption experiment results indicate that Pb(ii) and Cd(ii) removal by BC/FM was closely related to pH with the best value of pH 5.0, and the process reached equilibrium in 2 h. The adsorption process is well-described by the pseudo-second-order kinetic model and Sips (Freundlich–Langmuir) model. Thermodynamic studies suggest that the adsorption process is spontaneous and exothermic. The maximum experimental adsorption capacity of BC/FM is 154.94 and 127.83 mg g⁻¹ for Pb(ii) and Cd(ii), respectively, in single-solute system, which is higher than that of some of the other adsorbents of biochar or biochar-based composites. In bi-solute system, the preferential adsorption order of BC/FM for the two metals is Pb(ii) prior to Cd(ii). Finally, FTIR and XPS analysis verified that the main mechanism of Pb(ii) and Cd(ii) removal by BC/FM is by forming Pb/Cd–O or complexation of carboxyl and hydroxyl and ion exchange. Therefore, the prepared magnetic BC/FM composite, as an excellent adsorbent, exhibited potential applications for the removal of Pb(ii) and Cd(ii) from wastewater.

In this study, a novel magnetic biochar-MnFe₂O₄ nanocomposite (BC/FM) was prepared using low-cost corn straw and MnFe₂O₄ by sol–gel/pyrolyzing route using egg white, which has abundant functional groups (–NH₂ and –COOH).     

Antibiotic removal by agricultural waste biochars with different forms of iron oxide

Pollution by antibiotics has become a serious threat to public health. In this study, agricultural waste, corn husk, in the form of biochar, was utilized for antibiotic removal from wastewater. Two kinds of iron-loaded biochars, impregnation–pyrolysis biochar (IP) and pyrolysis–impregnation biochar (PI), were synthesized to adsorb the typical antibiotics tetracycline (TC) and levofloxacin (LEV). PI contained amorphous hydrated iron oxide, whereas the major component of IP was γ-Fe₂O₃. Compared with IP, PI had a much higher adsorption capacity for both TC and LEV. This was because PI could provide more –OH, especially –OH_ads, to serve as the adsorption sites. In comparison with TC, –OH was prone to combine with LEV. FT-IR and XPS results indicated that the mechanisms of LEV adsorption included hydrogen bonding, F-replacement, electrostatic attraction and bridging bidentate complexation. TC adsorption may involve complexation, hydrogen bonding and electrostatic attraction.

The possible adsorption mechanisms.     

Single-component and competitive adsorption of tetracycline and Zn(ii) on an NH4Cl-induced magnetic ultra-fine buckwheat peel powder biochar from water: studies on the kinetics,isotherms, and mechanism

Single-component and competitive adsorption of tetracycline (TC) and Zn(ii) on an NH₄Cl-induced magnetic ultra-fine buckwheat peel powder biochar (NH₄Cl-BHP-char/Fe₃O₄) was investigated in batch experiments. NH₄Cl-BHP-char/Fe₃O₄ exhibited a large surface area of 1119.097 m² g⁻¹ and a total pore volume of 0.139 cm³ g⁻¹ and was easily separated from aqueous solution using a magnet. Also, adsorption was endothermic, spontaneous, and highly pH-dependent. The optimum pH of the single-component adsorption of TC and Zn(ii) was 4.0 and 6.5, respectively, and the optimum pH of co-adsorption was 6.0. The kinetics studies showed the prepared biochar could be rapidly adsorbed within 60 min, and chemical adsorption was dominant. For single-component adsorption, the maximum adsorption capacities of TC and Zn(ii) were 106.38 and 151.52 mg g⁻¹, respectively, and they underwent monolayer adsorption on the biochar surface. Moreover, for competitive adsorption, maximum TC and Zn(ii) adsorption capacities of 126.58 and 357.14 mg g⁻¹ were achieved. Both film diffusion and intra-particle diffusion were found to be significant processes to facilitate adsorption. TC and Zn(ii) promoted the adsorption of each other. The proposed biochar could be used repeatedly for at least four cycles. All these results demonstrated that developed NH₄Cl-BHP-char/Fe₃O₄ was regarded as a low-cost alternative adsorbent to remove the heavy metal ions and antibiotic pollutants from water or wastewater.

Single-component and competitive adsorption of tetracycline (TC) and Zn(ii) on an NH₄Cl-induced magnetic ultra-fine buckwheat peel powder biochar (NH₄Cl-BHP-char/Fe₃O₄) was investigated in batch experiments.     

Effect of SiO2 amount on heterogeneous base catalysis of SiO2@Mg–Al layered double hydroxide

The effects of SiO₂ amount on the base catalysis of highly active finely crystallized Mg–Al type layered double hydroxides prepared by the co-precipitation method with coexistence of SiO₂ spheres, denoted as SiO₂@LDHs, were investigated. With the Si/(Mg + Al) atomic ratios of 0–0.50, the highest activity for the Knoevenagel condensation was observed in the case of Si/(Mg + Al) = 0.17, as the reaction rate of 171.1 mmol g(cat)⁻¹ h⁻¹. The base activity increased concomitantly with decreasing LDH crystallite size up to Si/(Mg + Al) atomic ratio of 0.17. However, above the Si/(Mg + Al) atomic ratio of 0.17, the reaction rate and TOF_base were decreased although the total base amount was increased. Results of TEM-EDS and ²⁹Si CP-MAS NMR suggest that the co-existing SiO₂ causes advantages for dispersion and reduction of the LDH crystallite to improve the base catalysis of SiO₂@Mg–Al LDH, whereas the excess SiO₂ species unfortunately poisons the highly active sites on the finely crystallized LDH crystals above a Si/(Mg + Al) atomic ratio of 0.17. According to these results, we inferred that the amount of spherical SiO₂ seeds in the co-precipitation method is an important factor to increase the base catalysis of SiO₂@LDHs; i.e. the control of Si/(Mg + Al) atomic ratio is necessary to avoid the poisoning of highly active base sites on the LDH crystal.

The effects of SiO₂ amount on the base catalysis of highly active finely crystallized Mg–Al LDH(s) prepared by the co-precipitation method with coexistence of SiO₂ sphere seeds were investigated by XRD, ICP, ²⁹Si NMR, TEM-EDS and other techniques.     

Pyrolytic behavior of a zero-valent iron biochar composite and its Cu(ii) removal mechanism

The reduction behavior of Fe³⁺ during the preparation of a zero-valent iron cocoanut biochar (ZBC8-3) by the carbothermic reduction method was analyzed. Fe³⁺ was first converted into Fe₃O₄, which was subsequently decomposed into FeO, and finally reduced to Fe⁰. A minor amount of γ-Fe₂O₃ was produced in the process. The isothermal thermodynamic data for the removal of Cu(ii) over ZBC8-3 followed a Langmuir model. The Langmuir equation revealed a maximum removal capacity of 169.49 mg g⁻¹ at pH = 5 for ZBC8-3. The removal of Cu(ii) over ZBC8-3 fitted well to a pseudo-first-order equation, which suggested that the rate limiting step of the process was diffusion. The Cu(ii) removal mechanism on ZBC8-3 involved the reduction of Cu(ii) by Fe⁰ to produce Cu⁰ and Cu₂O, while C C, C–O–, and –O–H formed a complex with Cu(ii).

The Cu(ii) removal mechanism on ZBC8-3 involved the reduction of Cu(ii) by Fe⁰ to produce Cu⁰ and Cu₂O, while C C, C–O–, –O–H formed a complex with Cu(ii).     

Synthesis of Fe3O4@PVBC–TMT nanoparticles for the efficient removal of heavy metals ions

Core–shell magnetic Fe₃O₄@PVBC–TMT (Fe₃O₄@polyvinylbenzyl chloride–trithiocyanuric acid) nanoparticles containing trithiocyanuric acid groups were fabricated and employed for the fast removal of heavy metals from an aquatic environment. The morphology, structure and properties of Fe₃O₄@PVBC–TMT nanoparticles were characterized by a series of modern analytical tools. The adsorption behavior of the Fe₃O₄@PVBC–TMT nanoparticles for heavy metals ions in aqueous solutions was investigated by batch experiments. The maximum removal capacities of the Fe₃O₄@PVBC–TMT nanoparticles toward Mn²⁺, Ni²⁺, Cu²⁺, Cd²⁺ and Pb²⁺ ions were 127.4, 146.6, 180.5, 311.5, and 528.8 mg g⁻¹, respectively. Importantly, it is found that Pb²⁺ ions can be completely and quickly removed by the Fe₃O₄@PVBC–TMT nanoparticles. The equilibrium was established within 6 min, and the removal efficiencies were found to be 99.9%, 99.8% and 99.5% for Pb²⁺ ions at the initial concentrations of 100 mg L⁻¹, 200 mg L⁻¹ and 300 mg L⁻¹, respectively. It is hoped that the core–shell magnetic Fe₃O₄@PVBC–TMT nanoparticles may find application in wastewater treatment.

Core–shell Fe₃O₄@PVBC–TMT nanoparticles were fabricated and served as a valid magnetic adsorbent for the removal of heavy metals ions.     

Removal of methyl orange from water by Fenton oxidation of magnetic coconut-clothed biochar

Water pollution has become a serious environmental problem to date. Advanced oxidation processes (AOP) have been widely applied in water treatments. However, the traditional Fenton reaction based on the Fe²⁺–H₂O₂ system has obvious drawbacks, limiting further practical applications. In this work, an Fe₃O₄ and nano-clothed biochar (Fe₃O₄/CBc) composite was prepared through a precipitation method and used for the degradation of methyl orange (MO) in water. The Fe₃O₄/CBc composite was characterized by FTIR, BET, SEM, TEM, XRD, and VSM. In addition, the adsorption/catalytic oxidation of MO were also tested. Specifically, Fe₃O₄/CBc had a rough surface, abundant porous structure, high surface area of 835.82 m² g⁻¹, and obvious magnetization. The catalyst showed rather high performance towards MO removal. The optimal conditions for MO removal were as follows: the dosage of hydrogen peroxide was 16 mmol L⁻¹, pH = 3, the temperature was 35 °C, and the addition amount of adsorbent was 10 mg. Under optimal conditions, the MO removal rate can be higher than 99%. The synergistic effect between catalytic degradation and adsorption in removing MO was also observed. Besides high performance in removing MO, Fe₃O₄/CBc also exhibited high stability, easy magnetic separation, and great reusability, as well as the potential to be developed as a new heterogeneous Fenton catalyst.

Water pollution has become a serious environmental problem to date. Advanced oxidation processes (AOP) have been widely applied in water treatments.     

Biochar derived from corn stalk and polyethylene co-pyrolysis: characterization and Pb(ii) removal potential

Biochar is widely used as adsorbents for gaseous or liquid pollutants due to its special pore structure. Previous studies have shown that the adsorption performance of untreated biomass pyrolysis crude carbon is poor, which can be improved by optimizing physicochemical properties such as pore structure and surface area. The study focused on the co-pyrolysis of skins, pith, and leaves with polyethylene and potassium hydroxide modification to adjust the quality of the biochar, compared with raw materials of corn stalks without separation. The physical and chemical properties of the biochar were analyzed and the adsorption effect, adsorption isotherms, and kinetics of Pb(ii) removal were investigated. Results demonstrated that co-pyrolysis of biomass and polyethylene increase the yield of biochar with an average increase of about 20%. Polyethylene brought high aromaticity, high calorific value and stable material structure to biochar. Potassium hydroxide modification increased its specific surface area and made the pore structure of biochar more uniform, mainly microporous structure. The specific surface areas of the four modified biochar were 521.07 m² g⁻¹, 581.85 m² g⁻¹, 304.99 m² g⁻¹, and 429.97 m² g⁻¹. The adsorption capacity of biochar for Pb(ii) was greatly improved with the increase of the OH functional group of biochar. The stem-pith biochar had the best adsorption effect, with an adsorption amount of 99.95 mg g⁻¹ and a removal efficiency of 50.35%. The Pseudo-second-order model and Langmuir adsorption isotherm model could preferably describe the adsorption process, indicating the adsorption of lead was monolayer accompanied by chemical adsorption. It can be concluded that co-pyrolysis of biomass and polyethylene and modification may be favorable to enhance the properties of biochar. In addition to syngas and bio-oil from co-pyrolysis, biochar may be a valuable by-product for commercial use, which can be used to remove heavy metals in water, especially stem-pith biochar.

Biochar is widely used as adsorbents for gaseous or liquid pollutants due to its special pore structure.     

Electrochemical preparation and properties of a Mg–Li–Y alloy via co-reduction of Mg(ii) and Y(iii) in chloride melts

Mg–Li based alloys have been widely used in various fields. However, the widespread use of Mg–Li based alloys were restricted by their poor properties. The addition of rare earth element in Mg–Li can significantly improve the properties of alloys. In the present work, different electrochemical methods were used to investigate the electrochemical behavior of Y(iii) on the W electrode in LiCl–KCl melts and LiCl–KCl–MgCl₂ melts. In LiCl–KCl melts, typical cyclic voltammetry was used to study the electrochemical mechanism and thermodynamic parameters for the reduction of Y(iii) to metallic Y. In LiCl–KCl–MgCl₂ melts, the formation mechanism of Mg–Y intermetallic compounds was investigated, and the results showed that only one kind of Mg–Y intermetallic compound was formed under our experimental conditions. Mg–Li–Y alloys were prepared via galvanostatic electrolysis, and XRD and SEM equipped with EDS analysis were used to analyze the samples. Because of the restrictions of EDS analysis, ICP-AES was used to analyze the Li content in Mg–Li–Y alloys. The microhardness and Young''s modulus of the Mg–Li–Y alloys were then evaluated.

Mg–Li based alloys have been widely used in various fields.     

Layered zinc hydroxide as an adsorbent for phosphate removal and recovery from wastewater

At present, phosphate removal and recovery from wastewater is gaining wide attention due to the dual issues of eutrophication, caused by the increased production of algae, and universal phosphorus scarcity. In this study, a layered zinc hydroxide (LZH) was synthesized by a simple precipitation method and characterized via various techniques. Experiments investigating the effect of contact time, pH, LZH dose, initial phosphate concentration, and co-existing ions on phosphate adsorption were conducted. LZH exhibited a high phosphate adsorption capacity (135.4 mg g⁻¹) at a neutral pH. More than 50% of phosphate was removed within the first 60 s of contact time at an initial phosphate concentration of 5 mg L⁻¹. Phosphate removal using the as-prepared LZH adsorbent was also tested in real treated sewage effluent reducing the residual phosphate amount to levels inhibiting to the growth of algae. Furthermore, phosphate desorption from LZH was investigated using acetic acid and sodium hydroxide regenerants which showed to be very effective for phosphate recovery.

This study demonstrates a novel LZH adsorbent synthesized, characterized and applied for high phosphate removal and recovery from wastewater.      

Structural and adsorption characteristics of potassium carbonate activated biochar

Potassium carbonate activated biochar (450 °C, 600 °C and 750 °C) and nonactivated biochar (600 °C) were prepared by using corn stalk as the raw material. These biochar samples were labeled as KBC450, KBC600, KBC750 and BC600. The physical and chemical properties of the biochar were strongly influenced by the activation of potassium carbonate. After activation with potassium carbonate, the aromatic, hydrophobic and non-polar properties of the biochar were enhanced to form an aromatized non-polar surface, and the aromatic properties were enhanced with the increase of the pyrolysis temperature. The outside surface of the activated biochar was similar to that of porous sponge with a mesoporous–microporous composite structure inside. The specific surface area of KBC600 was 5 times that of BC600, and KBC750 had a maximum surface area of 815 m² g⁻¹. Batch adsorption experiments showed that the adsorption capacity of KBC for naphthalene increased with the increase of pyrolysis temperature. The adsorption capacity of the biochar for naphthalene showed a significant positive correlation with O/C and (O + N)/C. KBC750 with the strongest surface hydrophobicity and the largest specific surface area had the largest adsorption capacity of 130.7 mg g⁻¹. Physical adsorption and π–π EDA were the main adsorption mechanisms.

The structure activation of K₂CO₃ enriches the surface pores of biochar and increases the specific surface area nearly 10 times. The changes of pore structure and surface properties significantly affect the adsorption process of naphthalene.