Porous MgO-modified biochar adsorbents fabricated by the activation of Mg(NO3)2 for phosphate removal: Synergistic enhancement of porosity and active sites

Facile exfoliation of natural talc into separated mesoporous magnesium silicate nano-sheets for effective sequestration of phosphate and nitrate ions: characterization and advanced modeling

Magnesium silicate nano-sheets were synthesized from natural talc by facile exfoliation and delamination methods as exfoliated product (EXTC) of 29.5 nm average pore diamter, enhanced surface area (103 m2/g), and adsorption perforamnces. The sucessful development of EXTC particles was followed based on different techniques and applied in effective sequestration of PO4 3- and NO3 - ions from water. The EXTC product as adsorbent demonstrates remarkable effectiveness for both PO4 3- (257.9 mg/g) and NO3 - (164.2 mg/g) as compared to several studied structures. Depending on the steric analysis of Monolayer equilibrium model, the interface of EXTC highly saturated with interactive receptors for the both ions but with higher abundant for PO4 3- (151.5 mg/g) as compared to NO3 - (61.5 mg/g). This resulted in higher aggregation effect during the uptake of NO3 - (4 ions per site) than PO4 3- (3 ions per site) which also donate the vertical orientation of these adsorbed ions and operation of multi-ionic sequestration mechanisms. The structure is highly recyclable and of significant safety and cane be applied in its spent or exhausted state as fertilizer. The energetic evaluation considering the Gaussian energy (<8.5 kJ/mol) as well as the sequestration energy (<4 kJ/mol), suggested the predominant impact of physical mechanisms (hydrogen bonds and electrostatic attraction), in addition to the impact of the weak chemical complexation. Furthermore, the thermodynamic functions declare the retention of these ions into the framework of EXTC by exothermic and spontaneous reactions.

Green synthesized MgO combined with dielectric barrier discharge plasma enhanced phosphorus (P) recovery from livestock wastewater: A dual approach for management of wastewater and P resources

Phosphorus (P) recovery from wastewater using integrated techniques i.e., adsorption combined with advanced oxidation technologies is a novel approach for cleaning wastewater and preventing eutrophication. This approach, however, has not been extensively studied, particularly in the context of real wastewater applications. In this study, a green biomass-based sol-gel method was developed using potato starch (PS) and MgCl2·6H2O to synthesize MgO (PS-MgO). The unique synthesis method resulted in PS-MgO composed predominantly of spherical particles with an average size of about 103 nm and exhibited superior P adsorption performance compared to commercial MgO materials (GH-MgO and AD-MgO). The Langmuir maximum P adsorption capacity (mg/g) of the PS-MgO was 429.4, while that of the commercial GH-MgO and AD-MgO was 341.3 and 421.7, respectively, at the solution pH 7.0. The kinetic model fitting demonstrated that the adsorption rate of PS-MgO was faster than the two commercial MgOs. Importantly, PS-MgO can maintain a high P adsorption capacity across a wide pH range (425 mg/g at pH 5.0 and 369 mg/g at pH 11.0), whereas the P adsorption capacities of GH-MgO (153 at pH 5.0 and 297 at pH 11.0) and AD-MgO (422 at pH 5.0 and 200 at pH 11.0) were more pH-dependent. In addition, PS-MgO exhibits high selectivity for P capture in solutions containing coexisting ions, and the P-loaded PS-MgO can efficiently release P through acid or base treatment, highlighting its potential for reuse as a fertilizer. To enhance P recovery from real livestock wastewater, the dielectric barrier discharge (DBD) plasma technology was combined with MgO adsorption. The P recovery capacity of MgOs from livestock wastewater increased 1.4-1.7 times after DBD plasma treatment, attributed to the degradation of aromatic proteins and microbial metabolites. These findings provide new insights into the design of efficient and environmentally friendly materials for P recovery, while also demonstrating the potential of integrating advanced oxidation technologies with adsorption processes.

Electrospinning Synthesis of Nano-Scale MgO Fibers and Their Methylene Blue Adsorption Efficiency

Water pollution from industrial dyes like methylene blue poses severe environmental and health risks, necessitating effective wastewater treatment methods. Among various adsorbents, MgO stands out due to its high surface area, tunable porosity, and superior adsorption capabilities. This research presents the preparation of nano-scale magnesium oxide (MgO) fibers using electrospinning, followed by calcination at temperatures of 300 °C, 400 °C, 500 °C, 600 °C, and 700 °C. The effects of calcination temperatures on MgO's surface characteristics, microstructure, crystalline phases, and adsorption performance were investigated. SEM and TEM analyses revealed that fibers calcined at 500 °C possessed the most distinct porous structure, with a coarse surface and substantial pores, which enhanced adsorption properties. XRD analysis confirmed that the 500 °C calcined MgO fibers had the highest crystallinity, particularly the (200) crystal plane. Notably, BET surface area analysis confirmed the superior adsorption properties of these fibers, making them highly effective for wastewater treatment applications. Adsorption tests for methylene blue (MB) indicated that these fibers achieved a maximum dye removal efficiency of 52.52% and an adsorption capacity of 43.11 mg/g within 90 min. The adsorption process aligned with a quasi-second-order kinetic model (R2 = 0.9846) and fit the Langmuir isotherm (R2 = 0.991), indicating monolayer chemisorption. This study underscores the effectiveness of MgO fibers calcined at 500 °C, demonstrating enhanced adsorption characteristics that are beneficial for wastewater treatment applications.

Emerging contaminants in polluted waters: Harnessing Biochar's potential for effective treatment

Biochar is a carbon-rich, sponge-like material with intricate functionalities, making it suitable for various environmental remediation applications, including water treatment, soil amendment and, additives in construction materials, anaerobic digesters, and electrodes, among others. Its easy adaptability and low cost make it particularly attractive. This review highlights a range of biochar and surface-modified biochar exhibiting high uptake and degradation efficiencies for a broad spectrum of contaminants, including humic acid, disinfection by-products (DBPs), radioactive materials, dyes, heavy metals, antibiotics, microplastics, pathogens, Per- and polyfluoroalkyl substances (PFAS), and cytotoxins. The study provides a detailed discussion on different classes of pollutants and their removal mechanisms using biochar, covering processes like physical and chemical adsorption, electrostatic interactions, π-π interactions, hydrogen bonding, as well as surface complexation, chelation, among others. This review article stands out for its comprehensive exploration of biochar's effectiveness in removing a wide range of emerging contaminants, as well as recent advancements in the removal of conventional pollutants like heavy metals and antibiotics.

Competitive adsorption of polycyclic aromatic hydrocarbons on phosphorus tailing-modified sludge biochar provides mechanistic insights

Biochar has been widely used to solve the wastewater pollution of polycyclic aromatic hydrocarbons (PAHs). However, the competition of PAHs with different benzene ring numbers (e.g., phenanthrene [Phe], pyrene [Pyr], and benzo[a]pyrene [BaP]) for adsorption sites on biochar has received little attention. In this study, biochar was produced by co-pyrolysis of sludge and phosphorus tailing at different temperatures (300, 500, or 800 °C) to adsorb PAHs. The results show that phosphorus tailing increased the adsorption of PAH by increasing the biochar's BET surface area (SBET), micropore volume, hydrophobicity (at low temperatures) and aromaticity (at high temperatures). The maximum adsorption capacities were 29.90 µmol/g for Phe, 25.58 µmol/g for Pyr and 20.45 µmol/g for BaP, respectively. Importantly, the types and functions of groups involved in the adsorption of various PAHs were discussed. Adsorption of Phe and Pyr on the biochar mainly involved C=O and C-O-C functional groups, and there was a certain degree of competition between these PAHs for those sites. In contrast, BaP mainly adsorbed at C-OH and C=C moieties, without competing with Phe or Pyr at C-OH sites. The competitive edge of BaP was also stronger than that of Phe and Pyr on C=C functional groups. The adsorption mechanisms involving pore filling, hydrophobic interactions, and π-π interactions governed the adsorption of the evaluated PAHs. Overall, the adsorption of PAHs on biochar followed a heterogeneous chemical adsorption process.

Effective fabrication and characterization of eco-friendly nano particles composite for adsorption Cd (II) and Cu (II) ions from aqueous solutions using modelling studies

The public health and environment are currently facing significant risks due to the discharge of industrial wastewater, which contains harmful heavy metals and other contaminants. Therefore, there is a pressing need for sustainable and innovative technologies to treat wastewater. The main objective of this research was to develop novel composites known as chitosan, Padina pavonica, Fe(III), and nano MgO incorporated onto pomegranate peel with the specific purpose of removing Cd (II) and Cu (II) ions from aqueous solutions. The characterization of these nanocomposites involved the utilization of several analytical methods, including Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, thermal gravimetric analysis, and X-ray photoelectron spectroscopy. The efficiency of these nanocomposites was evaluated through batch mode experiments, investigating the impact of factors such as pH, initial concentration, contact time, and adsorbent dose on the adsorption of Cu(II) ions. The optimum conditions for the removal of ions were pH = 5 for Cu (II) and 6 for Cd (II), contact time: 120 min, adsorbent dosage: 0.2 g, initial metal ion concentration: 50 mg/L for each metal ion for the present study. The MgO@Pp demonstrated the highest removal efficiencies for Cu(II) and Cd(II) at 98.2% and 96.4%, respectively. In contrast, the CS@Fe-PA achieved removal efficiencies of 97.2% for Cu(II) and 89.2% for Cd(II). The modified MgO@Pp exhibited significantly higher total adsorption capacities for Cu(II) and Cd(II) at 333.3 and 200 mg/g, respectively, compared to CS@Fe-PA, which had capacities of 250 and 142 mg/g, respectively. The adsorption of Cd (II) and Cu (II) ions by MgO@Pp was found to be a spontaneous process. The R2 values obtained using the Freundlich and Redlich-Peterson models were the highest for the MgO@Pp composite, with values of 0.99, 0.988, 0.987, and 0.994, respectively, for Cu (II) and Cd (II). The pseudo-second-order equation was determined to be the best-fit kinetic model for this process. Reusability experiments confirmed that the adsorbents can be utilized for up to four regeneration cycles. Based on the findings of this study, MgO @ Pp is the most promising alternative and could be instrumental in developing strategies to address existing environmental pollution through adsorption.

Enhanced removal of phosphate from aqueous solutions by oxygen vacancy-rich MgO microspheres: Performance and mechanism

The efficient removal of phosphate from water environments was extremely significant to control eutrophication of water bodies and prevent further deterioration of water quality. In this study, oxygen vacancy-rich magnesium oxide (OV-MgO) microspheres were synthesized by a simple solvothermal method coupling high-temperature calcination. The effects of adsorbent dosage, contact time, initial pH and coexisting components on phosphate adsorption performance were examined. The physicochemical properties of OV-MgO microspheres and the phosphate removal mechanisms were analyzed by various characterization techniques. The maximum adsorption capacity predicted by the Sips isotherm model was 379.7 mg P/g for OV-MgO microspheres. The phosphate adsorption in this study had a fast adsorption kinetics and a high selectivity. OV-MgO microspheres had a good acid resistance for phosphate adsorption, but their adsorption capacity decreased under alkaline conditions. The electrostatic attraction, ligand exchange, surface precipitation, inner-sphere surface complexation and oxygen vacancy capture were mainly responsible for efficient removal of phosphate from aqueous solutions. This study probably promoted the development of oxygen vacancy-rich metal (hydr)oxides with potential application prospects.

Phosphogypsum-Modified Vinasse Shell Biochar as a Novel Low-Cost Material for High-Efficiency Fluoride Removal

In this study, vinasse shell biochar (VS) was easily modified with phosphogypsum to produce a low-cost and novel adsorbent (MVS) with excellent fluoride adsorption performance. The physicochemical features of the fabricated materials were studied in detail using SEM, EDS, BET, XRD, FTIR, and XPS techniques. The adsorption experiments demonstrated that the adsorption capacity of fluoride by MVS was greatly enhanced compared with VS, and the adsorption capacity increased with the pyrolysis temperature, dosage, and contact time. In comparison to chloride and nitrate ions, sulfate ions significantly affected adsorption capacity. The fluoride adsorption capacity increased first and then decreased with increasing pH in the range of 3-12. The fluoride adsorption could be perfectly fitted to the pseudo-second-order model. Adsorption isotherms matched Freundlich and Sips isotherm models well, giving 290.9 mg/g as the maximum adsorption capacity. Additionally, a thermodynamic analysis was indicative of spontaneous and endothermic processes. Based on characterization and experiment results, the plausible mechanism of fluoride adsorption onto MVS was proposed, mainly including electrostatic interactions, ion exchange, precipitation, and hydrogen bonds. This study showed that MVS could be used for the highly efficient removal of fluoride and was compatible with practical applications.

Study on the removal effect and mechanism of calcined pyrite powder on Cr(VI)

Pyrite exhibits considerable potential as an adsorbent in wastewater treatment. However, few pyrite adsorbents are directly obtained from natural pyrite, as most are composite materials that require a complex preparation process. To develop a pyrite-based adsorbent with a simple preparation process, pyrite was processed by calcination at 400, 600, and 800 °C for 4 h and ball-milled into a fine powder. The adsorption properties of the pyrite powder were systematically explored. The calcined pyrite powder was characterized by SEM-EDS and XRD. The results revealed that the pyrite calcined at 600 °C exhibited excellent adsorption properties and was primarily composed of Fe7S8. The optimum conditions for Cr(VI) removal were a temperature of 45 °C, an adsorbent dosage of 1 g, an equilibration time of 60 min, and an initial pH of 3. Moreover, the calcined pyrite powder exhibited excellent reusability, and the Cr(VI) removal rate exceeded 65% after three cycles. The Cr(VI) adsorption on pyrite can be well described by the Freundlich model and pseudo-second-order kinetic equation. The calcination temperature is the main factor affecting the adsorption performance of pyrite. Therefore, the calcined pyrite powder is expected to be an excellent adsorbent for Cr(VI) in the wastewater treatment industry.

Magnesium oxide nanoparticles modified biochar derived from tea wastes for enhanced adsorption of o-chlorophenol from industrial wastewater

In this work, magnesium oxide nanoparticles supported biochar derived from tea wastes (MgO@TBC) was prepared as an effective adsorbent for removing hazardous o-chlorophenol (o-CP) from industrial wastewater. The surface area, porous structure, surface functional groups and surface charge of tea waste biochar (TBC) significantly enhanced after the modification process. The best uptake performance of o-CP was found at pH = 6.5 and 0.1 g of MgO@TBC adsorbent. According to the adsorption isotherm, the adsorption of o-CP onto MgO@TBC followed the Langmuir model with a maximum uptake capacity of 128.7 mg/g, which was 26.5% higher than TBC (94.6 mg/g). MgO@TBC could be reused for eight cycles with a high o-CP uptake performance (over 60%). Besides, it also exhibited good removal performance of o-CP from industrial wastewater with a removal rate of 81.7%. The adsorption behaviors of o-CP onto MgO@TBC are discussed based on the experimental results. This work may provide information to prepare an effective adsorbent for removing hazardous organic contaminants in wastewater.