Research Highlights

Involved Members: Dr. James Kar Hei FANG, Prof. Paul Kwan Sing LAM Plastic waste are introduced into the environment inevitably and their exposure in the environment causes deterioration in mechanical and physicochemical properties and leads to the formation of plastic fragments, which are considered as microplastics when their size is < 5="" mm.="" in="" recent="" years,="" microplastic="" pollution="" has="" been="" reported="" in="" all="" kinds="" of="" environments="" worldwide="" and="" is="" considered="" a="" potential="" threat="" to="" the="" health="" of="" ecosystems="" and="" humans.="" in="" this="" review,="" potential="" hotspots="" for="" the="" accumulation="" of="" plastic="" waste="" were="" identified,="" major="" mechanisms="" and="" characterization="" methods="" of="" plastic="" degradation="" were="" summarized,="" and="" studies="" on="" the="" environmental="" degradation="" of="" plastics="" were="" evaluated.="" formation="" and="" degradation="" of="" microplastics,="" including="" nanoplastics,="" should="" receive="" more="" research="" attention="" to="" assess="" their="" fate="" and="" ecological="" risks="" in="" the="" environment="" more="" comprehensively.="" reference:="" zhang,="" k.,="" hamidian,="" a.h.,="" tubić,="" a.,="" zhang,="" y.,="" fang,="" j.k.h.,="" wu,="" c.="" &="" lam,="" p.k.s.="" (2021).="" understanding="" plastic="" degradation="" and="" microplastic="" formation="" in="" the="" environment:="" a="" review.="" environmental="" pollution,="" 274,="" 116554.="" 5="" mm.="" in="" recent="" years,="" microplastic="" pollution="" has="" been="" reported="" in="" all="" kinds="" of="" environments="" worldwide="" and="" is="" considered="" a="" potential="" threat="" to="" the="" health="" of="" ecosystems="" and="" humans.="" in="" this="" review,="" potential="" hotspots="" for="" the="" accumulation="" of="" plastic="" waste="" were="" identified,="" major="" mechanisms="" and="" characterization="" methods="" of="" plastic="" degradation="" were="" summarized,="" and="" studies="" on="" the="" environmental="" degradation="" of="" plastics="" were="" evaluated.="" formation="" and="" degradation="" of="" microplastics,="" including="" nanoplastics,="" should="" receive="" more="" research="" attention="" to="" assess="" their="" fate="" and="" ecological="" risks="" in="" the="" environment="" more="" comprehensively.="" reference:="" zhang,="" k.,="" hamidian,="" a.h.,="" tubić,="" a.,="" zhang,="" y.,="" fang,="" j.k.h.,="" wu,="" c.="" &="" lam,="" p.k.s.="" (2021).="" understanding="" plastic="" degradation="" and="" microplastic="" formation="" in="" the="" environment:="" a="" review.="" environmental="" pollution,="" 274,="">

Involved Members: Prof. Kenneth Mei Yee LEUNG, Prof. Xiaoyan LI Current toxicity assessment of zinc oxide nanoparticles (ZnO-NPs) seldom considers the impacts of surface modification while it is a common practice in commercial products. Therefore, we evaluated the toxicities of ZnO-NPs with three different silane coatings towards a marine copepod, Tigriopus japonicus. ZnO-NPs with more hydrophilic coatings were found consistently more toxic than the hydrophobic one, likely because the coatings could affect agglomeration and ion dissolution of ZnO-NPs, eventually increasing their bioaccumulation and toxicity. The meta-analysis further suggested that the toxicity of coated nanoparticle could be predicted by the hydrophobicity and density of their surface coatings. These findings will be beneficial to the future development of eco-friendly nanoparticles by surface modification. Reference: Lai, R.W.S., Kang, H.M., Zhou, G.J., Yung, M.M.N., He, Y.L., Ng, A.M.C., Li, X.Y., Djurišić, A.B., Lee, J.S. & Leung, K.M.Y. (2021). Hydrophobic surface coating can reduce toxicity of zinc oxide nanoparticles to the marine copepod Tigriopus japonicus. Environmental Science & Technology, 55, 6917-6925.  

Involved Member: Dr. Ruquan YE A review paper has summarized recent research progress in the modification of MnO2 single species by morphology control, structure construction, facet engineering, and element doping. The design and fabrication of MnO2-based composites via the construction of homojunctions and MnO2/ semiconductor/ conductor binary/ ternary heterojunctions are discussed. Their applications in environmental purification systems, either as an adsorbent material for removing heavy metals, dyes, and microwave pollution, or as a thermal catalyst, photocatalyst, and electrocatalyst for the degradation of pollutants are highlighted. Finally, research gaps, challenges, and possible future research in nanostructured MnO2-based materials in environmental applications are presented. Reference: Yang, R., Fan, Y., Ye, R.Q., Tang, Y., Cao, X., Yin, Z., & Zeng, Z. (2021). MnO2-based materials for environmental applications. Advanced Materials, 33(9), 2004862.

Involved Member: Prof. Wenxiong WANG TVP-A, a positively charged photosensitizer with aggregation induced emission characteristics is introduced as a super-efficient, cost-effective, and eco-friendly agent for controlling harmful algal blooms. Due to its positive surface charge, TVP-A has good water solubility and quickly adsorbs onto algal cells floating on the surface of water, triggering algal cell death through oxidative de-struction of the nuclei and chloroplasts of algae. TVP-A is effective at low concentrations and requires sunlight irradiation only for a few minutes to destroy algal blooms, making it applicable for largescale algal bloom control under most weather conditions. The slow self-degradation of TVP-A prevents itsaccumulation and secondary pollution to the environment. Reference: Yue, Q., He, X., Yan, N., Tian, S., Liu, C., Wang, W.X., Luo, L. & Tang, B.Z. (2021). Photodynamic control of harmful algal blooms by an ultra-efficient and degradable AIEgen-based photosensitizer. Chemical Engineering Journal, 417, 127890.

Involved Member: Prof. Wenxiong WANG A novel biosensor for detecting zinc (Zn) in ocean was established, based on the autofluorescence intensity of an adenine deficient yeast (Ade(-) yeast). This biosensor could detect Zn at ultralow concentration (0.01 μM) and accurately quantify the extracellular concentration of Zn ranging from 0.01 to 0.5μM. High tolerance of Ade(-) yeast to salinity, pH variation and other metals enabled its application in complex marine environments. Determining dissolved Zn2+ from a viscous sample, Ade(-) yeast accurately quantified the labile Zn2+ with a lower quantification limit than the chemosensor and higher simplicity than the conventional method. Reference: Sun, A., & Wang, W.X. (2021). Adenine deficient yeast: a fluorescent biosensor for the detection of labile Zn (II) in aqueous solution. Biosensors and Bioelectronics, 179, 113075.  

Involved Member: Prof. Xiaoyan LI Ammonium (NH4+) in wastewater is both a major pollutant and a valuable resource. Flow-electrode capacitive deionization (FCDI) is a promising technology for chemical-free and environmentally friendly NH4+ removal and recovery from wastewater. However, the coexisting sodium (Na+) in wastewater, with a similar hydrated radius to NH4+, competes for the adsorption sites, resulting in low NH4+ removal efficiency. Here, potassium dititanate (K2Ti2O5 or KTO) particles prepared by the electrospray method followed by calcination were mixed with activated carbon (AC) powder to form a novel KTO-AC flow-electrode for selective NH4+ removal over Na+. The mixed KTO-AC electrode exhibits a much higher specific gravimetric capacitance in NH4Cl solution than in NaCl solution. Compared with the pure AC electrode in the FCDI tests on NH4+ removal from synthetic wastewater, 25 wt % KTO addition in the electrode mixture increases the adsorption selectivity from 2.3 to 31 toward NH4+ over Na+, improves the NH4+ removal from 28.5% to 64.8% and increases the NH4+ desorption efficiency from 35.6% to over 80%, achieving selective NH4+ recovery and effective electrode regeneration. Based on DFT calculations, NH4+ adsorption on the K2Ti2O5 (0 0 1) surface is more thermodynamically favorable than that of Na+, which contributes to the high NH4+ adsorption selectivity observed.   Reference: