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Diatomite-based porous ceramsite is a new kind of environmental material. In this study, ceramsite was prepared by wet grinding, a rolling-ball method, and high temperature-calcination using diatomite as the main raw material with the addition of a pore-forming agent and sintering assistant. X-ray diffraction, scanning electron microscopy, and mercury injection, were used to analyze the structure and characteristics of the prepared materials. Using hydroquinone as the target pollutant, the adsorption behavior of diatomite-based porous ceramsite was investigated. Results indicated that the diatomite-based porous ceramsite had a pore size ranging from 500 to 3000 nm, a specific surface area of 6.14 m2.g-1, and a porosity of 47.8%. When pH was 7, the removal rate and adsorption capacity of the hydroquinone by the diatomite-based porous ceramsite was 91.2% and 4.56 m2.g-1, respectively. In the adsorption process of hydroquinone by diatomite-based porous ceramsite, the diffusion of a liquid membrane was dominant, which could be better described by the quasi-first-order kinetic equation. The Langmuir and Koble-Corrigan equations had a higher fitting degree of data for the adsorption isotherms. The adsorption characteristics of the diatomite-based porous ceramsite are in accordance with the fixed-point adsorption of a single molecular layer and belong to a heterogeneous composite adsorption system. The correlation coefficient R2 and k value of hydroquinone adsorption by the diatomite-based porous ceramsite determined by the liquid film diffusion model were 0.848 and 0.0417, respectively.

This study investigates the removal of Congo red dye from aqueous solution using functionalized generation 3.0 and 5.0 Polyamidoamine dendrimer – silica gel composite (G-3PS, G-5PS). Fourier Transform-Infra Red spectroscopy, Brunauer Emmett and Teller, Thermogravimetric Analysis, pH at point of zero charge, and Scanning Electron Microscopy measurements have been applied to characterize the synthetic nanohybride composite, these techniques revealed the successful functionalization of both dendrimer molecules and subsequent immobilization onto silica gel. The implications of varying adsorption parameters such as contact time, initial concentration of adsorbate, temperature and pH on both composites were studied. Experimental data obtained from batch adsorption processes were fitted into two equilibrium isotherms (Langmuir and Freundlich) and 3 kinetic models (Pseudo-First-Order, Pseudo-Second-Order, Intra Particle Diffusion). Adsorption mechanism was mainly governed by film diffusion due to electrostatic interactions between the functionalized dendrimer surface and Congo red molecules. Thermodynamic parameters illustrate that the adsorption is endothermic and spontaneous. Findings suggest the Nanocomposites G-3PS G-5PS) are good adsorbents for the removal of Congo red dye from aqueous solutions.

The plastisphere is the microbial communities that grow on the surface of plastic debris, often used interchangeably with plastic biofilm or biofouled plastics. It can affect the properties of the plastic debris in multiple ways. This review aims to present the effects of the plastisphere on the physicochemical properties of microplastics systematically. It highlights that the plastisphere modifies the buoyancy and movement of microplastics by increasing their density, causing them to sink and settle out. Smaller and film microplastics are likely to settle sooner because of larger surface areas and higher rates of biofouling. Biofouled microplastics may show an oscillating movement in waterbodies when settling due to diurnal and seasonal changes in the growth of the plastisphere until they come close to the bottom of the waterbodies and are entrapped by sediments. The plastisphere enhances the adsorption of microplastics for metals and organic pollutants and shifts the adsorption mechanism from intraparticle diffusion to film diffusion. The plastisphere also increases surface roughness, reduces the pore size, and alters the overall charge of microplastics. Charge alteration is primarily attributed to changes in the functional groups on microplastic surfaces. The plastisphere introduces carbonyl, amine, amide, hydroxyl, and phosphoryl groups to microplastics, causing an increase in their surface hydrophilicity, which could alter their adsorption behaviors for heavy metals. The plastisphere may act as a reactive barrier that enhances the leaching of polar additives. It may anchor bacteria that can break down plastic additives, resulting in decreased crystallinity of microplastics. This review contributes to a better understanding of how the plastisphere alters the fate, transport, and environmental impacts of microplastics. It points to the possibility of engineering the plastisphere to improve microplastic biodegradation. Graphical abstract

Moringa oleifera (MO) seed coat, a postharvest waste of MO seed, was mercerized and used as eco-friendly adsorbent for removal of Congo red (CR) dye from aqueous solution at different time and temperature. Mercerized M. oleifera seed coat (MSC) was characterized through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) before and after adsorption process. Data obtained from effect of contact time on CR dye-uptake were applied on Elovich, pseudo-first- and second-order kinetic models, as well as on intraparticle diffusion and Boyd models. SEM and FTIR showed adsorption of CR dye on MSC through filled holes (SEM), appearance of new and shifting existing of functional groups (FTIR) on the surface of MSC after adsorption process. Adsorption kinetics was seen to be best fitted with pseudo-second-order model with the highest value of correlation coefficient at all temperatures. Film diffusion mechanism controlled the adsorption process, where external mass transfer was higher than internal mass transfer. Adsorption kinetics parameters confirmed removal of CR dye from aqueous solution through chemical and physical adsorption on MSC.

The study aimed to determine the nature of the kinetics of the manganese sorption process on Ukrainian tuff and basalt at different temperatures characteristic of the natural water environment. The scope of the research included manganese sorption kinetic test on natural mineral sorbents at temperatures of 10, 17.5 and 25 °C in slightly acidic conditions. Sorption (pseudo-first order, pseudo-second order and Elovich models) and diffusion kinetic models (liquid film diffusion and intraparticle diffusion) were used in the analysis of test results. The manganese sorption process on both tuff and basalt proceeded quickly. The dynamic equilibrium state of manganese sorption settled after 35 and 45 min on tuff and basalt respectively. Although the process took place in a slightly acidic environment and below pHPZC of the sorbents, possible electrostatic repulsion did not inhibit the removal of Mn. The Mn sorption on both materials followed the PSO kinetics model. Based on the diffusion kinetic models, it was determined that Mn sorption process on both materials was influenced by diffusion through the boundary layer and intraparticle diffusion. The differences in removal efficiency and rate of Mn sorption in the temperature range of 10–25 °C were not found.

Tetraethylenepentamine (TEPA)-based mesoporous MCM-41 is used as the adsorbent to determine the CO2 desorption kinetics of amine-modified materials after adsorption. The experimental data of CO2 desorption as a function of time are derived by zero-length column at different temperatures (35, 50, and 70 °C) and analyzed by Avrami’s fractional-order kinetic model. A new method is used to distinguish the physical desorption and chemical desorption performance of surface-modified mesoporous MCM-41. The activation energy Ea of CO2 physical desorption and chemical desorption calculated from Arrhenius equation are 15.86 kJ/mol and 57.15 kJ/mol, respectively. Furthermore, intraparticle diffusion and Boyd’s film models are selected to investigate the mechanism of CO2 desorption from MCM-41 and surface-modified MCM-41. For MCM-41, there are three rate-limiting steps during the desorption process. Film diffusion is more prominent for the CO2 desorption rates at low temperatures, and pore diffusion mainly governs the rate-limiting process under higher temperatures. Besides the surface reaction, the desorption process contains four rate-limiting steps on surface-modified MCM-41.

This study used colloidal lithography in conjunction with imprint lithography (embossing) to fabricate a light diffusion film based on the surface microstructure. An automated system was developed to arrange polystyrene (PS) spheres (diameter of 0.6 to 6 μm) on the substrate surface in a variety of configurations: single layer of spheres with constant diameter, single layer of spheres with multiple diameters, and double layer of spheres with multiple diameters. Optical diffusion testing revealed that PS spheres with a constant diameter created light patterns characterized by concentric circles induced by interference. PS spheres with multiple diameters were shown to reduce the interference. A double layer of spheres of various size presented the best optical diffusion performance. We reduced the effects of scattering between PS spheres through the use of embossing to duplicate the microstructure of the PS spheres, which resulted in outstanding diffusion performance with high transparency.

This study aims to develop efficient and sustainable hydrogels for dye adsorption, addressing the critical need for improved wastewater treatment methods. Carboxymethyl cellulose (CMC)-based hydrogels grafted with AAc were synthesized using gamma radiation polymerization. Various AAc to CMC ratios (5:5, 5:7.5, 5:10, 5:15) were treated with 37% NaOH and exposed to 1–15 kGy radiation, with the optimal hydrogel obtained at 5 kGy. Swelling studies showed an increase in swelling with 5–7.5% AAc content, with the 5:7.5 hydrogel achieving the highest swelling at 18,774.60 (g/g). FTIR spectroscopy confirmed the interaction between AAc and CMC, indicating the successful formation of the hydrogel. DSC analysis revealed that higher AAc content led to increased glass transition and decomposition temperatures, thereby enhancing thermal stability. The swelling kinetics were linked to a reduction in pore size and improved AAc grafting. The 5:7.5 hydrogel demonstrated the highest adsorption capacity (681 mg/g) for methylene blue at 80 mg/L, achieving a desorption efficiency of 95% in 2M HCl. Kinetic analysis revealed non-uniform physisorption on a heterogeneous surface, which followed Schott’s pseudo-second-order model. This study advances the development of efficient hydrogels for water purification, providing a cost-effective and environmentally friendly solution for large-scale applications.

To investigate the leaching rules and mechanism of a hard rock uranium ore, this paper conducted conventional leaching experiments based on the chemical composition and mineral occurrence status of the ore. Various factors affecting leaching were explored, and experimental data were fitted using the shrinking-core model. The results showed that uranium in the ore mainly existed in the form of pitchblende and coffinite, and the uranium grade of the sample was 0.15%. Under the leaching conditions of a temperature of 50 °C, a particle size of  − 100 mesh, an acid dosage of 32 kg t −1 , a pyrolusite dosage of 10 kg t −1 , a liquid–solid ratio of 1:1, and an 8 h duration, the leaching rate of the uranium ore reached 99.12%. The leaching process was controlled by solid film diffusion, and the apparent activation energy was 11.6 kJ mol −1 . Insoluble substances were present on the surface of the slag, and the solid film product was the main reason hindering leaching.

Activated carbon produced from fluted pumpkin ( Telfairia occidentalis ) seed shell was utilized for the removal of lead (II) ion from simulated wastewater. Adsorption tests were carried out in series of batch adsorption experiments. Several kinetic models (Bhattacharya-Venkobacher, Elovich, pseudo first and second order, intra-particle and film diffusion) were tasted for conformity to the experimental data obtained. The Langmuir and Freundlich adsorption models were also used to test the data. The amount of lead (II) ion adsorbed at equilibrium from a 200 mg/L solute concentration was 14.286 mg/g. The experimental data conform very well to the pseudo-second order equation where equilibrium adsorption capacities increased with increasing initial lead (II) concentration. The rate of the adsorption process was controlled by the film (boundary layer) diffusion as the film diffusion co-efficient values obtained from data analysis were of the order of 10 6 cm 2 /s. From the plots, the linear regression coefficient (R 2 ) of the Langmuir model was higher than that of the Freundlich: the adsorption isotherm obeyed the Langmuir model better than the Freundlich model.