A novel paraffin-based N/P controlled-release material for biostimulation of phenol biodegradation in groundwater.

To address the problem of the weak natural restoration ability of oligotrophic groundwater environments, a novel N/P controlled-release material (CRM) for biostimulation, prepared by an improved method, was developed. CRMs can encapsulate N and P (N/P) salts for sustained release in aquifers. Paraffin-based CRMs can be used to control N/P release rates by adjusting the particle size of CRMs and the mass ratio of the paraffin. The developed CRMs had a more remarkable adaptability to groundwater than other materials. Specifically, 0.4-cm CRMs released N/P stably and efficiently over a wide temperature range (7-25 â„ƒ), and the release properties of various CRMs were not affected by pH. The release of N/P followed Fickian diffusion, and a dissolution-diffusion model was established to elucidate the mechanism of the controlled release. In contrast to bare N/P, CRMs obviously enhanced the biodegradation rate of phenol and prolonged the effectiveness of supplying N/P. The degradation rate of phenol in the CRM system increased by 20.8 %. The different supply modes of N/P, CRMs and bare N/P, resulted in differences in salinity. Metagenomic analysis showed that this difference changed the proportion of various phenol-degrading genera and thus changed the abundance of genes associated with the phenol degradation pathway.

One-step synthesis of Fe2O3 nano-rod modified reduced graphene oxide composites for effective Cr(vi) removal: removal capability and mechanism.

Reduced graphene oxide (rGO) supported Fe2O3 nanorod composites were prepared via a one-step hydrothermal method and further utilized for hexavalent chromium (Cr(vi)) removal from aqueous environments. The composite material exhibited an excellent removal efficiency for chromium (47.28 mg L-1), which was attributed to the electrostatic attraction and chemical reduction of chromium by the material. The removal mechanism was studied by SEM, BET, XPS, and FTIR. The results demonstrated that rGO was successfully modified by Fe2O3 nanorods (approximately 50 nm wide). Compared with graphene oxide (GO), the compound was much more easily separated from the solution after completing the removal. Furthermore, XPS characterization showed that Cr(vi) could also be reduced to low-toxicity Cr(iii) by hydroxyl groups. In the variables test, it was found that the removal process was pH-dependent. The results of the designed experiments for exploring the adsorption kinetics, isotherms and thermodynamics indicated that the removal process obeyed a pseudo-second-order kinetics model, Langmuir isotherm model and that it was a spontaneous exothermal process. This study provides the possibility of hydrothermal synthesis of Fe2O3/rGO for use as an excellent material to remove Cr(vi) from aqueous environments.