Enhanced adsorption of phenol from aqueous solution by KOH combined Fe-Zn bimetallic oxide co-pyrolysis biochar: Fabrication, performance, and mechanism

Multifunctional cellulose-rich bagasse magnetic biochar capable of efficient elimination and separation of purine compounds in beer: DFT calculation and practical system applications

Purine compounds in beer significantly increase the risk of hyperuricemia and gout, creating a strong demand for low-purine and healthy beer. A multifunctional cellulose-rich bagasse (cellulose content: 40 %-50 %) magnetic porous carbon (MABB) was constructed by employing alkali-modified bagasse and intercalating with Fe3+ to effectively remove three purine nucleosides (NUCs) in beer, namely, guanosine (GUA), adenosine (ADE), and inosine (INO). Characterization results showed that alkalization increased the specific surface area of MABB and iron oxide acted as an active site to facilitate NUC removal. The equilibrium adsorption capacities of MABB for GUA, ADE, and INO were 307.12, 317.16, and 303.37 mg/g, respectively. Analysis of adsorption mechanisms and density functional theory calculations revealed that pore adsorption, metal complexation, electrostatic attraction, and hydrogen bonding interactions are dominant in MABB adsorption of NUCs. In practical system of homemade beer, MABB demonstrated significant purine removal efficacy. The treatment achieved 82.66 % purine reduction (from initial 110.04 to residual 19.08 mg/L), thereby confirming its operational viability. While minor alterations in physicochemical parameters were observed post adsorption, all critical quality indicators remained compliant with brewing standards. This study proposes an effective adsorption-based strategy for purine removal, offering mechanistic insights and a theoretical framework for industrial low-purine beer production.

Mechanisms of Phenol Adsorption on Banana Leaves and Coffee Husk Biochars

In this study, biochars were produced from banana leaves (BB) and coffee husk (BC) for phenol adsorption. The biochars were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, textural analysis, point of zero charge measurement, and determination of surface acidic and basic groups. For both biochars, a higher pyrolysis temperature led to losses of oxygenated groups as well as increases of graphitic structures and greater basic character. For biochars produced at 400 °C, phenol adsorption kinetics was best described by the pseudo-second-order model. Chemisorption involving π-π interactions was identified as the main adsorption mechanism. For biochars produced at 500 °C, a smaller pore size resulted in limited adsorption by intraparticle diffusion. The Freundlich model provided the best fit to the isotherm data due to the high surface heterogeneity. Moreover, the results also suggested the formation of multilayers or pore filling as adsorption mechanisms for the obtained biochars. The maximum adsorption capacity values (q e) were 13.8 and 21.2 mg g-1 for phenol adsorption on BB400 and BB500, and 17.3 and 19.1 mg g-1 for BC400 and BC500, respectively. The results showed that the agroindustrial residues are suitable for phenol adsorption in aqueous solutions.

Biochar doping of synthesized mordenite improves adsorption and oxidation in As(III) removal: Experiments and DFT calculations

In this study, a composite material was synthesized through the co-pyrolysis of biochar doped with synthetic mordenite. The adsorption experiments conducted with BC@ASM on As(III) facilitated the determination of the optimal mass ratio of 20:1 (ASM: Yak dung) and a pyrolysis temperature of 500 °C. The adsorption properties of ASM and BC@ASM were examined through batch adsorption experiments and a range of characterization techniques. And the reaction mechanism was further elucidated by DFT calculations, revealing the essential difference in the adsorption of As(III) by ASM and BC@ASM. The adsorption kinetics of As(III) were found to align with both the pseudo-second-order and Elovich kinetic models, while the isothermal adsorption was consistent with the Freundlich model. The maximum theoretical adsorption capacities were determined to be 371.9 mg/g and 449.6 mg/g, respectively. When the initial concentration of arsenite (As(III)) is 100 mg/L, the optimal dosage of synthetic mordenite is determined to be between 6 and 8 g/L, while the optimal dosage of the composite material ranges from 5 to 6 g/L. The composite material demonstrated significant resistance to fluctuations in pH. Within the pH range of 2-12, the removal efficiency is sustained between 78.3% and 88.7%. Furthermore, the adsorption capacity exhibited minimal sensitivity to the presence of anions such as chloride (Cl⁻), nitrate (NO₃⁻), bicarbonate (HCO₃⁻), and sulfate (SO₄2⁻) in the surrounding environment. In addition, BC@ASM facilitated the formation of arsenite-tannic acid complexes, which markedly improved its adsorption capacity for arsenite. In conclusion, the composite material presents a viable approach for addressing arsenic contamination in aquatic environments, while the foundational data offers a novel perspective for the remediation of metallic pollutants.

Ultrahigh and rapid removal of Ni2+ using a novel polymer-zeolite-biochar tri-composite through one-pot synthesis route

In this work, a novel adsorbent from alginate, zeolite and biochar has been made through one-pot synthesis route with highly compatible Sodium Dodecyl Sulphate (SDS) modification. This gave ultra-high Ni2+ removal of 1205 mg/g in batch mode while treating almost 200 L of solution in column mode with 1171 mg/g capacity, which are the one of the highest reported values. The Point of Zero Charge (pHzpc) for Ni2+ removal was determined to be 5, with optimal removal efficiency being observed at pH 7, indicating a negative surface charge of the ABPC beads, which aligns with the anionic charge provided by SDS enhancement. Mechanistic studies have been done to show the most prominent mechanisms of metal removal besides demonstrating stability up to 20 cylces with desorption efficiency as high as 97%. The adsorbent is found to be highly cost effective at 1.87USD per kg.

Enhanced adsorption of phenolic compounds using biomass-derived high surface area activated carbon: Isotherms, kinetics and thermodynamics

The progress of industrial and agricultural pursuits, along with the release of inadequately treated effluents especially phenolic pollutant, has amplified the pollution load on environment. These organic compounds pose considerable challenges in both drinking water and wastewater systems, given their toxicity, demanding high oxygen and limited biodegradability. Thus, developing an eco-friendly, low-cost and highly efficient adsorbent to treat the organic pollutants has become an important task. The present investigation highlights development of a novel adsorbent (CFPAC) by activation of Cassia fistula pod shell for the purpose of removing phenol and 2,4-dichlorophnenol (2,4-DCP). The significant operational factors (dosage, pH, concentration, temperature, speed) were also investigated. The factors such as pH = 2 and T = 20°C were found to be significant at 1.6 g/L and 0.6 g/L dosage for phenol and 2,4-DCP respectively. Batch experiments were further conducted to study isotherms, kinetic and thermodynamics studies for the removal of phenol and 2,4-DCP. The activated carbon was characterised as mesoporous (specific surface area 1146 m2/g, pore volume = 0.8628 cc/g), amorphous and pHPZC = 6.4. At optimum conditions, the maximum sorption capacity for phenol and 2,4-DCP were 183.79 mg/g and 374.4 mg/g respectively. The adsorption isotherm was better conformed to Redlich Peterson isotherm (phenol) and Langmuir isotherm (2,4-DCP). The kinetic study obeyed pseudo-second-order type behaviour for both the pollutants with R2 > 0.999. The thermodynamic studies and the value of isosteric heat of adsorption for both the pollutants suggested that the adsorption reaction was dominated by physical adsorption (ΔHx < 80 kJ/mol). Further, the whole process was feasible, exothermic and spontaneous in nature. The overall studies suggested that the activated carbon synthesised from Cassia fistula pods can be a promising adsorbent for phenolic compounds.

Biochar/Delonix regia seed gum/chitosan composite as efficient adsorbent for the elimination of phenol from aqueous medium

In this study, biochar (BC) from Delonix regia pods peel and gum from Delonix regia seed (SG) were prepared, and also biochar/chitosan composite (BCS) and biochar/Delonix regia seed gum/chitosan composite (BCGS) were fabricated for the efficient adsorption of phenol. Various characterization tools such as SEM, TEM, ATR-FTIR, TGA, zeta potential, and textural investigation were studied to examine the features of the synthetized adsorbents, confirming their positive construction. It was fully studied how necessary factors, comprising pH, dose of adsorbent, contact shaking time, initial phenol concentration, and temperature influenced adsorption behavior. An obvious rise of the adsorption capacity from 60.16 to 165.20 mg/g was achieved by the modification of biochar with Delonix regia seed gum and chitosan under ideal circumstances of 2 h contact duration, pH 7, 15 °C, and a dose of 2.0 g/L. The phenol adsorption was well applied by Langmuir, Temkin, Dubinin-Radushkevich, and Sips isotherms, in addition to nonlinear pseudo-second-order kinetic model. Furthermore, the physisorption, endothermic, and spontaneous process was illustrated by thermodynamic investigation. Additionally, the fabricated adsorbents could be effectively used and regenerated without main losses of only 7.5, 4.6, and 4.0 % for BC, BCS, and BCGS, respectively in the removal percentage after seven cycles of application.

Enhanced adsorption of dye wastewater by low-temperature combined NaOH/urea pretreated hydrochar: Fabrication, performance, and mechanism

The highly stable biomass structure formed by cellulose, hemicellulose, and lignin results in incomplete conversion and carbonization under hydrothermal conditions. In this study, pretreated corn straw hydrochar (PCS-HC) was prepared using a low-temperature alkali/urea combination pretreatment method. The Mass loss rate of cellulose, hemicellulose, and lignin from pretreated biomass, as well as the effects of the pretreatment method on the physicochemical properties of PCS-HC and the adsorption performance of PCS-HC for alkaline dyes (rhodamine B and methylene blue), were investigated. The results showed that the low-temperature NaOH/urea pretreatment effectively disrupted the stable structure formed by cellulose, hemicellulose, and lignin. NaOH played a dominant role in solubilizing cellulose and the combination of low temperature and urea enhanced the ability of NaOH to remove cellulose, hemicellulose, and lignin. Compared to the untreated hydrochar, PCS-HC exhibited a rougher surface, a more abundant pore structure, and a larger specific surface area. The unpretreated hydrochar exhibited an adsorption capacity of 64.8% for rhodamine B and 66.32% for methylene blue. However, the removal of rhodamine B and methylene blue by PCS-BC increased to 89.12% and 90.71%, respectively, under the optimal pretreatment conditions. The PCS-HC exhibited a favorable adsorption capacity within the pH range of 6-9. However, the presence of co-existing anions such as Cl-, SO42-, CO32-, and NO3- hindered the adsorption capacity of PCS-HC. Among these anions, CO32- exhibited the highest level of inhibition. Chemisorption, including complexation, electrostatic attraction, and hydrogen bonding, were the primary mechanism for dye adsorption by PCS-HC. This study provides an efficient method for utilizing agricultural waste and treating dye wastewater.

Construction of aldehyde-based, ester-based hyper-cross-linked polar resin and its selective adsorption mechanism for phenol in coal chemical wastewater

Efficient and precise recovery of phenol from coal chemical wastewater (CCW) poses a significant challenge, prompting the development of a novel aldehyde-based, ester-based hyper-cross-linked polar resin (DES-COOC-CHO) in this study. Two distinct functional group modification methods were employed to enhance the screening effect of the resin. SEM, FT-IR, NMR, XPS, and BET characterizations confirmed the successful construction of the hyper-cross-linked polar resin, incorporation aldehyde and ester groups, exhibiting a special surface area of 627.2 m2/g and a microporous specific surface area percentage of 29.94%. DES-COOC-CHO adhered to the pseudo-second-order kinetic model and Langmuir model (maximum adsorption capacity of 118.0 mg/g). Its adsorption of phenol was spontaneous chemisorption, monolayer adsorption. Notably, even after undergoing 20 adsorption-desorption cycles, the resin maintained a stable adsorption capacity, showcasing excellent recoverability. In the presence of phenols sharing similar properties, DES-COOC-CHO exhibited superior selectivity for phenol. In real CCW, it achieved a remarkable 90% selective removal rate of phenol. The primary selective mechanism relied on the hydrogen bonding effect facilitated by aldehyde and ester groups, coupled with microporous sieving of appropriate size. In comparison with other adsorbent materials, DES-COOC-CHO exhibited superior adsorption properties, coupled with a cost-effective preparation process, presenting significant potential for practical applications.