A nappies management by-product for the treatment of uranium-contaminated waters.

The direct disposal of municipal solid waste such as nappies to the environment may create serious pollution problems. Based on the circular economy and waste management concepts, the conversion of nappies and/or their ingredients (such as super absorbent polymer (SAP)) to high added value products is of great importance. In this work, a modified SAP (MSAP) was examined as an adsorbent for treatment of contaminated waters and uranium recovery. Batch experiments and spectroscopic techniques were used to examine the effect of various parameters (pH, contact time, temperature, initial concentration, and ionic strength), and the mechanism of adsorption U(VI) and desorption process. The U(VI) concentration was determined by alpha spectroscopy after addition of 232U standard tracer solution to account for possible interferences during electrodeposition and alpha particle counting. The maximum adsorption monolayer capacity was found to be 217.4 mg/g at pH 4.0 and at 298 K. The adsorption of U(VI) on MSAP seems to occur mainly via the formation of inner-sphere surface complexes between U(VI) and the carboxylic surface moieties of MSAP. The MSAP could satisfactorily be regenerated with 0.1 M Na2CO3 (>90%) and it also shows a promising applicability to real wastewaters contaminated with U(VI).

Performance of aquatic weed - Waste Myriophyllum spicatum immobilized in alginate beads for the removal of Pb(II).

A new biosorbent - alginate encapsulated with Myriophyllum spicatum - MsA was investigated for lead ions removal. This biosorbent was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), zeta potential, X ray Diffraction (XRD) and size distribution analysis. FT-IR analysis demonstrated that the lead ions sequestration mechanism included ion exchange and lead complexation with the carboxyl, carbonyl and hydroxyl groups in MsA. In order to better understand the mechanisms of the binding of Pb(II) on immobilized M. spicatum beads, 3 reaction and one diffusion based kinetic models were applied on kinetic data removal lead ions on three materials: M. spicatum, Ca-alginate and MsA. Myriophyllum spicatum encapsulated with alginate - MsA have higher adsorption capacity than M. spicatum. Among examined six isotherms Redlich-Peterson and the Langmuir isotherm model exhibited the best fit to the experimental data, with capacities ranging from 230 to 268.7 mg/g. Among the various tested desorption agents, nitric acid has proven to be the best. The obtained results suggest that the immobilized M. spicatum biosorbent holds great potential for lead wastewater treatment applications.

Efficient mercury removal from wastewater by pistachio wood wastes-derived activated carbon prepared by chemical activation using a novel activating agent.

Ammonium nitrate (NH4NO3) with explosive characteristics at high temperatures was used as a novel activating reagent to prepare a surface-engineered activated carbon derived from pistachio wood wastes (PWAC). PWAC was characterized and compared with commercial activated carbon (CAC) by textural and morphological properties, surface chemistry, crystal structure, and surface elemental composition. The results indicated that the optimal conditions of PWAC preparation to obtain the highest mercury adsorption capacity were pyrolysis temperature (800 °C), pyrolysis time (2 h), and impregnation ratio (5%). PWAC was of highly regular-shaped and well-developed pores and possessed a large surface area (1448 m2/g) and high total pore volume (0.901 cm3/g). The batch experiments indicated that the adsorption process of Hg(II) was strongly dependent on the solution pH and reached fast equilibrium at approximately 30 min. PWAC (202 mg/g) exhibited a significantly higher maximum adsorption capacity than commercial activated carbon (66.5 mg/g). Adsorbent-adsorbate dispersion interaction plays a major role in the adsorption mechanism, compared to the minor role played by pore filling and reduction mechanism. Overall, ammonium nitrate can be considered a newer activating reagent to prepare promising and low-cost PWAC for effectively Hg(II) removal from water media.