Coadsorption behaviors and mechanisms of Pb(ii) and methylene blue onto a biodegradable multi-functional adsorbent with temperature-tunable selectivity

Sodium Percarbonate Activation by Plasma-Generated Ozone for Catalytic Degradation of Dye Wastewater: Role of Active Species and Degradation Process

In this paper, sodium percarbonate (SPC) was activated by ozone (O3) from plasma for catalytic treatment of dye wastewater. Methyl blue (MB), a typical industrial dye, was selected as the target dye contaminant. Results showed that enhancing O3 dosage and reducing MB concentration were beneficial to MB degradation. Compared to acid condition, a higher removal efficiency of MB was obtained in alkaline condition. With an increase of SPC dosage, the removal efficiency of MB first was raised, and then it declined. Under the optimal dosage of 50 mg/L, the removal efficiency of MB reached 85.7% with 30 min treatment time. The energy efficiency was improved from 5.21 g/kWh to 5.71 g/kWh. A synergetic effect can be established between O3 and SPC. Radical capture experiments verified that ·OH, ·O2−, 1O2, and ·CO3− played important parts in MB degradation. With increasing reaction time, the amount of total organic carbon (TOC) declined and the amount of ammonia nitrogen (NH3-N) increased. The addition of SPC enhanced the solution’s pH value and conductivity. The degradation pathway was proposed based on density functional theory (DFT) analysis and relevant literatures. The toxicity of MB was alleviated after O3/SPC treatment. The O3/SPC process was also suitable for the treatment of other dyes and actual wastewater.

Removal of lead from aqueous solutions using three biosorbents of aquatic origin with the emphasis on the affective factors

The biosorptive potentials of three aquatics-based biosorbents, including shells of a bivalve mollusk and scales of two fish species for Pb removal from aqueous solutions were evaluated, for the first time. A Box-Behnken design with the response surface methodology was used to investigate the effects of the seven important variables (contact time, temperature, initial concentration, dosage, size, salinity and pH) on the sorption capacity of the sorbents. Among the seven studied factors, the effects of biosorbent dosage, initial concentration and pH were significant for all the response variables, while biosorbent size was not significant for any of the responses. The initial concentration was the most influential factor. The presence of Pb ions on the surfaces of the biosorbents after the adsorption was clearly confirmed by the SEM-EDX and XRF analyses. The maximum sorption capacities of the biosorbents were comparable to the literature and the descending order was as follows: scales of Rutilus kutum and Oncorhynchus mykiss and the shells of Cerastoderma glaucum. The isotherm studies revealed Langmuir model applicability for the Pb adsorption by R. kutum and O. mykiss scales, while Freundlich model was fitted to the adsorption C. glaucum shells.