Kinetics and Size Effects on Adsorption of Cu(II), Cr(III), and Pb(II) Onto Polyethylene, Polypropylene, and Polyethylene Terephthalate Microplastic Particles

Due to its small size, large specific surface area and hydrophobicity, microplastics, and the adsorbed contaminants may together cause potential negative effects on ecosystems and human beings. In this study, kinetics and size effects on adsorption of Cu(II), Cr(III), and Pb(II) onto PE, PP and PET microplastic particles were explored. Results indicated that the PE and PET microplastics have the higher adsorption capacity for Cu(II), Cr(III), and Pb(II) than that for PP microplastic. The adsorption capacity was affected by microplastic types and metal species. Among the three metals, Pb(II) had the largest adsorption amount on microplastic particles, especially on PET particles. Moreover, the adsorption capacities of microplastics increase with the decrease of particle size. The metal adsorption capacity of <0.9 mm microplastics is greater than that of 0.9–2 mm and 2–5 mm microplastics. The size effect on metal adsorption was largest for PE microplastic. More attention should be paid in case of the coexistence of heavy metals and tiny PE and PET microplastics in the environment.

Adsorption Performance of Human-like Collagen by Alkali-modified Kapok Fiber: A Kinetic, Equilibrium, and Mechanistic Investigation

Collagen-based dressings achieve excellent repair of the skin during metical cosmetology, which has received a lot of attention recently. Although great progress has been made on using biomass fiber as dressing carrier, more research is required on developing novel biomass fibers because of the limitations of (i.e., high cost and complex processing) of existing materials. In this study, the adsorption behaviors of two human-like collagen were studied by examining the Kapok fiber that was modified using alkali consisting of various amounts of the mass fraction. Results show that the alkali-modified Kapok fiber surface becomes rough with vertically arranged grooves, and the cross-section depicts the hollow cavity structure. The composition analysis of alkali modified Kapok shows that alkali dissolves part of the hemicellulose and lignin. Additionally, the surface energy rises sharply and the water contact angle changed from hydrophobic to hydrophilic. The adsorption amount of raw Kapok fiber is around 0.6g/g, which accounts for only one twenty-first of the adsorption amount of alkali-treated Kapok (around 12.6g/g), while the equilibrium adsorption amount was not sensitive to alkali concentration. The kinetics of human-like collagen followed both Quasi first and Quasi second order kinetic model, implying that the adsorption process where characterized by both physisorption and chemisorption. Finally, characterization of the AKF-2 coupled with the studies based on the inter-particle diffusion model showed a three-step of human-like collagen diffusion consisting of surface diffusion, inter-fiber diffusion and fiber' hollow cavity diffusion. Our results demonstrate a perfect high absorption performance of Kapok fiber providing a potential for application of collagen-base dressings.

Synthesis and Characterization of an Amphoteric Asphalt Emulsifier

A novel amphoteric asphalt emulsifier of octadecylbis(propanamide)-(3’-sodium phosphate-2’-hydroxypropyl)ammonium chloride was synthesised from the raw materials octadecylamine, acrylamide, epichlorohydrin and sodium dihydrogen phosphate. The tertiary amine octadecyl-bis(propanamide) was synthesised from octadecylamine and acrylamide (step 1). Sodium 3-chloro-2-hydroxypropyl phosphate (intermediate) was obtained from epichlorohydrin and sodium dihydrogen phosphate (step 2). The asphalt emulsifier was obtained from octadecyl-bis(propanamide)-tertiary amine and the intermediate by quaternisation reaction (step 3). The yield of the final product reached 94.90%. The structure was identified by FTIR, 1H-NMR and elemental analysis. The critical micelle concentration of the product is 1.46 × 10–5 mol L–1. The surface tension at CMC is 37.78 mN ν–1. The saturated adsorption amount of asphalt emulsifier is 2.72 × 10–3 mmol ν–2. The occupied area per asphalt emulsifier molecule at CMC is 0.611 nm2 mol–1. The surfactant is a fast-setting asphalt emulsifier.

Removal of Cd2+ from Water Containing Ca2+, Mg2+ using Titanate Nanotubes Modified by Carbon

Ca2+ and Mg2+ usually exist in natural water. When Cd2+ is removed from water by adsorption, it will be inhibited by these two ions. Titanate nanotubes (TNTs) have an effective adsorption capacity for Cd2+ due to extraordinary ion-exchange property. However, TNTs also adsorb Ca2+ and Mg2+ in water. In this study, carbon-modified TNT (TNT/C or TNT/HC) was synthesized by hydrothermal synthesis. The transmission electron microscope (TEM) images show that TNT/C or TNT/HC still keep nanotube morphology. The experimental results show the order of adsorption amount to Cd2+ is TNT > TNT/C > TNT/HC when there is no Ca2+ or Mg2+. But when there is Ca2+ or Mg2+ in the water, the order of Cd2+ adsorption capacity becomes TNT/HC > TNT/C > TNT. It indicates that the surface carbon-modification can alleviate the hindrance of Ca2+ or Mg2+ to Cd2+ removal. This is because the carbon on the surface of TNT captured part of Ca2+ or Mg2+, it made more Cd2+ be successfully absorbed by TNT through ion exchange. This mechanism was confirmed by XPS spectra analysis. The results of this paper can provide ideas for the adsorption and removal of Cd2+ in water in the presence of Ca2+ or Mg2+.

Nitrogen Recovery from Clear-Cut Forest Runoff Using Biochar: Adsorption–Desorption Dynamics Affected by Water Nitrogen Concentration

Forest regeneration operations increase the concentration of nitrogen (N) in watercourses especially outside the growing season when traditional biological water protection methods are inefficient. Biochar adsorption-based water treatment could be a solution for nutrient retention. We studied the total nitrogen (TN) and nitrate–nitrogen (NO3−–N) adsorption–desorption properties of spruce and birch biochar. The adsorption test was performed under four different initial concentrations of TN (1, 2, 3, and 4 mg L−1) using forest runoff water collected from ditch drains of boreal harvested peatland. The results showed that the TN adsorption amount increased linearly from the lowest to the highest concentration. The maximum adsorption capacity was 2.4 and 3.2 times greater in the highest concentration (4 mg L−1) compared to the lowest concentration (1 mg L−1) in spruce and birch biochar, respectively. The NO3−–N adsorption amount of birch biochar increased linearly from 0 to 0.15 mg NO3−–N g biochar−1 when the initial concentration of NO3−–N increased from 0.2 to 1.4 mg L−1. However, in spruce biochar, the initial concentration did not affect NO3−–N adsorption amount. The results indicate that concentration significantly affects the biochar’s capacity to adsorb N from water. The desorption test was performed by adding biochar extracted from the adsorption test into the forest runoff water with low TN concentration (0.2 or 0.35 mg L−1). The desorption results showed that desorption was negligibly small, and it was dependent on the TN concentration for birch biochar. Therefore, biochar can be a complementary method supporting water purification in peatland areas.

Understanding the Adsorption of Peptides and Proteins onto PEGylated Gold Nanoparticles

Polyethylene glycol (PEG) surface conjugations are widely employed to render passivating properties to nanoparticles in biological applications. The benefits of surface passivation by PEG are reduced protein adsorption, diminished non-specific interactions, and improvement in pharmacokinetics. However, the limitations of PEG passivation remain an active area of research, and recent examples from the literature demonstrate how PEG passivation can fail. Here, we study the adsorption amount of biomolecules to PEGylated gold nanoparticles (AuNPs), focusing on how different protein properties influence binding. The AuNPs are PEGylated with three different sizes of conjugated PEG chains, and we examine interactions with proteins of different sizes, charges, and surface cysteine content. The experiments are carried out in vitro at physiologically relevant timescales to obtain the adsorption amounts and rates of each biomolecule on AuNP-PEGs of varying compositions. Our findings are relevant in understanding how protein size and the surface cysteine content affect binding, and our work reveals that cysteine residues can dramatically increase adsorption rates on PEGylated AuNPs. Moreover, shorter chain PEG molecules passivate the AuNP surface more effectively against all protein types.

Synthesis of Comb-Polyurethane-Modified Polycarboxylate at Indoor Temperature and Its Interaction With Portland Cement

According to the principle of radical polymerization reaction, different polycarboxylates with comb structures were synthesized. With the other two commercial polycarboxylates (C-PCE-1 and C-PCE-2), the effects of all the polycarboxylates on adsorption, hydration, zeta potential, liquid surface tension, and flowability in Portland cement were determined. Compared to O-PCE and C-PCEs, the adsorption value of M-PCE increased by 14.1% and the adsorption rate increased by 24% maximum. O-PCE, C-PCE-1, and C-PCE-2 have a delayed effect on the hydration of the cementitious materials, but M-PCE does not. Due to higher adsorption amount, M-PCE with siloxane groups has an excellent comprehensive performance of zeta potential, liquid surface tension, and flowability in cementitious materials.

Effects of PCE on the Dispersion of Cement Particles and Initial Hydration

The effects of polycarboxylate superplasticizers (PCEs) on the dispersing properties and initial hydration of cement particles with various water-to-cement (w/c) ratios was investigated, including the water film thickness (WFT), rheology, fluidity, adsorption of PCEs, zeta potential, degree of hydration, hydration products. The experimental results demonstrate that the initial rheological and fluidity parameters were more sensitive to the PCE dosage at a lower w/c because the WFT and the zeta potential on cement particles change more significantly. Moreover, the higher adsorption amounts of the PCEs at a lower w/c lead to a stronger inhibition of the initial hydration, whilst, at the same PCE dosage, the cement pastes have a more rapid fluidity loss and quicker hydration reactions at a higher w/c due to a lower adsorption amount of the PCE on cement particles.

Study on the adsorption of heavy metal ions Pb2+, Zn2+, Co2+, Ni2+from the aqueous solution of the copolymer prepared by gamma induced radiationpolymerization

Copolymer hydrogel (PVA-g-AA) having varied PVA (Polyvinyl alcohol) and AA (Acrylic acid) content is prepared by gamma induced radiation polymerization. The parameters affecting the gel fraction yield have been studied. The gel fraction and the swelling property are found to be 92.39 and 905% respectively at an absorbed dose of 20 kGy. Structural and property characteristics were determined by Fourier Transform Infrared (FTIR) spectrometer and Differential Scanning Calorimetry (DSC). The surface morphology of PVA and copolymer has been studied with Scanning Electron Microscope (SEM). The factors affecting the metal uptake such as pH, time, and initial feed metal concentration were investigated. It is found that at pH 5 and after 240 minutes the maximum adsorption amount are 178, 161, 117, and 110 mg/g for Pb2+, Zn2+, Co2+, and Ni2+ respectively.