3D-hydrogels have broad potential for wastewater treatment, for they are separation-free and have excellent adsorption capacity. However, the process of adsorption is only the enrichment of pollutants rather than elimination. Development of 3D-hydrogel/photocatalyst composite materials is a promising strategy for achieving the enrichment and mineralization of organic pollutants. This paper describes a facile and environmentally friendly synthesis of separation-free polyacrylamide/bentonite/graphitic carbon nitride 3D-hydrogel. When the mass of graphitic carbon nitride is 1/10 of acrylamide, the composite hydrogel displays excellent removal of tetracycline in both static and flowing state. The total removal efficiency is higher than that of adsorption or degradation. The enhanced removal of organic pollutants is attributed to the synergistic effect of adsorption and photocatalytic degradation, the enhanced light absorption and the accelerated separation of photogenerated charge carriers. More importantly, it has excellent stability and can be easily separated from water and reused. This 3D-hydrogel/photocatalyst composite materials has broad application potential to the elimination of organic pollutants in water.