Organic matter (OM) derived from the decomposition of crop residues plays a key role as a sorbent for cadmium (Cd) immobilization. Few studies have explored the straw decomposition processes with the presence of minerals, and the effect of newly generated organo-mineral complexes on heavy metal adsorption. In this study, we investigated the variations in structure and composition during the rice straw decomposition with or without minerals (goethite and kaolinite), as well as the adsorption behavior and mechanisms by which straw decomposition affects Cd immobilization. The degree of humification of extracted straw organic matter was assessed using excitation-emission matrix (EEM) fluorescence and Ultraviolet-visible spectroscopy (UV-vis), while employing FTIR spectroscopy and XPS to characterize the adsorption mechanisms. The spectra analysis revealed the enrichment of highly aromatic and hydrophobic components, indicating that the degree of straw decomposition and humification were further intensified during incubation. Additionally, the existence of goethite (SG) accelerated the humification of OM. Sorption experiments revealed that the straw humification increased Cd adsorption capacity. Notably, SG exhibited significantly higher adsorption performance compared to the organic matter without minerals (RS) and the existence of kaolinite (SK). Further analysis using FT-IR spectroscopy and XPS verified that the primary mechanisms involved in Cd immobilization were complexion with -OH and -COOH, as well as the formation of Cd-π binds with aromatic C=C on the surface of solid OMs. These findings will facilitate understanding the interactions of the rice straw decomposing with soil minerals and its remediation effect on Cd-contaminated farmland.

Biopolymers are polymers of natural origin and are environmentally friendly, carbon neutral and less energy-intense additives that can be used for various geotechnical applications. Biopolymers like xanthan gum, carrageenan, chitosan, agar, gellan gum and gelatin have shown potential for improving subgrade strength, erosion resistance, and as canal liners and in slope stabilization. But minimal research has been carried out on cellulose-based biopolymers, particularly microcrystalline cellulose (MCC), for their application in geotechnical and geo-environmental engineering. In this study, the effect of MCC on select geotechnical properties of kaolin, a weak, highly compressible clay soil, like its liquid and plastic limits, compaction behavior, deformation behavior, unconfined compression strength (UCS) and aging, was investigated. MCC was used in dosages of 0.5, 1.0, 1.5 and 2% of the dry weight of the soil, and the dry mixing method was adopted for sample preparation. The results show that the liquid limit increased marginally by 11% but the plasticity index was nearly 74% higher than that of untreated kaolin. MCC rendered the treated soil stiffer, which is reflected in the deformation modulus, which increased with both dosage and age of the treated sample. The UCS of kaolin increased with dosage and curing period. The maximum UCS was observed for a dosage of 2% MCC at a 90-day curing period. The increase in stiffness and strength of the treated kaolin with aging points out that MCC can be a potential soil stabilizer.

Clay-algae flocculation is a promising method to remove harmful algal blooms (HABs) in aquatic ecosystems. Many HAB-generating species, such as Microcystis aeruginosa (M. aeruginosa), a common species in lakes, produce toxins and harm the environment, human health, and the economy. Natural clays, such as bentonite and kaolinite, and modification of these clays have been applied to mitigate HABs by forming large aggregates and settling down. In this study, we aim to examine the impact of laponite, a commercially available smectite clay that is synthetic, transparent, compatible with human tissues, and degradable, on removing HABs. We compare the cell removal efficiencies (RE) of laponite, two natural clays, and their polyaluminum chloride (PAC)-modified versions through clay-algae flocculation experiments. Our results show that the optimum concentrations of laponite, bentonite, kaolinite, PAC-modified bentonite, and PAC-modified kaolinite to remove 80 % of the M. aeruginosa cells from the water column are 0.05 g/L, 2 g/L, 4 g/L, 2 g/L and 0.3 g/L respectively. Therefore, to achieve the same cell removal efficiency, the amount of laponite needed is 40 to 80 times less than bentonite and kaolinite, and 6 times less than PAC-modified kaolinite. We demonstrate that the superior performance of laponite clay is because of its smaller particle size, which increases the encounter rate between cells and clay particles. Furthermore, experiments using water samples from Powderhorn Lake confirmed laponite\'s effectiveness in mitigating HABs. Our price analysis also suggests that this commercially-available clay, laponite, can be used in the field at a relatively low cost.

The extraction of phosphorite ore in Tunisia has resulted in the discharge of substantial amounts of phosphatic sludge into the region\'s water system. To mitigate this environmental issue and prevent heavy metal leaching, a geopolymerization process was employed using two types of Tunisian calcined phosphate sludges (Cal-PS1 and Cal-PS2) as substitutes for alkali-activated metakaolin. This study aimed to investigate and compare the physical and mechanical properties of the resulting geopolymers. The optimal substitution ratio of metakaolin with calcined phosphate sludge was determined to be 1.5, equivalent to 20 wt.% of calcined phosphate sludge. Compressive strength tests conducted after 28 days of curing revealed values of 37 MPa for Cal-PS1 specimens and 28 MPa for Cal-PS2 geopolymers while compressive strength of geopolymers soaked in water for 28 days showed a decrease with the addition of phosphate sludges. The specific surface areas of Cal-PS1 geopolymers ranged from 16.3 to 16.9 m2/g and from 17.62 to 18.73 m2/g for Cal-PS2 specimens exhibiting a mesoporous structure. The elasticity modulus of the geopolymers was found to increase with the increase of the apparent density of geopolymers and with the sludges content but it tended to be lower than the Portland cement elasticity modulus. Leaching test was conducted to evaluate the potential environmental applications of the geopolymers. This test demonstrated effective containment of heavy metals within the geopolymers\' network, except for low levels of arsenic.

This study surveyed the fates of artificial sweeteners in influent, effluent, and sewage sludge (SS) in wastewater treatment plant, and investigated the effects of Micro-Kaolin (Micro-KL) and Nano-Kaolin (Nano-KL) on nitrogen transformation and sucralose (SUC) and acesulfame (ACE) degradation during SS composting. Results showed the cumulative rate of ACE and SUC in SS was ∼76 %. During SS composting, kaolin reduced NH3 emissions by 30.2-45.38 %, and N2O emissions by 38.4-38.9 %, while the Micro-KL and Nano-KL reduced nitrogen losses by 14.8 % and 12.5 %, respectively. Meanwhile, Micro-KL and Nano-KL increased ACE degradation by 76.8 % and 84.2 %, and SUC degradation by 75.3 % and 77.7 %, and significantly shifted microbial community structure. Furthermore, kaolin caused a positive association between Actinobacteria and sweetener degradation. Taken together, kaolin effectively inhibited nitrogen loss and promoted the degradation of ACE and SUC during the SS composting, which is of great significance for the removal of emerging organic pollutants in SS.

Clay minerals are ubiquitous in subsurface environments and have long been recognized as having a limited or negligible impact on the fate of arsenic (As) due to their negatively charged surfaces. Here, we demonstrate the significant role of kaolinite (Kln), a pervasive clay mineral, in enhancing As(V) immobilization during ferrous iron (Fe(II)) oxidation at near-neutral pH. Our results showed that Fe(II) oxidation alone was not capable of immobilizing As(V) at relatively low Fe/As molar ratios (≤2) due to the generation of Fe(III)-As(V) nanocolloids that could still migrate easily as truly dissolved As did. In the presence of kaolinite, dissolved As(V) was significantly immobilized on the kaolinite surfaces via forming Kln-Fe(III)-As(V) ternary precipitates, which had large sizes (at micrometer levels) to reduce the As mobility. The kaolinite-induced heterogeneous pathways for As(V) immobilization involved Fe(II) adsorption, heterogeneous oxidation of adsorbed Fe(II), and finally heterogeneous nucleation/precipitation of Fe(III)-As(V) phases on the edge surfaces of kaolinite. The surface precipitates were mixtures of amorphous basic Fe(III)-arsenate and As-rich hydrous ferric oxide. Our findings provide new insights into the role of clay minerals in As transformation, which is significant for the fate of As in natural and engineered systems.

Grapevine varieties from \"Douro Superior\" (NE Portugal) experience high temperatures, solar radiation, and water deficit during the summer. This summer\'s stressful growing conditions induce nucleic acids, lipids, and protein oxidation, which cause cellular, physiological, molecular, and biochemical changes. Cell cycle anomalies, mitosis delay, or cell death may occur at the cellular level, leading to reduced plant productivity. However, the foliar application of kaolin (KL) can mitigate the impact of abiotic stress by decreasing leaf temperature and enhancing antioxidant defence. Hence, this study hypothesised that KL-treated grapevine plants growing in NE Portugal would reveal, under summer stressful growing conditions, higher progression and stability of the leaf mitotic cell cycle than the untreated (control) plants. KL was applied after veraison for two years. Leaves, sampled 3 and 5 weeks later, were cytogenetically, molecularly, and biochemically analysed. Globally, integrating these multidisciplinary data confirmed the decreased leaf temperature and enhanced antioxidant defence of the KL-treated plants, accompanied by an improved regularity and completion of the leaf cell cycle relative to the control plants. Nevertheless, the KL efficacy was significantly influenced by the sampling date and/or variety. In sum, the achieved results confirmed the hypothesis initially proposed.

Effective bleeding management strategies in uncontrollable and noncompressible massive hemorrhage are becoming important in both clinical and combat situations. Here, a novel approach was developed to create a superporous and highly absorbable hemostatic sponge through a facile chemical gas-foaming method by cross-linking long-chain polyphosphate along with nanokaolin and Ca2+ in an alginate structure to synergistically activate the coagulation pathway. Natural kaolin obtained from the Marand mine in East Azarbaijan was converted into pseudohexagonal-shaped kaolin nanoparticles (30 to 150 nm) using ball milling followed by a newly developed glow discharge plasma treatment method. The obtained ultralight sponges (>90% porosity) exhibit ultrarapid water/blood absorption capacity (∼4000%) and excellent shape memory, which effectively concentrates coagulation factors. The results of in vitro tests demonstrated that the proposed sponges exhibited enhanced blood clotting ability (BCI < 10%) and superior cohesion with red blood cells (∼100) and platelets (∼80%) compared to commercially available hemostatic products. The in vivo host response results exhibited biosafety with no systemic and significant local inflammatory response by hematological, pathological, and biochemical parameter assessments. In a rat femoral artery complete excision model, the application of alginate/k/polyp nanocomposite sponges resulted in a complete hemostasis time of 60 s by significant reduction of hemostasis time (∼6.7-8.3 fold) and blood loss (∼2-2.8-fold) compared to commercially available hemostatic agents (P < 0.001). In conclusion, distinct physical characteristics accompanied by unique chemical composition multifunctional sponges activate hemostasis synergistically by triggering the XII, XI, X, IX, V, and II factors and the contact pathway and have the ability of rapid hemostasis in noncompressible severe bleeding.

This investigation\'s novelty and objective reside in exploring catalytic flash pyrolysis of cross-linked polyethylene (XLPE) plastic residue in the presence of kaolin, with the perspective of achieving sustainable production of gasoline-range hydrocarbons. Through proximate analysis, thermogravimetric analysis, and heating value determination, this study also assessed the energy-related characteristics of cross-linked polyethylene plastic residue, revealing its potential as an energy source (44.58 MJ kg-1) and suitable raw material for pyrolysis due to its low ash content and high volatile matter content. To understand the performance as a low-cost catalyst in the flash pyrolysis of cross-linked polyethylene plastic residue, natural kaolin was subjected to characterization through thermogravimetric analysis, X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). Cross-linked polyethylene plastic residue was subjected to thermal and catalytic pyrolysis in an analytical microreactor coupled to gas chromatography-mass spectrometry (Py-GC/MS system), operating at 500 °C, to characterize the distribution and composition of volatile reaction products. The application of kaolin as a catalyst resulted in a decline of the relative concentration of hydrocarbons in the diesel range (C8-C24) from approximately 87 % to 28 %, and a reduction in lubricating oils (C14-C50) from about 70 % to 13 %, while concomitantly increasing the relative concentration of lighter hydrocarbons in the gasoline range (C8-C12) from around 28 % to 87 %. Therefore, catalytic flash pyrolysis offers the potential for converting this plastic waste into a new and abundant chemical source of gasoline-range hydrocarbons. This process can be deemed viable and sustainable for managing and valorizing cross-linked polyethylene plastic residue.

Ultra-small Ag nanoparticles (<5 nm) loaded on a kaolinite surface were successfully prepared in large batches by a dry-process, displaying excellent broad-spectrum antimicrobial ability and size-dependent activity. This Ag-loaded kaolinite (Ag@AT/K) inhibited the growth of pathogenic bacteria and accelerated wound healing in in vivo experiments on MRSA-infected wounds. This work provides a new strategy for the preparation of mineral-based nanoscale antibacterial materials.