Fabrication of In-S-co-doped two-dimensional BiOCl coupling with surface hydroxylation toward simultaneously efficient charge separation and redox capability for photocatalytic water remediation.

Tailoring energy band structure of bismuth oxychloride (BiOCl)-based photocatalysts by virtue of the metal and/or non-metal elements is one of the promising strategy to address environmental issues, especially plays a crucial role in water remediation. However, it still remains a great challenge to balance the light-harvesting and charge carriers separation. Herein, a feasible strategy was proposed for the simultaneous integration of energy-band modulation and surface hydroxylation to alleviate the as-mentioned contradiction and long-standing issues. By using a simple one-pot hydrothermal method, In-S-co-doped BiOCl photocatalyst coupling with surface hydroxylation (denoted as In/BOC-S-OH) was prepared by the simultaneous co-precipitation and ripening process and exhibited a good photocatalytic activity for removing tetracycline (TC) under visible light-irradiation than the counterparts of In-doped BiOCl (In/BOC), S-doped BiOCl (In/BOC-S) or surface -OH modification BiOCl (In/BOC-OH). Such satisfied photocatalytic efficiency benefits from the synergistic effect on the visible light capture, charge migration and separation associated with the introduction of intermediate energy levels and surface defect, respectively. Accompanying with the introduction of In and S hetero-atoms intercalation, both the potentials of valence and conduction bands were adjusted and the reduction of the bandgap could promote the capture of photons. Meanwhile, the powerful polarization effect associated with the non-uniform charge distribution could promote the special separation of carriers. More importantly, the surface defects induced by hydroxylation could act as traps for photogenerated electrons to stimulate the rapid separation of carriers, thereby causing the cleavage of antibiotics on the catalytic surface. This research offers a reliable strategy and promising scheme via effective solar energy conversion and charge carrier separation to advance photocatalytic wastewater remediation.

Selective removal behavior and mechanism of trace Hg(II) using modified corn husk leaves.

Removal of Hg(II) from wastewater was beneficial to satisfy the discharge standards of China's mercury-containing wastewater (50 ppb). An adsorbent was prepared via modifying corn husk leaves with bismuthiol I. The results revealed that the mercury removal rate was more than 98.5% at pH 1.0-7.0. Moreover, the removal rate reached 96% at 5 min and the residual concentration decreased from 10 ppm to approximately 30 ppb. In addition, the adsorbent owned a conspicuous selective absorbability for trace Hg(II) from wastewater. The adsorption process followed a Hill isotherm model. The actual saturated adsorption quantity of the adsorbent was 707 mg/g. The repeatability experiment indicated that the mercury removal efficiency was still beyond 99% after three cycles. The X-ray photoelectron spectroscopy suggested that the main adsorption mechanism was chelation between nitrogen/sulfur groups and Hg(II). The adsorbent was hopeful to remove mercury from wastewater in a sustainability perspective.