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This study focused on the investigation microplastics (MPs) with a size of ≤1.0 mm in sand samples from Thanh Phu beach, Ben Tre, Vietnam. MPs in sand from the clam beach (from 39.67 ± 6.67 to 92.00 ± 12.93 items kg-1 dried sand) were higher than those from the bathing beach (from 21.33 ± 8.76 to 51.67 ± 16.11 items kg-1 dried sand), indicating a direct contribution of MPs from coastal aquaculture. For the clam beach, MPs in surface samples (0-4 cm) were lower than in deep samples (4-6 cm). In contrast, MPs in surface samples (0-2 cm) from the bathing beach were higher than deep samples (2-5 cm). A combination of microscopy and Fourier-transform infrared spectroscopy methods confirmed that 62.5% of the representative MPs samples or 18.9% of the suspected MPs samples were plastics. Low-density polyethylene, polypropylene and polyethylene terephthalate were the largest in abundance. Further studies are needed to assess the environmental risk of MPs accumulation.

A superior heterojunction of HC-ZnBi-LDO was synthesized in two steps, namely hydrothermal carbonization, followed by co-precipitation. The 2% HC-ZnBi-LDO heterojunction photocatalysts could degrade over 90.8% of 30 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) using 1.0 g/L of the catalyst after 135 min of visible light exposure at pH 4. The activity of 2% HC-ZnO-LDO was remarkably stable. Approximately 86.4-90.8% of 30 mg/L 2,4-D was degraded, and more than 79-86.4% of TOC was mineralized by 2% HC-ZnBi-LDO at pH 4 after 135 min of visible light exposure during four consecutive cycles. The rapid separation and migration of charge carriers at the interfaces between HC and ZnBi-LDO were achieved within 2% HC-ZnBi-LDO. Moreover, the electron acceptor characteristic of HC in 2% HC-ZnBi-LDO caused the recombination of charge carriers to decrease significantly, thus generating more reactive radicals, such as hydroxyl radicals (OH ● ) and superoxide radicals (O 2 ●- ). These results demonstrate that the novel 2% HC-ZnBi-LDO is a superior photocatalyst for the remediation of hazardous organic pollutants.