Bio-immobilization and recovery of chromium using a denitrifying biofilm system: Identification of reaction zone, binding forms and end products.

Chromium is an important resource in strategic metals. Different from most studies focusing on the bio-reduction of hexavalent chromium [Cr(VI)], this study aims to achieve the immobilization and recovery of chromium using a sequencing batch biofilm reactor. Results showed that Cr(VI) removal efficiency remained more than 99%, and 97% of reduced Cr(III) was immobilized in the biofilm. Immobilization zone, chromium forms and extracellular polymeric substances composition changes were combined to reveal the mechanism of Cr(VI) reduction and immobilization. The chromium distribution in biofilm demonstrated that intercellular layer was the main active zone with an immobilization amount of 891.70±126.32 mg/g-VSS. The reduced products analysis confirmed that trivalent chromium [Cr(III)] chelated with carboxyl, amino and other functional groups and immobilized in the form of organic Cr(III). The digestion method realized a chromium recovery efficiency of 74.59%. This study provides an alternative method for the bioremediation and resources recovery in chromium polluted wastewater.

Fabrication of Pd/Sludge-biochar electrode with high electrochemical activity on reductive degradation of 4-chlorophenol in wastewater.

Effective treatment and utilization of sludge contribute to achieve conventional carbon emission reduction and resource recovery, which is of great significance to realize carbon neutralization of WWTPs. Sludge carbonization derived biochar has attracted more interest because of high potential as catalytic materials. Therein, sludge-derived electrode exhibits a promising potential in the case of sludge utilization for electrocatalysis, however, electrocatalytic performance of the already reported sludge-derived electrode is unsatisfactory due to insufficient active sites. In this study, an efficient Pd/sludge-biochar loaded foam nickel (Pd-SAC@Ni) was successfully fabricated using simple pyrolysis and solidification method, and exhibited remarkable electrocatalytic performance for 4-chlorophenol (4-CP) degradation. Furthermore, the morphology, element distribution and crystal composition were characterized by SEM, EDS, XPS and XRD. The Pd-SAC@Ni electrode exhibited superior electrocatalytic performance than Ni, SAC@Ni, Pd-Ni electrodes. The reduction rate of 98.9% was achieved at current density of 5 mA cm-2, 4-CP concentration of 0.8 mM and initial pH of 7.0. Also, Pd-SAC@Ni electrode showed desirable reusability and achieved 98% of 4-CP removal after multiple runs of experiments. Moreover, the active hydrogen species (H*) generation capacity of electrodes was determined using tert-butanol (TBA) as trapping agent. The mechanism analysis demonstrated that direct reduction process and indirect reduction process both involved in the 4-CP degradation process, and their contribution were 19.5% and 80.5%, respectively. Then, the intermediates formed in the electrochemical degradation of 4-CP were revealed by HPLC and the plausible degradation pathway was proposed. This study provides a cost-effective approach for preparing sludge biochar electrode, and explored a novel way to promote resourceful utilization of sludge for carbon neutrality.

Competitive adsorption of sulfamethoxazole and bisphenol A on magnetic biochar: Mechanism and site energy distribution.

Competitive adsorption and complementary adsorption between emerging pollutants has been observed in multiple studies. Investigation of the preference of pollutants for different types of adsorption sites can provide a supplementary perspective for understanding complementary adsorption. In this study, the simultaneous adsorption of two typical emerging pollutants, sulfamethoxazole (SMX) and bisphenol A (BPA), on magnetic biochar (MBC-1) was investigated. The results showed that the modification with ferric chloride optimized the surface properties of biochar (aromaticity, hydrophobicity, and oxygen-containing functional groups, etc.), and helped to remove SMX and BPA through various interactions. The equilibrium adsorption capacity of the two adsorbents was inhibited by competitive adsorption in the mixed solute systems, which was due to the same adsorption mechanism. When pH = 7, the SMX and BPA adsorption mainly involved pore filling, hydrophobic effect, π-π EDA, and hydrogen bonding. In addition, electrostatic force, surface coordination, and ion exchange have also been proven to be related to the adsorption of SMX and BPA. In the co-adsorption system, BPA's competitive advantage might be due to its superior hydrophobicity, charge property, and molecular diameter. In the competitive adsorption experiment, the total adsorption capacity (Qi) of the competitive solute exceeded the adsorption inhibition (△Qi) of the main solute, indicating that the two solutes occupied their preferred adsorption sites, which confirmed the complementary adsorption phenomenon. Complementary adsorption can be explained by the preference of SMX and BPA for different types of adsorption sites. BPA preferentially occupied high-energy sites in the co-adsorption system, such as π-π EDA interaction, ion exchange, and surface coordination. At the same time, SMX tended to be removed by hydrophobic interaction and hydrogen bonding.

Identification and expression analysis of two zebrafish E2F5 genes during oogenesis and development.

During the process of screening genes that are preferentially expressed in zebrafish germ cells, we isolated an E2F family member zE2F5b, which is a truncated isoform of zebrafish E2F5a. The E2F transcription factors are thought to play an essential role in cell cycle progression. Reverse transcription polymerase chain reaction and whole mount in situ hybridization analyses have demonstrated that both zE2F5a and zE2F5b mRNAs are predominantly expressed in stage I and II oocytes. In early development, the two zE2F5 transcripts are expressed by many parts of the embryo and are then restricted to the brain area. Interestingly, zE2F5b mRNA is detected later in the lens and optic tectum while zE2F5a mRNA is absent. Our data suggests that E2F5 may play important roles in zebrafish brain, eye and ovarian development.

Identification of zRAP55,a gene preponderantly expressed in Stages I and II oocytes of zebrafish.

In an in silico search for gonand specific expressed genes, we have identified zRAP55 which is enriched in the ovary of zebrafish . zRAP55 encodes a protein of 382 amino acids with a highly conserved Lsm domain. zRAP55 protein shares more than 56% identities with that of other vertebrate species. RT-PCR results show that it is predominantly expressed in the ovary. In situ hybridization and immunohistochemistry studies reveal that zRAP55 is ubiquitously dispersed throughout the cytoplasm of stages I and II oocytes, whereas no expression is observed in stages III and IV oocytes. As an RNA associated protein, zRAP55 might function in the control of protein translation at the early stages of oogenesis in zebrafish.