Activated carbon with high surface area and abundant pore structure is widely used for contaminant adsorption in wastewater treatment. Rice husks (RHs) with unique composition and microstructure are often used as carbon source to prepare activated carbon. Herein, ultra-large specific surface area activated carbon was synthesized from rice husks with pre-activation and activation by supersaturated KOH solution at different temperatures. With the increase of activation temperature, the specific surface area and total pore volume of activated carbon gradually increase. The activated carbon obtained at 900 ℃ shows the largest specific surface area of 3600 m²/g and the maximal total pore volume of 3.164 cm³/g, which are significantly superior to those of the commercial activated carbon (YP-80, the specific surface area of 1310 m²/g and the total pore volume of 0.816 cm³/g, respectively). The highest maximum adsorption capacity for methylene blue was found for the activated carbon with the largest specific surface area, namely, 983 mg/g, which is almost twice as high as that of YP-80 (525 mg/g). By adsorption kinetics fitting, the results are consistent with pseudo-second-order model which indicates that the process of adsorbing methylene blue is chemical adsorption.

Phosphorus is an important nutrient element that affects the growth of algae. The sorption of phosphorus on the sediments plays an important role in its bio-geochemical cycle, with metal oxides such as alumina being one of the important active components for the process. The sorption behavior of phosphorus on two kinds of alumina (γ-Al₂O₃, amorphous alumina) was studied through batch methods. Both kinetics and thermodynamics of the process were investigated, as well as the effects of temperature, salinity, and pH of the medium on the process. The sorption kinetic curves could be described by a two-compartment first order equation, and the isotherms fit Freundlich equation well. The amorphous alumina has a larger specific surface area, and its sorption ability is stronger than that of γ-Al₂O₃. Based on the results of surface acid-base titration, the sorption behavior is also considered to be related to the surface acidity and alkalinity of the aluminum oxides. Compared with NaNO₃ medium, the sorption of phosphorus in seawater was weakened. The sorption capacity decreases with the increase of the ionic strength. pH significantly affected the sorption ability of the oxides with the maximum capacity at pH=5. Higher temperatures are favorable to the sorption progress, which is endothermic and spontaneous with entropy increasing. The difference in the thermodynamic parameters of the two alumina seemed unremarkable.

In this work, molecular dynamics (MD) simulations were applied to address the major concerns about the independent and competitive adsorption processes of phenolic organic pollutants (POPs) on the graphene oxide (GO) in aqueous solution. Phenol, α-naphthol and 4-octyl-phenol were adopted as representatives of POPs and their adsorption energies were calculated, which followed an order of 4-octyl-phenol (41.34 kJ/mol)>α-naphthol (33.23 kJ/mol)> phenol (19.31 kJ/mol). The simulation results showed that hydrophobic properties of POPs were recognized as the driving force for their adsorption behaviors. Moreover, van der Waals interaction, electrostatic interaction, as well as hydrogen bonds, may also improve the adsorption capacity of GO towards POPs. The competitive adsorption process revealed that in addition to the direct adsorption onto the GO surface, the molecular aggregation may be another indirect adsorption way existed in the mixed system. Understanding the interaction between GO and POPs in aqueous solution is critical to the design and application of graphene-based materials and our findings are believed to contribute further theoretical basis to the engineering treatment of POPs-containing waste water.

A low-cost oyster shell was carried to prepare biogenic calcium carbonate (bio-CaCO₃) to remediate Pb(II) and methyl orange (MO) from contaminated water. The morphology, composition and structure of the material were analyzed mainly by scanning electron microscope (SEM), thermogravimetric analysis (TGA), X-ray fluorescence (XRF). The adsorption of Pb(II) and MO by bio-CaCO₃ was studied by combining batch experiments and microstructure characterization. Batch sorption experiments showed that 45% MO was removed by bio-CaCO₃ (m_sorbent/V_solvent=0.2 g/L, [MO]_initial=60 mg/L). An obviously morphology change took place after MO adsorbed onto bio-CaCO₃. The maximum sorption capacity of bio-CaCO₃ for Pb(II) is 1775 mg/g (pH=5.0, T=298 K), which is higher than that of the traditional nanomaterials such as bentonite and activated carbon. The Pb(II) removal mechanism is expected to be CaCO₃+ Pb(II)→PbCO₃, where the ΔH ^θ, ΔS ^θ and ΔG ^θ of Pb(II) sorption by bio-CaCO₃ (pH=5.0, T=298K) are -7.64 kJ/mol, -17.92 J/(mol·K) and -2.30 kJ/mol, respectively. More regular products with quadrangular structure are formed after Pb(II) adsorption. The results highlight that the bio-CaCO₃ has a high Pb(II) and MO sorption efficiency, demonstrating that it is a promising adsorbent material in environmental pollution management.

Boron is an important micronutrient for plants, animals, and humans. However, high concentrations of boron are harmful to animals and plants. A magnesium-aluminum-cerium hydrotalcite (Mg-Al-Ce-HT) was successfully prepared by the co-precipitation method for boron removal. Different analyses were conducted to confirm the structure and characteristics of Mg-Al-Ce-HT. Adsorption efficiency of Mg-Al-Ce-HT was studied as a function of initial pH, amount of adsorbent, concentration of initial boric acid, and contact time. The pH of the solution had a negligible effect on boron sorption when pH was less than 8.0. However, the adsorption capacity decreased when the pH exceeded 8.0. The optimum amount of the adsorbent was 200 mg, and the maximum adsorption capacity was 32.52 mg·g ^-1. Boron removal reached equilibrium at 160 min. The thermodynamic parameters revealed that the adsorption was a non-spontaneous and endothermic process. The data fitted well with the Langmuir model, which indicated that the process involved monolayer adsorption.