Optimizing the added ratio of mixed auxiliary packings for enhancing the biological vanadium (V) removal

Surface Hydroxyl Groups Functionalized Porous CeO2 for Enhanced Selective Adsorption of As(III)

The adsorption technique has been considered as one of the promising methods to remove arsenic ions in aqueous systems. However, the adsorbents are usually poorly selective and have low capacity. Herein, a kind of porous CeO2 containing surface hydroxyl group which synthesized facilely possesses the great performance of selective adsorption of As(III) with 98.57% removal against 14 other coexisting metal ions. The results showed that the processes of As(III) and As(V) uptake were heterogeneous monolayer adsorptions and included external and intraparticle diffusions. The adsorption capacities at pH 2.5 reached 111.24 and 56.89 mg/g for As(III) and As(V), respectively. In addition, it also showed that As(III) could be oxidized to As(V) in the adsorption process. Density functional theory calculations revealed that the OH group in H3AsO30 and the As atom in H3AsO40 have affinity with lattice oxygen (O2-) in CeO2, while the O atom in H2AsO4- preferred the Ce atom in CeO2. This study provides a novel porous CeO2 containing hydroxyl groups for selective and efficient removal of arsenic and elucidates the mechanism of As(III) and As(V) adsorptions.

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 ℃), 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.

Performance of a continuous flow reactor on bio-reducing vanadium with straw

Vanadium (V) in groundwater could cause a serious threat to the environment and health. Continuous flow reactors were applied to reduce V(V) with straw being a solid carbon. The reduced efficiency of V(V) in the reactor with straw and inoculated sludge reached to 71.8%-99.9% for two months' operation (after 44 d). However, a long-term operation with only straw was not satisfied, achieving the reduced efficiency of 39.2-66.6%. The SEM images clearly revealed some traces of straw surface by utilized by microbes, which implied that microbes had a stronger capacity to hydrolyze straw. The introducing external microbes were essential to achieve a better bio-reduction performance on V(V). Treponema (5.3%) with metal reduction ability and Prevotellaceae (3.3%) able to specifically degrade complex plant-derived polysaccharides were found to be dominant in the microbial community. Utilizing agricultural biomass can save a lot of normal carbon like acetate, which is of benefit for carbon emissions.