Arsenic compounds are classified as Class I carcinogens due to their high toxicity to the organism. Also, they are easily accumulated in water bodies, and both H2AsO4 and HAsO42− are present simultaneously and convert to each other in a wide pH range. Based on the strategy of simultaneous removal of protons to immobilize AsO43−, a monodispersed porous pinecone-like Mg(OH)2 (PLMH) was prepared via a facile and environmentally friendly ultrasound-assisted precipitation route for deep As(V) removal. The PLMH presents a porous and stable framework structure formed by crossed lamellae, and the As(V) solution can be completely immersed inside, which gives a ‘surface effect’ inside the microsphere and makes the As(V) capture performance much higher than the general adsorbents by the removal of protons to immobilize AsO43−. In addition, the PLMH has an extremely wide pH applicability range (pH 3–12), special pH effects, and symmetry phenomena. These performances indicate that the PLMH can be a good candidate for the treatment of real arsenic industrial wastewater.

  • The PLMH exhibits exaggerated adsorption properties for water contaminated with As (945.8 mg·g−1).

  • The first discovery of interesting pH symmetry of the PLMH in wastewater contaminated with As.

  • The PLMH can be mass-produced and has great prospects for real wastewater applications.

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