Phosphorus (P) recovery from sewage sludge (SS) have been regarded as an effective method of P recycling. The effects of incineration temperature, incineration time, and chlorine additives on the distribution of P speciation during sludge incineration were studied. Moreover, the reactions between model compounds AlPO₄ and additives (MgCl₂ and CaCl₂) were investigated by thermogravimetric differential thermal analysis and X-ray diffraction measurements. The results demonstrated that the increase in temperature and time stimulated the volatilization of non-apatite inorganic phosphorus (NAIP) instead of apatite phosphorus (AP). MgCl₂ and CaCl₂ can greatly promote the conversion of NAIP to AP. Additionally, AlPO₄ reacted with MgCl₂ are incinerated at 500–600 °C to form Mg₃(PO₄)₂, which is mainly due to the reaction of the intermediate product MgO and AlPO₄. Reactions between AlPO₄ and CaCl₂ occurred at 700–750 °C and produced Ca₂PO₄Cl, which can be directly used with high bioavailability. These findings suggested that chlorine additives in the SS incineration process can obtain phosphorus-containing minerals with higher bioavailability to realize the resource utilization of P in sludge.

Photosynthetic microalgal growth is a promising tool for mitigation of gaseous effluent from the cement production, which is highly implicated in global warming and climate change. We investigated the effects of actual cement industry flue gas on the physiology of Chlorella vulgaris under laboratory-controlled conditions. We evaluated the growth, photosynthetic performance, intracellular metal content, total proteins, and carbohydrates of C. vulgaris under three gas input rates: 9, 36, and 54 L d⁻¹; compressed air (54 L d⁻¹) was used as control. The results showed no correlation between the flue gas input rates on total proteins and carbohydrates in the algal biomass, and no effects on growth rates. However, rapid light curves indicated that the light use efficiency (α) and the maximum relative electron transport rate (rETRₘₐₓ) were stimulated when applying 9 and 36 L d⁻¹. Metal analysis revealed an accumulation of Cr, Zn, and Ni in the algal biomass exposed to flue gas (54 L d⁻¹) compared to the control. Thermogravimetry and differential thermal analysis showed that 70% of the cement kiln dust were composed by uncalcined limestone, which may have stimulated photosynthesis, as indicated by the rapid light curve parameters. In general, C. vulgaris can be considered a robust organism for cement flue gas bioremediation.

This study investigated methane (CH₄) adsorption by natural sepiolite—obtained from Eskisehir in Turkey—and its Ag-, Cu-, Fe-, and H-exchanged forms by using a volumetric gas adsorption method. Sepiolite was modified with 1 M AgNO₃, 1 M Cu(NO₃)₂∙3H₂O, 1 M Fe(NO₃)₃∙9H₂O, and 1 M HCl solutions at 80 °C for 6 h, respectively. The natural and modified sepiolite samples were characterized by using X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG-DTG), differential thermal analysis (DTA), and the nitrogen adsorption method. Quantitative XRD analysis showed that the sample consisted primarily of sepiolite clay mineral and dolomite as an impurity in small amounts. It was found that acid and heavy metal treatments caused apparent changes in the structure and microporosity of the sepiolite samples. CH₄ adsorption isotherms of clay samples were examined at temperatures of 0 °C and 25 °C and pressures up to 100 kPa. It was determined that the CH₄ adsorption capacities of sepiolite samples increased at both temperatures according to the following sequence: CuS < AgS < HS < S < FeS. CH₄ adsorption values of sepiolite samples varied between 0.084 mmol/g and 0.299 mmol/g. It was observed that the CH₄ adsorption capacities of heavy metal cation-exchange clay samples were related to the surface area.

ZnAl-layered double hydroxide-loaded banana straw biochar (ZnAl-LDH-BSB) was prepared via the hydrothermal method, and the efficient phosphorus removal agent ZnAl-LDO-BSB was obtained by calcination at 500 °C. Based on the ZnAl-LDO-BSB adsorption characteristics, the adsorption mechanism was evaluated via TG/DTA, FTIR, XRD, SEM, HRTEM, and other characterization methods. The results showed that the ZnAl-LDO-BSB assembled into microspheres with typical hexagonal lamellar structures and presented good thermal stability. The adsorption of total phosphate (TP) by ZnAl-LDO-BSB conforms to the Langmuir model, and the theoretical maximum adsorption capacity is 185.19 mg g⁻¹. The adsorption kinetics were in accordance with the second-order kinetic model, and the anion influence on TP adsorption followed the order CO₃²⁻ > SO₄²⁻ > NO₃⁻. The combination of zeta potential measurements with the FTIR, XRD, SEM, HRTEM, and XPS results suggested that ZnAl-LDO-BSB adsorbs TP mainly by electrostatic adsorption, surface coordination, and anion intercalation. Graphical abstract

In this study, we investigated the effects of SiO₂ nanoparticles (SiO₂-NPs) (1, 10, 25, 50, and 100 mg/L) for 24 h in vitro on the motility parameters and oxidative stress markers such as total glutathione (TGSH), catalase (CAT), and malondialdehyde (MDA) of rainbow trout, Oncorhynchus mykiss sperm cells. Therefore, SiO₂-NPs were synthesized with sol-gel reaction from tetraethoxy orthosilicate (TEOS). The prepared nanoparticle structures were characterized for chemical structure, morphology and thermal behavior employing Fourier transform infrared spectroscopy, X-ray spectroscopy, scanning electron micrograph, and thermal analysis (DTA/TGA/DSC) techniques. After exposure, there was statistically significant (p < 0.05) decreases in velocities of sperm cells. CAT activity significantly (p < 0.05) decreased by 9.6% in sperm cell treated with 100 mg/L. In addition, MDA level significantly increased by 70.4% and 77.5% in sperm cell treated with 50 and 100 mg/L SiO₂-NPs, respectively (p < 0.05). These results showed that SiO₂-NPs may have toxic effect on rainbow trout sperm cells in 50 mg/L and more.

Fluoride can cause some diseases to humans when ingested in large quantities and for a long time. Due to this, it is necessary to remove or reduce the amount of fluoride in effluents before release into the water bodies. This work aimed to evaluate the ability of hydrocalumites synthesized by two different methodologies and calcined hydrocalumite in reducing the content of fluoride in aqueous solutions. The materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), N₂ physisorption, thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The removal capacity of fluoride ions ranged from 14.9 to 189.6 mg F⁻ g⁻¹. The removal mechanisms by hydrocalumites were ion exchange and adsorption at low concentrations, while at high concentrations were adsorption and precipitation of calcium fluoride. In relation to the use of calcined hydrocalumite, the removal mechanisms were ion exchange and reconstruction of structure (memory effect) in low concentrations. By the adsorption tests, it was observed that the results fit better the Langmuir isotherm model.

New approaches are required for prevention and control of biofilm-producing bacteria and consequently mitigating the health problems of bovine clinical mastitis. This work designed to determine prevalence rates of biofilm-producing bacteria that causing bovine clinical mastitis and evaluate the anti-biofilm effectiveness of novel nanocomposite of zinc–aluminum layered double hydroxide intercalated with gallic acid (GA) as chelating agent (Zn-Al LDH/GA) on the prevention and control of environmental pathogenic bacteria; Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), Staphylococcus aureus (S. aureus), and Coagulase-negative staphylococci (CNS), besides Listeria monocytogenes (L. monocytogenes) and assess the ability to use as an antimicrobial agent, and/or sanitizer for milking equipment. All samples (n = 230) involved clinical mastitis cow’s milk (n = 50) beside environmental samples (n = 180) were collected then examined for isolation and identification of bacterial pathogens. Zn-Al LDH/GA nanocomposite was synthesized using co-precipitation method, then characterized by Fourier-transform infrared spectroscopy (FT-IR); X-ray diffraction (XRD); field emission scanning electron microscopy (FESEM); high-resolution transmission electron microscopy (HRTEM); thermogravimetric analysis (TGA); differential thermal analysis (DTA); zeta potential; DLS analysis; and Brunauer, Emmett, and Teller (BET) surface area. The anti-biofilm activity of nanocomposite against mastitis-causing bacteria was detected using the broth micro-dilution and disc-diffusion assay. Results, the minimum concentration of Zn-Al LDH/GA that inhibited the growth of gram-positive and negative bacteria, were 312–625 and 5000 μg/mL, respectively. The LD₅₀ of Zn-Al LDH/GA was determined in mice at 1983.3 mg/kg b.wt. As a conclusion, Zn-Al LDH/GA nanocomposite proved its efficiency as an antimicrobial agent and/or sanitizer used for cleaning of milking equipment, due to it could inhibit the growth and multiplication of potentially pathogenic bacteria that causing clinical mastitis and its formation of biofilm on the milking equipment. Zn-Al LDH/GA was found to use under varying pH conditions compared with other commercial sanitizer used besides the formation of nanocomposite increases the material stability.

As a commonly used surfactant, sodium dodecyl sulfate (SDS) usually coexists with inorganic anions in the industrial wastewater. These anions have a significant influence on SDS removal, indirectly threatening the environment. It is important to understand the relationship between the adsorption of SDS and inorganic anions. In this study, calcium-based layered double hydroxide (CaAl-LDH-Cl) as an efficient adsorbent was synthesized for investigating the effect of SO₄²⁻ on SDS removal. The SDS adsorption capacities were enhanced to 3.21 and 4.21 mmol g⁻¹ in the presence of SO₄²⁻ with low/high SDS concentration, respectively. The phenomenon and mechanism were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Scanning electron microscopy (SEM). Anionic exchange played a dominant role in the adsorption of SDS onto CaAl-LDH-Cl at DS⁻/SO₄²⁻ < 2, while both anion exchange and precipitation occurred when DS⁻/SO₄²⁻ exceeded 2. Moreover, the thermal analysis (TG–DTA) was employed to further reveal the interaction mechanism. The results showed the highest total mass loss and the lowest loss temperature of interlayer water in the sulfate coexist system, confirming the enhancement of SDS adsorption amount in the presence of SO₄²⁻.

In this study, Mn-doped MgAl-layered double hydroxides (LDHs) were successfully synthesized for efficient removal arsenate from aqueous solution. The structure and composition of Mn-doped MgAl-LDHs intercalated by different ions such as CO₃²⁻, Cl⁻, or NO₃⁻ were investigated. The characterizations of XRD, ATR FT-IR, SEM, TG-DTA, and N₂ adsorption-desorption presented that the Mn-doped MgAl-LDHs (donated as Mn-LDHs) have very similar physical morphologies and properties to the MgAl-Cl-LDHs (donated as Mg-LDHs). However, the Mn-LDHs exhibits more preferable arsenate adsorption than Mg-LDHs. The As(V) removal kinetics data of Mn-LDHs is followed pseudo-second-order expression. The adsorption capacity of As(V) on Mn-LDHs via Langmuir isotherm model was 166.94 mg g⁻¹. The results of XPS revealed that the enhanced removal mechanism can be attributed to surface complexation of As(V) with Mn on the surface of Mn-LDHs. These results prove that Mn-doped LDHs can be considered as a potential material for adsorption As(V) from wastewater.

Increases in global wildfires and fire severity are expected to result from global warming. Severe wildfires not only burn surface vegetation but also affect forest soil. Humic substances play key roles in the transport of nutrients and the carbon cycle in terrestrial ecosystems. In this study, we evaluated the effects of forest fires on the chemical properties of fulvic acid (FA) and humic acid (HA) extracted from non-burned and burned forest soils in Gunma, Japan. The differential thermal analysis of FA indicated that the intensity of exothermic reaction peak at 400 °C was 2-fold higher than that from non-burned soil. Based on pyrolysis-gas chromatography-mass spectrometry analysis with tetramethyl ammonium hydroxide, the amount of pyrolysate compounds in FA from burnt soil was significantly lower than that in FA from non-burnt soil. Therefore, we can conclude that the forest fire caused the significant change in the properties of FA such as increasing the aromaticity and refractory. In addition, the concentration of dissolved organic carbon with low molecular weight in surface soil increased after forest fire. This study suggests that the denaturation of soil organic matter by wildfire can affect the carbon cycle in terrestrial ecosystems.