Arsenic (As), a highly toxic and carcinogenic heavy metal, poses significant risks to soil and water quality, while oxytetracycline (OTC), a widely used antibiotic, contributes to environmental pollution due to excessive human usage. Addressing the coexistence of multiple pollutants in the environment, this study investigates the simultaneous adsorption of As(III) and OTC using a novel bimetallic zinc-iron-modified biochar (1Zn-1Fe-1SBC). The developed adsorbent demonstrates enhanced recovery, improved adsorption efficiency, and cost-effective operation. Characterization results revealed a high carbon-to-hydrogen ratio (C/H) and a specific surface area of 1137 m² g⁻¹ for 1Zn-1Fe-1SBC. Isotherm modeling indicated maximum adsorption capacities of 34.7 mg g⁻¹ for As(III) and 172.4 mg g⁻¹ for OTC. Thermodynamic analysis confirmed that the adsorption processes for both pollutants were spontaneous (ΔG < 0), endothermic (ΔH > 0), and driven by chemical adsorption (ΔH > 80 kJ mol⁻¹), with increased system disorder (ΔS > 0). The adsorption mechanisms involved multiple interactions, including pore filling, hydrogen bonding, electrostatic attraction, complexation, and π-π interactions. These findings underscore the potential of 1Zn-1Fe-1SBC as a promising adsorbent for the remediation of wastewater containing coexisting pollutants.

Usages of hospital sludge as a biochar adsorbent for wastewater treatment plants were investigated. Microwave carbonization was used to carbonize the sludge and then chemically activated with ZnCl₂ to increase surface area and porosity. A newly designed amine functional group’s doped Sludge Biochar Carbon (SBC) presents effective inorganic arsenic (As (III)) and organic arsenic (Dimethylarsinic Acid, DMA) adsorption in water. The pore volume, pore size distribution and specific surface area were determined by performing nitrogen adsorption-desorption measurements. The Fourier Transform Infrared of the SBC was recorded to study the functional groups at room temperature. The composition of SBC was further determined by X-ray Photoelectron Spectroscopy. In order to understand the effect of amine functional complexes on arsenic adsorption, the adsorption mechanism of As (III) and DMA on SBC surfaces modified with amine functional complexes was studied using Density Functional Theory (DFT). DFT results showed that both physical and chemical adsorption of As (III) and DMA on SBC surfaces occurred. The participation of amine functional complexes greatly promoted the surface activity of SBC surface and its adsorption capacity on arsenic. The physical adsorption energies of As (III) and DMA on SBC surface with amine functional complexes were − 38.8 and − 32.4 kJ mol^− 1, respectively. The chemical adsorption energies of As (III) and DMA on SBC surface with amine functional complexes were − 92.9 and − 98.5 kJ mol^− 1, respectively.

Gac fruit (Momordica cochinchinensis Spreng.) is a prominent source of carotenoids, renowned for its exceptional concentration of these compounds. This study focuses on optimizing the extraction of active components from the aril of gac fruit by evaluating the effects of extraction temperature, solid–liquid ratio, and extraction time. The primary objective is to maximize the yield of gac oil while assessing its antioxidant capacity. To analyze the kinetics of the solid–liquid extraction process, both first-order and second-order kinetic models were employed, with the second-order model providing the best fit for the experimental data. In addition, the potential of gac fruit peel as a precursor for biochar production was investigated through carbonization. The resultant biochars were evaluated for their efficacy in adsorbing crystal violet (CV) dye from aqueous solutions. The adsorption efficiency of the biochars was found to be dependent on the carbonization temperature, with the highest efficiency observed for BCMC550 (91.72%), followed by BCM450 (81.35%), BCMC350 (78.35%), and BCMC250 (54.43%). The adsorption isotherm data conformed well to the Langmuir isotherm model, indicating monolayer adsorption behavior. Moreover, the adsorption kinetics were best described by the pseudo-second-order model. These findings underscore the potential of gac fruit and its byproducts for diverse industrial and environmental applications, highlighting the dual benefits of optimizing gac oil extraction and utilizing the peel for effective dye removal.

Arsenic is a kind of metal elements, widely distributed in nature. Many technologies, including adsorption, ion exchange, membrane separation and extraction, have been developed to treat arsenic-containing wastewater due to a series of drinking water safety problems caused by arsenic pollution. Biochar has some advantages of big surface area, low cost and so on. Therefore, waste wood was used as biochar, FeCl3·6H2O and KMnO4 were also used to promote the performance of arsenic removal. The results of XRD, BET, EA and VSM analysis show that modified biochar has major elements of Fe, Mn with KMnO4. The modified biochar (Fe1Mn1C1) has higher magnetism of 40 emu g-1. Through adsorption performance assessment, the best ratio of Fe/C is 1:1 and the adsorption efficiency and capacity of Fe1C1 is 61.6% and 0.681 mg g-1, respectively. Then, the best ratio of Mn, Fe and C is 4:1:1 with highest adsorption efficiency of 80.8% and capacity of 0.724 mg g-1. The best dosage of Fe1C1 and Fe1Mn2C1 is the same as 1 g L-1. It shows better adsorption capacity under higher pH with pristine biochar (PB) and Fe1C1 while under lower pH with Fe1Mn2C1. The adsorption patterns of PB and Fe1Mn2C1 fit Langmuir well. In contrast, adsorption pattern of Fe1C1 fits Freundlich well. In addition, three types of biochars all fit the pseudo second order adsorption kinetics.

Usages of hospital sludge as a biochar adsorbent for wastewater treatment plants were investigated. Microwave carbonization was used to carbonize the sludge and then chemically activated with ZnCl 2 to increase surface area and porosity. A newly designed amine functional group’s (DETA) doped sludge biochar carbon (SBC) presents effective inorganic arsenic (As(III), As 2 O 3 ) and organic arsenic (p-ASA, C 2 H 7 AsO 2 ) adsorption in water. The pore volume, pore size distribution and specific surface area were determined by performing nitrogen adsorption-desorption measurements (BET). The Fourier transform infrared (FTIR) of the SBC was recorded to study the functional groups at room temperature. The composition of SBC was further determined by X-ray photoelectron spectroscopy (XPS). In order to understand the effect of amine functional complexes on arsenic adsorption, the adsorption mechanism of As 2 O 3 and p-ASA on SBC surfaces modified with amine functional complexes was studied using density functional theory (DFT). Results showed that both physical and chemical adsorption of As 2 O 3 and p-ASA on SBC surfaces occurred. The participation of amine functional complexes greatly promoted the surface activity of SBC surface and its adsorption capacity on arsenic. The physical adsorption energies of As 2 O 3 and p-ASA on SBC surface with amine functional complexes were -38.4 and -32.8 KJ mol -1 , respectively. Other hand, the chemical adsorption energies of As 2 O 3 and p-ASA on SBC surface with amine functional complexes were -92.9 KJ mol -1 and -98.5 KJ mol -1 , respectively.

Arsenic contamination in groundwater poses serious health risks, as exemplified by the Blackfoot disease epidemic in Taiwan, which was caused by prolonged arsenic exposure. This study investigates the use of biochar derived from the wastewater treatment sludge of the Far Eastern Memorial Hospital (New Taipei City, Taiwan) as an efficient adsorbent for arsenic removal. A novel iron-doped sludge biochar (Fe-SBC) was developed to enhance arsenic adsorption efficiency, facilitate adsorbent recovery, and reduce operational costs. The adsorption mechanism of arsenic on Fe-SBC, modified with iron hydroxide complexes, was examined through Density Functional Theory (DFT) simulations. The results demonstrate a high arsenic removal efficiency of approximately 90% using continuous adsorption systems. The DFT calculations revealed strong chemical interactions between arsenic and the biochar, evidenced by high adsorption energy (−156.8 kJ mol⁻¹) and a short bond distance (1.48 Å), correlating with the high adsorption performance observed experimentally. Additionally, arsenic byproducts desorbed from the adsorbent were repurposed into antibacterial agents and pigments. Four distinct pigment colors—green, blue, gray, and orange—were produced through different preparation methods, with the antibacterial agents showing effective antimicrobial properties. This study highlights the potential of Fe-SBC for sustainable arsenic remediation and resource recovery.