The adsorption of the antiseptic drug chlorhexidine acetate by halloysite was studied. It was shown that the adsorption kinetic curves obeyed a pseudo-second-order reaction equation. The Langmuir and Freundlich models described well the equilibrium adsorption of chlorhexidine acetate by halloysite. The pristine halloysite powder and the loaded clay were characterized using physicochemical methods such as dynamic light scattering, scanning electron microscopy, X-ray diffraction, nitrogen adsorption–desorption, Fourier-transform infrared spectroscopy and thermal analysis. It was found that the halloysite particles were in the form of cylindrical tubes with sizes in the range of 50–1500 nm. Analysis of the X-ray diffraction data showed that the process of chlorhexidine acetate loading did not change the crystal structure of halloysite. The values of the textural parameters of the materials under study were determined using Brunauer–Emmett–Teller, Barrett–Joyner–Halenda and density functional theory methods. The findings indicated that, by filling the pores of halloysite with chlorhexidine acetate, the volume of the pore space and the pore surface area decreased. In addition, it was found from the biological activity tests that halloysite loaded with chlorhexidine acetate demonstrates antimicrobial activity against Escherichia coli M-17 bacteria.

Magnetite-enriched mining tailings are a cost-effective and abundant catalytic material with inherent magnetic recyclability. Yet their practical application in catalysis is often constrained by their limited surface area and sluggish reaction kinetics. To address these issues, we developed a facile one-step co-precipitation method to synthesize a magnetic nano-Fe3O4 (MNP) catalyst that exhibits enhanced surface reactivity for efficient activation of H2O2 towards tetracycline (TC) degradation. The system achieved complete (100%) removal of TC at an initial concentration of 20 mg L–1 within 90 min and demonstrated robust catalytic performance across weakly acidic to neutral pH conditions. Mechanistic investigations confirmed that ⋅OH is the primary reactive oxygen species involved, with ⋅O2⁻ and 1O2 providing supplementary contributions to the degradation. Remarkably, the intrinsic magnetic properties ensured efficient MNP catalyst recovery. This work provides a sustainable and scalable wastewater treatment strategy, leveraging mining tailings as a cost-effective resource to treat wastewater while also providing economic and environmental benefits.

To date, published studies have proven that the reactions at the iron/bentonite interface are complex and only partly understood. In the present study, mixtures of bentonite powder and iron powder were prepared, which allowed for varying individual parameters. The results confirmed some controversial previously reported conclusions and revealed new findings. More specifically, Na-exchanged samples showed a reduced extent of corrosion compared to Ca/Mg-exchanged ones, and the addition of reactive silica increased the extent of corrosion, which has not been reported to date. The negative temperature effect (less corrosion at higher temperatures), which was reported previously, could only be confirmed for Ca/Mg-bentonites. One Na-bentonite showed the opposite effect, but this sample also contained reactive silica in contrast to the others. The present study proves for the first time that the type of exchangeable cation can affect the type of corrosion product, which could be an explanation for why the 7 Å corrosion product was not reported in all corrosion tests (sometimes only magnetite was reported). In addition, experiments that ran for 36 months showed that the corrosion progress of six different bentonites was different. Three bentonite/iron mixtures did not show progress in corrosion after 12 months, whereas the other three showed ongoing corrosion. Using the former three bentonite/iron mixtures would significantly increase high-level radioactive waste canister lifetime, but future work should be devoted to the identification of the reason for this differing long-term performance, differing thermal behaviour and differing corrosion products resulting from different types of exchangeable cation.

Lead contamination in water poses serious risks to ecosystems and human health, highlighting the need for low-cost and efficient treatment technologies. In this study, natural attapulgite clay was thermally treated at various temperatures to improve its capacity for removing lead ions from aqueous solutions. The adsorbent prepared at 400°C exhibited the best performance, with a maximum adsorption capacity of 32.63 mg g–1. Characterization results indicated that while heating caused partial changes in the crystal structure, the nanorod morphology and key structural features of attapulgite were largely preserved. The enhanced adsorption ability was attributed to an increase in surface reactivity and greater accessibility of active functional groups. These findings demonstrate a simple and effective modification route that broadens the potential use of attapulgite for heavy-metal wastewater treatment.

Research on the special engineering properties of laterite has highlighted the importance of interactions between colloidal oxides and clay minerals, yet their exact microscopic mechanisms remain elusive. To address this, this study employs molecular dynamics simulations to investigate the impact of isomorphic substitution on the interactions between illite and colloidal alumina. The stable configurations and the potential of mean force for these interactions were determined. The simulation results reveal that the heterogeneous charge distribution across the surfaces of illite and colloidal alumina underpins their interaction. Specifically, the negatively charged {001} surface of illite forms a stable adsorption structure with the positively charged Al atoms of colloidal alumina. Meanwhile, equilibrium cations (K+) and atoms from isomorphic substitution induce electrostatic attractions with O and Al atoms in colloidal alumina, leading to two localized stable states and an intermediate transition state on the {00-1} surface of illite. Furthermore, Mg substitution in the octahedral sheet and Al substitution in the tetrahedral sheet reduce the layer charge density, thereby weakening the affinity of the illite {00-1} surface for colloidal alumina. Conversely, Fe substitution in the octahedral sheet increases the local charge density, enhancing the attraction of the {001} surface. These simulation results provide molecular-level insights into the mechanisms governing the behaviour of laterite, offering a theoretical foundation for guiding future experimental studies and for the engineering application and performance control of laterite soils.