Investigation on the mechanism of water activated via tourmaline powder

Rapid enrichment of AnAOB with a novel vermiculite/tourmaline modification technology for enhanced DEAMOX process

The DEnitrifying AMmonium OXidation (DEAMOX) has been proven to be a promising process treating contaminated surface water containing ammonia and nitrate, while the enrichment of the slow-growing anammox bacteria (AnAOB) remains a challenge. In this study, a novel polyurethane-adhesion vermiculite/tourmaline (VTP) modified carrier was developed to achieve effective enrichment of AnAOB. The results demonstrated that the VTP-1 (vermiculite: tourmaline = 1:1) system exhibited the greatest performance with the total nitrogen removal efficiency reaching 87.6% and anammox contributing 63% to nitrogen removal. Scanning electron microscope analysis revealed the superior biofilm structure of the VTP-1 carrier, providing attachment for AnAOB. The addition of VTP-1 promoted the secretion of EPS (extracellular polymeric substances) by microorganisms, which increased to 85.34 mg/g VSS, contributing to the aggregation of anammox cells. The favorable substrate microenvironment created by NH4+ adsorption and NO2- supply via partial denitrification process facilitated the growth of AnAOB. The relative abundance of Candidatus Brocadia and Thauera increased from 0.04% to 0.3%-1.03% and 2.06% in the VTP-1 system, respectively. This study sheds new light on the anammox biofilm formation and provides a valid approach to initiate the DEAMOX process for low nitrogen polluted water treatment.

Tourmaline guiding the electric field and dechlorination pathway of 2,3-dichlorophenol by Desulfitobacterium hafniense

The dehalogenation of organohalides has been a research hotspot in bioremediation field; however, the influence of tourmaline, a natural ore that can generate spontaneous electric field, on organohalide-respiring bacteria (OHRB) and their dechlorination process is not well known. In this study, the effect and mechanism of tourmaline on the reductive dechlorination of 2,3-dichlorophenol (2,3-DCP) by Desulfitobacterium hafniense DCB-2T were explored. The characterization results confirmed that tourmaline had good stability and the optimal dosage of tourmaline was 2.5 g/L, which shortened the total time required for dechlorination reaction to 72 hr. Besides, tourmaline amendment also increased the proportion of 2-chlorophenol (2-CP) from 18% to 30% of end products, while that of 3-CP decreased correspondingly. The theoretical calculations showed that the bond charge of the ortho-substituted chlorine declined from -0.179 to -0.067, and that of meta-substituted chlorine increased from -0.111 to -0.129, which indicated that the spontaneous electric field of tourmaline affected the charge distribution of 2,3-DCP and was more conducive to the generation of 2-CP. Overall, tourmaline with the spontaneous electric field affected the reductive dechlorination pathway of Desulfitobacterium,and the tourmaline-OHRB combining system might serve as a novel strategy for the bioremediation of environments polluted with chlorinated phenols.

Biofilm carriers for anaerobic ammonium oxidation: Mechanisms, applications, and roles in mainstream systems

The anaerobic ammonium oxidation (ANAMMOX) process was proposed as the most promising nitrogen removal process. Biofilm carriers were demonstrated to effectively enhance the anaerobic ammonium oxidating bacteria (AnAOB) retention. This paper reviews the effect of carrier properties on the AnAOB biofilm development according to the biofilm development process and the application state-of-art of three major kinds of conventional carriers, organic-based, inorganic-based carriers, and gel carriers, from the view of system performance and functional microorganisms. The carrier modification methods and purpose are thoroughly summarized and classified into three categories corresponding to various carrier defects. Four important aspects of the desirable carrier for the mainstream ANAMMOX process were proposed, including providing spatial configuration, enhancing the biomass retention, reinforcing the activity, and improving the growth environment, which needs to combine the advantages of organic and inorganic materials. Eventually, the future application directions of novel carriers for the ANAMMOX-based process were also highlighted.

Well-designed internal electric field from nano-ferroelectrics promotes formic acid oxidation on Pd

Pd-Based catalysts are considered the most efficient catalysts in direct formic acid fuel cells. However, the poisoning and dissolution of Pd in acidic systems limit its commercialization. Here, we propose an all-in-one solution for the anti-dissolution and anti-poisoning properties of palladium. A novel structured catalyst, Pd nanoparticles embedded in a carbon layer internally decorated with tourmaline nanoparticles (TNPs), is proposed for formic acid oxidation (FAO). The internal electric field strength of the catalysts is readily regulated by controlling the amount of TNPs. Remarkably, the prepared catalyst exhibits as high as 3.9 times mass activity (905 A g^-1) compared with the commercial Pd/C catalyst. The significant improvement in the electrocatalytic performance of the catalyst is mainly due to the polarized electric field of TNPs causing charge transfer from Pd to tourmaline, which weakens the O-H bond of HCOOH and the bond between Pd and CO_ad. Another advantage brought by the internal polarized electric field is that it facilitates water dissociation to produce OH_ad, thereby improving the anti-poisoning ability of the catalyst in acidic media. Moreover, the firmly anchored Pd nanoparticles can avoid dissolution and agglomeration during long-term use. 80.2% mass activity remained after the accelerated durability test.