Search Results (22)

Background: Traditional methods exhibit an extremely low removal efficiency for antibiotics in water, making an efficient and energy-saving approach urgently needed. Methods and Results: In this study, a novel catalytic approach based on the in situ generation of high-valent iron (Fe(IV)/Fe(V)) has been developed by adding biochar instead of modifying the electrode materials (in previous studies) for the efficient removal of sulfamethoxazole (SMX) from water. Fe(IV)/Fe(V) was produced by the anodic oxidation of low concentrations of Fe(III) and subsequently activated by nitrogen-doped corn stalk biochar (NBC). The results showed that the degradation efficiency increased from 50.83% to 90.67% within 60 min after the addition of nitrogen-modified biochar. The abundant defect structures, graphitic N and oxygen-containing functional groups in NBC endowed the catalyst with excellent activation capability. Quenching experiments and methyl phenyl sulfoxide (PMSO) probe experiments revealed that singlet oxygen (¹O₂) and Fe(IV)/Fe(V) were the main contributors to SMX degradation. Degradation pathways were inferred based on transformation products (TPs) and density functional theory (DFT) calculations. Ecotoxicity prediction using the ECOSAR program indicated that the TPs formed in the E/Fe(III)/NBC system exhibited markedly lower toxicity to aquatic organisms than the parent SMX. Furthermore, the E/Fe(III)/NBC system maintained a high degradation efficiency for SMX in real aquatic environments. Additionally, the E/Fe(III)/NBC system showed high removal rates for other sulfonamides such as sulfadiazine (SDZ), sulfamethoxypyridazine (SMP), sulfathiazole (STZ) and sulfadoxine (SDX). Conclusions: Overall, the E/Fe(III)/NBC system was demonstrated to be a highly efficient and sustainable technology for removing various antibiotics from water. Full article

Corn (Zea mays L.) ranks among the most important cereal crops globally, extensively cultivated for food, animal feed, and industrial applications. Its large-scale production generates substantial amounts of agricultural residues such as cobs, husks, stalks, leaves and other, which are often underutilized, leading to environmental concerns. Due to their high carbon content, lignocellulosic structure, and abundant availability, these residues represent a sustainable and low-cost raw material for the synthesis of activated carbon. Corn waste-derived activated carbon has emerged as a promising material for the efficient removal of heavy metals from aqueous solutions. Its high surface area, well-developed porosity, and adjustable surface chemistry, referring to the functional groups on the adsorbent surface that can be modified to enhance affinity toward metal ions, facilitate effective adsorption. This review provides a comprehensive overview of (1) the potential of corn waste biomass as a precursor for activated carbon production, (2) methods of carbonization and activation that influence the textural and chemical properties of the resulting adsorbents, (3) adsorption performance for heavy metal removal under varying experimental parameters such as pH, initial concentration, contact time, and adsorbent dosage, (4) adsorption mechanisms responsible for heavy metal uptake. Reported maximum adsorption capacities vary for different metals, ranging from 2.814–206 mg/g for lead, 0.21–87.72 mg/g for cadmium, 9.6246–175.44 mg/g for chromium, and 0.724–643.92 mg/g for copper. Utilizing corn waste not only provides an eco-friendly approach for managing agricultural residues but also supports the development of efficient adsorbents. Nevertheless, challenges such as scaling up production and evaluating adsorbent performance in real wastewater samples remain and require further investigation. Finally, the review highlights key challenges and knowledge gaps in current research and offers recommendations for future studies aimed at advancing the practical application of corn waste–based activated carbons in water treatment. Full article

Using common corn stalks as raw materials, a functional dense-structured carbon microsphere with good elastic deformation and certain rigid support was modified from biomass through a step-by-step hydrothermal method. The composition, thermal stability, fluid-loss reduction performance, and reservoir protection performance of the modified carbon microspheres were studied. Research indicates that after hydrothermal treatment, under the multi-level structural action of a small amount of proteins in corn stalks, the naturally occurring cellulose, polysaccharide organic compounds, and part of the ash in the stalks are adsorbed and encapsulated within the long-chain network structure formed by proteins and cellulose. By attaching silicate nanoparticles with certain rigidity from the ash to the relatively stable chair-type structure in cellulose, functional dense-structured carbon microspheres were ultimately prepared. These carbon microspheres could still effectively reduce fluid loss at 200 °C. The permeability recovery value of the cores treated with modified biomass carbon microspheres during flowback reached as high as 88%, which was much higher than that of the biomass itself. With the dense network-like chain structure supplemented by small-molecule aldehydes and silicate ash, the subsequent invasion of drilling fluid was successfully prevented, and a good sealing effect was maintained even under high-temperature and high-pressure conditions. Moreover, since this functional dense-structured carbon microsphere achieved sealing through a physical mechanism, it did not cause damage to the formation, showing a promising application prospect. Full article

Herein, a novel super-hygroscopic material, steam-exploded modified corn stalk pith (SE-CSP), was developed from corn stalk pith (CSP) via the steam explosion (SE) method, and its hygroscopic properties and mechanisms were evaluated. The results confirmed that SE effectively removed lignin and hemicellulose, disrupted the thin cell walls of natural CSP, and formed an aligned porous structure with capillary channels. SE changed the bonding distribution and surface morphology, and enhanced the crystallinity and thermal stability of CSP. The equilibrium hygroscopic percentage of SE-CSP (62.50%) was higher than that of CSP (44.01%) at 25 °C and 80% relative humidity (RH), indicating significantly greater hygroscopicity. The hygroscopic process of SE-CSP followed a Type III isotherm and fitted the Guggenheim–Anderson–de Boer (GAB), Peleg, and pseudo-first-order kinetic models. This process exhibited multi-layer adsorption with enthalpy-driven, exothermic behavior, primarily through physical adsorption involving hydrogen bonds and van der Waals forces. This work offered a new approach for advancing sorption dehumidification technology. Full article

Toxicity and pollution of heavy metals in water environments are very serious threats, and how to efficiently remove heavy metals is a difficult problem in water ecosystems. This study takes Cr and Pb as examples to study the adsorption effects of different types of modified biochar on these two heavy metals and their influencing mechanisms, with the aim of providing precise treatment schemes for water ecological health. Biochar was prepared from apricot branches, apricot shells, and corn stalks through nitrogen doping modification, and its structure and properties were characterized and analyzed. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to investigate the microstructure and surface chemical characteristics of the biochar. Adsorption experiments were conducted to evaluate its removal efficiency for Cr⁶⁺ and Pb²⁺ from aqueous solutions. The results showed that nitrogen-doped biochar prepared from corn stalks at 600 °C exhibited the highest Cr⁶⁺ adsorption rate of 81.09%, while the biochar prepared at 500 °C demonstrated the highest Pb²⁺ adsorption rate of 91.61%. Comparative analysis of FTIR and SEM data between nitrogen-doped biochar and its original counterparts revealed the underlying adsorption mechanisms, which involve a synergistic effect of coordination interaction, electrostatic attraction, and chemical reduction. This study highlights nitrogen-doped biochar as an efficient and cost-effective material for the removal of heavy metal ions from aqueous environments. It also provides theoretical and practical insights into the resource utilization of agricultural waste and the management of water pollution. Full article

Herein, biochars derived from corn stalks, rice husks, and bamboo powder were modified by nitric acid oxidation and sodium hydroxide alkali activation to identify efficient and cost-effective polycyclic aromatic hydrocarbon-adsorbent and microbial-immobilized carriers. The surface characterization and adsorption investigation results suggested that acid/alkali modification promoted the phenanthrene removal ability in an aqueous solution of biochars via facilitating π–π/n–π electron donor–acceptor interactions, electrostatic interactions, hydrogen bonds, and hydrophobic interactions. Subsequently, the degrading bacteria Rhodococcus sp. DG1 was successfully immobilized on the rice husk-derived biochar with nitric acid oxidation (RBO), which exhibited the maximum phenanthrene adsorption efficiency (3818.99 µg·g⁻¹), abundant surface functional groups, and a larger specific surface area (182.6 m²·g⁻¹) and pore volume (0.141 m³·g⁻¹). Degradation studies revealed that the microorganisms immobilized on RBO by the adsorption method yielded a significant phenanthrene removal rate of 80.15% after 30 days, which was 38.78% higher than that of the control. Conversely, the polymer gel network-based microenvironment in the microorganism-immobilized RBO by the combined adsorption–embedding method restricted the migration and diffusion of nutrients and pollutants in the reaction system. This study thus introduces an innovative modified biochar-based microbial immobilization technology characterized by a simple design, convenient operation, and high adsorption efficiency, offering valuable insights into material selection for PAH contamination bioremediation. Full article

In order to achieve the purpose of efficiently removing lead and cadmium as the main heavy metals from wastewater, this paper explores the adsorption properties of cadmium ions and lead ions on biochar under different modified conditions prepared from corn stalks as raw materials and potassium phosphate as surface modifiers. Before preparing biochar (BC), the mass ratios of 1:1 and 1:2 (corn stalks to potassium phosphate) were used for pre-modification, and the oxygen-restricted pyrolysis processes of 350 °C, 550 °C and 750 °C were used for treatment. The study discussed the individual and composite adsorption effects of biochar on Pb²⁺ and Cd²⁺ under different conditions. The experimental results show that phosphorus modification has changed the physical and chemical properties of the original biochar. Among them, the biochar (2PBC550) with an impregnation ratio of 1:2 and a pyrolysis temperature of 550 °C (2PBC550) exhibits excellent adsorption properties. When the pH of the simulated wastewater is 5 and the amount of adsorbent is 30 mg·L⁻¹, the maximum adsorption capacity of Pb²⁺ and Cd²⁺ is 145.48 mg·g⁻¹ and 14.533 mg·g⁻¹, respectively, which are 6.46 times and 3.67 times of the original biochar. The Pb²⁺ and Cd²⁺ adsorption data of 2PBC550 fit well with the quasi-secondary dynamics and Langmuir isothermal models, indicating that the adsorption process is controlled by single-layer chemical adsorption. In the composite metal system of Pb²⁺ and Cd²⁺, 2PBC550 exhibits a stronger affinity for Pb²⁺ than Cd²⁺. Through the analysis of characterization methods such as SEM, FTIR, XRD and XPS, it is proved that the adsorption of Pb²⁺ and Cd²⁺ by 2PBC550 is due to precipitation, complexation and π electron interaction. Therefore, 2PBC550 shows great application potential in the repair of wastewater containing Pb²⁺ or Cd²⁺. Full article

Soil biochar is a kind of organic matter rich in carbon, which is of great significance in soil fertility improvement, fertilizer type innovation and greenhouse gas emission reduction. In this paper, Mg-modified biochar was prepared by thermal cracking using rice straw and corn straw as raw materials. The Mg-modified biochar and unmodified biochar were fully mixed with prepared soil samples at the addition amounts of 0.5% (w/w), 1% (w/w) and 2% (w/w), respectively, and then simulated indoor soil cultivation experiments were carried out. The effects of magnesium ion-modified biochar and non-modified biochar on soil chemical properties and the effects of different amounts of biochar on soil properties were studied. The results showed that the yield of Mg-modified biochar from rice straw and corn straw, prepared by pyrolysis, was 65%, and the ash content was large. The pH of MG-modified corn stalk biochar (MCBC) is weakly basic (8.55), while the pH of MG-modified rice stalk biochar (MRBC) is basic (10.1), and their internal structures are slightly different. After the application of biochar prepared from rice straw and maize stover, soil indicators were determined. Compared to the control, the chemical properties of the treated soil samples were significantly improved, with an increase in soil pH, an increase in the content of effective nutrients, such as fast-acting potassium, fast-acting phosphorus and alkaline dissolved nitrogen, and an increase in the content of the total phosphorus and total nitrogen, as well as an increase in the content of organic matter. The Mg-modified biochar was generally superior to the unmodified biochar in improving soil fertility, at the same addition level. It was also found that the rice-straw biochar performed better than the corn-stover biochar and had a more obvious effect on soil improvement in terms of fast-acting potassium, ammonium nitrogen, nitrate nitrogen, total phosphorus and total nitrogen contents. Full article

As an agricultural waste, a large amount of corn stalk will cause environmental pollution. In order to realize the resource utilization of waste and meet the strict requirements of modern traffic on pavement strength and durability, it was modified and applied to an AC-13 asphalt mixture to study its influence on the road performance of asphalt mixture and its mechanism. The road performances of modified corn stalk fiber, lignin fiber, and ordinary asphalt mixtures were evaluated via the wheel tracking test, low-temperature bending test, water immersion Marshall test, freeze–thaw splitting test, and fatigue test. Based on the results of three-point bending fatigue test, the viscoelastic parameters and indexes of the fiber asphalt mixture were obtained by fitting the loading specimen and deflection data with the Burgers constitutive model, and the creep strain response was analyzed by applying dynamic load, so as to explore the relationship between the viscoelastic characteristics and creep behavior of modified corn stalk fiber and AC-13 mixture. The long-term high-temperature performance test of the asphalt mixture with the best fiber content was carried out by using the long-term pavement intelligent monitoring equipment independently developed by the group of investigators. According to the findings, the ideal fiber contents for modified corn and lignin in asphalt mixture are 0.2% and 0.3%, respectively. Among them, the modified corn stalk fiber with a 0.2% content has the best effect on road performance, viscoelastic performance, and the asphalt mixture’s creep behavior under dynamic load. Compared with the 0.3% lignin fiber asphalt mixture, its dynamic stability, bending stiffness modulus, immersion residual stability, freeze–thaw splitting strength ratio, and loading times at failure increased by 19.9%, 18.28%, 4.19%, 8.6%, and 9.15%, respectively. Compared with ordinary asphalt mixture, it increased by 47.0%, 28.72%, 7.65%, 15%, and 75.81%, respectively. Moreover, when modified corn stalk fiber is added at 0.2%, the viscoelastic delay time of asphalt mixture is the longest, the strain peak value and rut depth are at a minimum, and the viscoelastic properties, creep properties, and long-term high-temperature properties are the best. Full article

The type and content of modified stalk fibers significantly influence the fatigue properties of asphalt binder. In this study, different concentrations of NaOH solution were used to modify stalk fibers, and scanning electron microscopy (SEM) was used to observe the effect of the modified concentration on the fiber morphology. A dynamic shear rheology (DSR) test and a linear amplitude sweep (LAS) test were conducted to analyze the effects of the fiber type and content on various factors such as the complex shear modulus G*, phase angle δ, and fatigue parameters (A₃₅ and B). Consequently, the fatigue life N_f of the fiber asphalt binder was calculated using a viscoelastic continuum damage model. The results show that stalk fibers modified using a 5% alkali solution exhibited the best oil absorption and heat resistance, the asphalt binder with a 1.5%–2% fiber content exhibited the best resistance to fatigue, and the fatigue performance of the asphalt binder with different types of fibers was superior when fiber doping was at 1.5%. Additionally, the fatigue parameter A₃₅ of the modified cotton and corn stover fibers increased by 40.5% and 57.6%, respectively, and the fatigue parameter B decreased by 5.8% and 4.8%, respectively, compared with that of the unmodified stover fibers. Finally, the modified corn stalk fiber asphalt binder with a 1.5% fiber content demonstrated the best fatigue resistance. Full article

Water treatment alternatives such as adsorption using agricultural residues are currently being studied to eliminate pollutants that cause eutrophication in water bodies, avoiding the alteration of aquatic ecosystems. In this work, two bio-adsorbents were prepared using cellulose extracted from corn stems, Zea mays, which were labeled as MC (quaternized cellulose modified with Cetyl trimethyl ammonium chloride) and B 1:1 (biochar obtained by the impregnation of the biomass with an H₂SO₄ solution, 50% v/v, using a ratio of 1:1% weight of biomass to volume, followed by carbonization at 520 °C for 30 min with a heating rate of 10 °C/min). FTIR, TGA, DSC, and SEM-EDS were used to study the properties of the bio-adsorbents. The effect of temperature over nitrate and phosphate adsorption in the selective and binary system at 100 mg/L was tested at five temperatures: 25, 30, 35, 40, and 45 °C, using a load of the pollutant of 100 mg/L, volume of 5 mL, and a rate of bio-adsorbent of 2 g/L at 200 rpm. Results showed a phosphate removal of 29.1% using the B 1:1 bio-adsorbent at 30 °C and 23.8% with the MC bio-adsorbent at 35 °C. In the case of nitrate, removal of 40% was determined with the B 1:1 bio-adsorbent at 25 °C, while removal of 38.5% was attained at 30 °C after using the MC bio-adsorbent. The equilibrium was reached at 420 min. Nitrate adsorption with the MC sample showed a good adjustment to the pseudo-second-order model. The pseudo-first-order model described the kinetics of phosphate removal with MC, while this model had a good fit with the B 1:1 sample for nitrate and phosphate. Freundlich’s model also adjusted the adsorption equilibrium for both anions with acceptable accuracy. Moreover, the binary study indicated selectivity for the phosphate, suggesting the potential applications of the carbon-based bio-adsorbents for anionic ions remotion in aqueous media. Full article

Barley straw (BS-C) and corn stalks (CS-C) modified by citric acid are hopeful adsorbents for the removal of cationic dyes from aqueous solutions. Optimization of adsorption factors to improve removal of methylene blue (MB) and malachite green (MG) on BC-C and CS-C was carried out by response surface methodology with central composite design. The effect of pH, time, dye concentration, and adsorbent dose on the removal efficiency of cationic dyes was investigated. The experimental data were in good agreement with the predicted data obtained by mathematical models. Accordingly, the maximum MB removal efficiency on BS-C of 97% was achieved with a pH of 6.4, time of 50 min, an adsorbent dose of 11 g L⁻¹, and an initial MB concentration of 26 mg L⁻¹; the maximum MG removal efficiency on BS-C of 95% was achieved with a pH of 7.2, time of 60 min, an adsorbent dose of 14 g L⁻¹, and an initial MG concentration of 24 mg L⁻¹; the maximum MB removal efficiency on CS-C of 97% was achieved with a pH of 6.5, time of 45 min, an adsorbent dose of 11 g L⁻¹, and an initial MB concentration of 20 mg L⁻¹; the maximum MG removal efficiency on CS-C of 94% was achieved with a pH of 6.6, time of 50 min, an adsorbent dose of 12 g L⁻¹, and an initial MG concentration of 24 mg L⁻¹. Full article

The potential application of biochar in water treatment is attracting interest due to its sustainability and low production cost. In the present study, H₃PO₄-modified porous biochar (H-PBC), ethylenediaminetetraacetic acid-modified porous biochar (E-PBC), and NaOH-modified porous biochar (O-PBC) were prepared for Ni(II) and Pb(II) adsorption in an aqueous solution. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Brunauer–Emmett–Teller analysis (BET), and Fourier-transform infrared (FT-IR) spectroscopy were employed to characterize the as-obtained samples, and their capacities for Ni(II) and Pb(II) adsorption were determined. SEM showed that H-PBC retained the hierarchical porous structure of pristine biochar. FT-IR showed that H-PBC possessed abundant oxygen-containing and phosphorus-containing functional groups on the surface. BET analysis demonstrated that the surface areas of H-PBC (344.17 m²/g) was higher than O-PBC (3.66 m²/g), and E-PBC (1.64 m²/g), respectively. H-PBC, E-PBC, and O-PBC all exhibited excellent performance at Ni(II) and Pb(II) adsorption with maximum adsorption capacity of 64.94 mg/g, 47.17 mg/g, and 60.24 mg/g, and 243.90 mg/g, 156.25 mg/g, and 192.31 mg/g, respectively, which were significantly higher than the adsorption capacity (19.80 mg/g and 38.31 mg/g) of porous biochar (PBC). Pseudo-second order models suggested that the adsorption process was controlled by chemical adsorption. After three regeneration cycles, the Ni(II) and Pb(II) removal efficiency with H-PBC were still 49.8% and 56.3%. The results obtained in this study suggest that H-PBC is a promising adsorbent for the removal of heavy metals from aqueous solutions. Full article

The modification of agricultural wastes and their use as low-cost and efficient adsorbents is a prospective pathway that helps diminish waste and decrease environmental problems. In the present research, the natural adsorption capacity of corn stalks (CS) was improved by modification of their surface with citric acid. The adsorption capacity of the modified corn stalks (CS-C) was determined with the help of cationic dyes (methylene blue and malachite green). The equilibrium, kinetics, and thermodynamics of the cationic dyes on CS-C were studied. The Langmuir isotherm model best fitted the data both for methylene blue and malachite green adsorption on CS-C. The adsorption kinetics of the cationic dyes was well described by the pseudo-second order model. Thermodynamic studies revealed that adsorption of the cationic dyes on CS-C was an endothermic process. Negative results of ΔG^o (between −31.8 and −26.3 kJ mol⁻¹) indicated that the adsorption process was spontaneous in all the tested temperatures. The present study verified that citric acid-modified corn stalks can be used as a low-cost and effective adsorbent for removal of cationic dyes from aqueous solutions. Full article

The maximum gasification rate of corn stalk char (CSC) appeared at high conversion range, and its quite different gasification behaviors from other carbonaceous materials are all derived from the catalytic effect of alkali and alkali earth metals (AAEMs), so it is necessary to study the effect of AAEMs and gasification kinetics of such biomass char. However, there are few systematic discussions about this effect and kinetic modeling. Thus, in this study, CSC samples were prepared in a fast pyrolysis fixed-bed reactor, and its gasification experiments were conducted on a pressurized magnetic suspension balance at various total pressures (0.1–0.7 MPa), steam concentrations (10–70 vol.%) and temperatures (725–900 °C). Moreover, a water-leached CSC (H₂O-CSC) was also prepared to evaluate the impact of AAEMs on the gasification performance of CSC, and some well-known models were adopted to describe the gasification behaviors. On the basis of these results, the effect of primary AAEMs on the gasification behaviors of CSC and gasification kinetic modeling were obtained. Results showed total pressure had no obvious influence on the gasification rate of CSC, and the reaction order varied at 0.43–0.55 with respect to steam partial pressures. In addition, the modified random pore model (MRPM) and Langmuir–Hinshelwood (L-H) model were satisfactorily applied to predict the gasification behaviors of CSC. The catalytic effect of AAEMs on CSC gasification was weakened due to water-leaching treatment. A random pore model (RPM) could describe the gasification behavior of H₂O-CSC well, followed by grain model (GM) and volumetric model (VM). Full article