In this study, a ternary MgO-impregnated eggshell–kaolin (EKM) composite was synthesized and evaluated for fluoride removal from water under fixed-bed column adsorption. The composite, prepared by co-precipitation and wet impregnation, was characterized using XRD, FTIR, SEM–EDX, and Brunauer–Emmet–Teller analyses. Results confirmed successful integration of the three components, yielding a mesoporous structure with a surface area of 158.5 m 2 g −1 . The composite exhibited good defluoridation performance under varying operational conditions. Higher bed depth and lower flow rate enhanced adsorption capacity, achieving up to 6.35 mg g −1 at 10 mg L −1 influent fluoride concentration. Breakthrough data were well described by the Thomas, Clark, and Yoon–Nelson models ( R 2 ≥ 0.94 ) at lower influent concentration, moderate flow rate, and greater bed depth, while the bed depth service time model confirmed a linear increase in service time with bed depth. The adsorbent maintained good regeneration ability across four cycles. Co-existing anions showed interference with the uptake of F − , with inhibitory effects following the order: PO 4 3 − > SO 4 2 − > NO 3 − > Cl − . The study estimated that 11.11 g of EKM composite yields 2 L of safe water for less than USD1. These results highlight the EKM composite as an efficient and sustainable adsorbent for practical defluoridation applications.

Octafluoropropane (C 3 F 8 ) is widely used as etching agent in refrigeration, air conditioning and semiconductor industries. However, due to its long lifespan and strong infrared absorbing ability, once C 3 F 8 is emitted, the atmospheric radiation absorbing ability will be permanently altered, which will result in a serious greenhouse effect. Therefore, the efficient removal technology of C 3 F 8 is crucial in protecting the environment and alleviating the greenhouse effect. In this work, a series of X-ETS-4 (X: Mg, Ca, Sr, Ba) molecular sieves were synthesized by solvothermal and ion-exchange method. The morphology and structure of the prepared X-ETS-4 were characterized by FT-IR, XRD, and SEM, etc. The adsorption performance of the X-ETS-4 on C 3 F 8 are determined by fixed-bed adsorption breakthrough experiments and single-component isothermal adsorption experiments. The adsorption mechanism was investigated using different adsorption theoretical models. The results show that Ba-ETS-4 exhibits high adsorption capacity and high adsorption selectivity for C 3 F 8 , achieving C 3 F 8 adsorption separation at very low concentration (C 3 F 8 /N 2 volume ratio = 1:400). The saturated adsorption capacity of Ba-ETS-4 on C 3 F 8 reaches 155.17 mg/g (298 K, 170 kPa), which is 15.49 times more than that of Na-ETS-4. In addition, the ideal adsorption solution theory (IAST) separation selectivity of C 3 F 8 /N 2 reaches 341–941 in the pressure range of 0–170 kPa.

The reduction and resource recovery of waste incineration fly ash represent a central focus of current research initiatives. In this study, Ca-Al-layered double hydroxides (LDHs) were prepared via a coprecipitation method using waste incineration fly ash as a calcium source combined with aluminum chloride. Their Pb 2+ adsorption capacities were compared with commercial LDHs and LDHs synthesized from chemical reagents. Results indicate that the optimal Ca/Al molar ratio for both fly ash-derived LDHs and reagent-synthesized LDHs was 2:1. The Pb 2+ adsorption capacities of fly ash-derived LDHs (FCA2), reagent-synthesized LDHs (CA2), and commercial LDHs (CL) were 1149.78 mg·g −1 , 1024.00 mg·g −1 , and 1069.34 mg·g −1 , respectively. After five regeneration cycles, FCA2 maintained stable adsorption performance, with Pb 2+ removal efficiency exceeding 95%. The synthesized LDHs were characterized by SEM, XRD, FTIR and BET, revealing that the dominant adsorption mechanisms included ion exchange, surface complexation, and precipitation. This study not only proposes a method for high-value resource utilization of waste incineration fly ash but also provides insights for aquatic heavy metal pollution control and hazardous waste management.

Chromium (VI) contamination in water presents significant environmental and public health challenges, demanding efficient and sustainable remediation strategies. This study explores the use of biochar (BC) derived from the invasive plant Mimosa pigra, modified with hydroxyapatite (HAp), to form a composite (BC@HAp) for effective Cr VI removal. HAp is known for its high adsorption capacity and biocompatibility, and its incorporation into BC enhances heavy metal removal through synergistic effects. BC and BC@HAp were synthesized via the sol–gel method and tested under various conditions including pH, adsorbent dosage, Cr VI concentration, contact time, and temperature. Structural and morphological analyses confirmed improved surface characteristics of BC@HAp. The composite exhibited a significantly higher Cr VI adsorption capacity (67.68 mg/g) compared to unmodified BC (39.95 mg/g), attributed to increased surface area and new functional moieties. The adsorption mechanism was facilitated by electrostatic attraction between Cr VI anions (HCrO 4 − , Cr 2 O 7 2− ) and positively charged Ca 2+ sites, ion exchange with surface carbonate and phosphate groups, and surface complexation involving hydroxyl (–OH) and carboxyl (–COOH) groups. Adsorption followed the Freundlich and Temkin isotherms, indicating heterogeneous surface interactions, and was best described by the Elovich kinetic model. Thermodynamic parameters revealed the process to be spontaneous and endothermic, favoring higher temperatures. The enhanced performance of BC@HAp demonstrates its potential as a cost-effective and eco-friendly solution for both Cr VI remediation and invasive species utilization.

Low-cost activated carbon electrodes derived from Moringa oleifera seeds were developed for the efficient removal of Arsenic from contaminated water by capacitive deionization (CDI). The electrodes were synthesized using a carbon slurry composed of Moringa oleifera powder (MOP), poly(vinylidene fluoride), and carbon black. Scanning electron microscopy was used to analyze the surface morphology. In contrast, their electrochemical properties, including capacitance and electrical conductivity, were analyzed through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The capacitance values, as determined from CV and EIS measurements, were 201.3 Fg −1 and 122.62 Fg −1 for MOP (MOP-1:1 and MOP-1:2), respectively. The Arsenic removal efficiency was evaluated under optimized electrochemical conditions, achieving an efficiency of 89.38% when treating a 100 mg/L arsenite solution at an applied voltage of 1.2 V and pH 9. These findings highlight the potential of Moringa oleifera seeds-derived carbon electrodes as sustainable, cost-effective materials for Arsenic removal through CDI.

This study examines the influence of surfactants with varying hydrocarbon chain lengths—tetradecyltrimethylammonium bromide (TDAB), octadecyltrimethylammonium bromide (ODAB), and docosyltrimethylammonium bromide (DKAB)—on the structure and properties of montmorillonite (a bentonite clay) with a cation exchange capacity of 101 mmol/100 g. Structural modifications were analyzed using X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravimetric analysis (TGA), and microscopy techniques. Intercalation of these surfactants increased the interlayer spacing of montmorillonite from 1.24 nm (raw) to 1.98 nm, 2.17 nm, and 2.32 nm for TDAB-, ODAB-, and DKAB-modified samples, respectively. IR spectral analysis confirmed the incorporation of the hydrocarbon chains and a resulting decrease in clay hydrophilicity. TGA demonstrated enhanced thermal stability in the modified clays, with the highest residual mass (17.43%) observed for DKAB-modified bentonite. The decrease in the point of zero charge (pH p zc) of the clay from 9.6 (raw bentonite) to approximately 9.0 in the modified samples reflects a change in the electrochemical state of the surface. Water vapor adsorption decreased from 0.183 g/g (raw clay) to 0.086 g/g in modified samples, while benzene vapor adsorption increased. Adsorption studies with organic dyes showed a maximum sorption capacity of 10.6 mg/g for methylene blue on ODAB-modified clay and 13.6 mg/g for Congo red on TDAB-modified clay, reflecting enhanced affinity due to interlayer expansion and improved surface properties. These findings highlight the potential of surfactant-modified bentonites for improved adsorption applications.

The increasing CO 2 emission leads to significant ecological changes, and the control of CO 2 emissions has been a major concern worldwide. Solid adsorbents are a highly promising carbon capture technology; the regeneration energy, visually representing the operating cost, is a key parameter to judge the merit of different solid adsorbents. In this paper, a uniform energy consumption calculation method was proposed to compare the characteristics of CO 2 adsorbents in temperature swing adsorption process. The results showed that, for chemisorbents with strong interactions with CO 2 (e.g. alkali and alkaline earth metal-based adsorbents), due to the high adsorption heat and the high regeneration temperature required, their energy consumption in CO 2 capturing was quite high. It could be even higher than that of 30% monoethanolamine solution. Adsorption heat plays an important role in the cyclic regeneration of adsorbents; a very low adsorption heat (<25 kJ/mol) will make it difficult to form the difference in adsorption capacities between low and high temperatures. Among all the adsorbents, metal–organic frameworks, zeolites, and amine-functionalized adsorbents perform best, all of which possess moderate adsorption heats and large adsorption capacities at relatively low regeneration temperature.

This study aimed to investigate the behavior of nano olive pomace as a raw adsorbent and its biochar in adsorbing thorium (IV) ions (Th(IV)) from aqueous solutions. The study also evaluated and compared their adsorption capacity, removal, optimum adsorption conditions, as well as adsorption kinetics and isotherms. Both adsorbents were characterized by thermal gravimetric analysis, differential thermal analysis, Fourier transform infrared, scanning electron microscope, X-ray diffraction, Brunauer–Emmett–Teller (BET), elemental analysis, specific surface area, bulk density, pore volume, cation-exchange capacity, and pH pzc . The effects of initial concentration, initial pH, adsorbent dosage, contact time, and temperature on the adsorption onto olive pomace and biochar were investigated using the batch method. A pseudo-second-order kinetic model controlled the adsorption of Th(IV) ions, as shown by the kinetic analysis. The Langmuir isotherm best presented the isothermal data for olive pomace and biochar. The maximum Th(IV) adsorption capacities onto olive pomace and biochar were obtained as 68.0 and 154 mg/g at pH 4.0 and 45.0°C, respectively. The adsorption of Th(IV) onto olive pomace and biochar was an endothermic (positive ΔH°), spontaneous (negative ΔG°), and random process (positive ΔS°). After column adsorption, Th(IV) ions were recovered by treating the loaded biochar and olive pomace with 1.0 or 0.1 M HNO 3 . The first and second stages of recovery employing 1.0 M HNO 3 produced the highest recovery percent of Th(IV). The results showed that these adsorbents can be utilized effectively and affordably to extract Th(IV) ions.

Utilization of kiwi peel (KP) is proposed for gold recovery from electronic wastes (e-wastes). KP was simply modified by dehydration pretreatment with concentrated sulfuric acid. Among of the e-wastes metals, modified KP exhibited high selectivity on Au(III) adsorption. Ions dependencies on adsorption revealed that the increased chloride ion concentration has inhibition to Au(III) adsorption. After Au(III) adsorption, microscope images found gold particles on the adsorbents surface. X-ray diffraction analyses suggested that Au(III) reduction occurred along with the adsorption process, till the adsorption reached the equilibrium. Modified KP exhibited higher adsorption capacity (5.71 mmol g –1 ) than original KP (lower than 0.5 mmol g –1 ) or other natural adsorbents. Modification improved the adsorption capacity of KP. Gold was successfully recovered from the mixed precious metals through the adsorption and elution. KP waste is an applicable adsorbent with rich resource and high adsorption capacity.