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With the rapidly increased discharges of various complex dyeing wastewaters, adsorbents are required to own more properties such as cost-effectiveness, amphoteric ability, and rapid solid-liquid separation ability, to treat dyeing wastewaters. A multi-functional adsorbent was synthesized by co-grafting m-phenylenediamine and sodium allyl sulfonate on the surface of a low-cost base-material: hollow glass microsphere (HGM). Characterization results indicated the surface roughness and –Si–OH groups of HGM were increased by NaOH corrosion; functional groups such as aromatic-rings, –NH 2 , and –HSO 3 − were grafted on the surface of HGM. The synthesized adsorbent showed amphoteric attraction abilities for anionic acid green 25 and cationic basic fuchsin dyes. Kinetics and isotherms studies suggested the PSO model and Langmuir model were most satisfactory for adsorption processes, the theoretical maximum adsorption capacities for acid green 25 and basic fuchsin reached 454.55 and 588.24 mg g−1, respectively. The mechanism investigations indicated the electrostatic attraction, π-π stacking, and hydrogen bonds were the potential interaction forces between dyes and adsorbents. The synthesized material owns self-floating ability due to the hollow structure of HGM, over 95.7% of adsorbents were collected at water surface via the self-floating process in 12 min, which was beneficial to the solid-liquid separation process and the reuse of adsorbents. The technologies developed by these research efforts can serve as templates for synthesizing multi-functional adsorbents for complex wastewaters decontaminations. [Display omitted] • First demonstration of an amphoteric self-floating adsorbent. • The adsorption capacities of anionic/cationic dyes reached 454.55/588.24 mg g−1. • Electrostatic force, π-π stacking, hydrogen bond were dominant adsorption mechanisms. • Over 95.7% of adsorbents were collected at the water surface within 12 min. • The multi-functional adsorbent is beneficial for cleaner production of dyeing goods. [ABSTRACT FROM AUTHOR]