It soon could become much harder for recycling centers across the U.S. to turn a profit, and some instead could divert reusable materials to landfills, thanks to a looming Chinese import ban on certain types of recycled materials.

China is by far the biggest importer of U.S. recyclables, but part of that market is about to close: The Chinese Ministry of Environmental Protection (MEP) notified the World Trade Organization in July that it would ban imports of certain types of...