Algaecide for flocculating and settling alga bodies and preparation method of algaecide

The invention relates to an algaecide and a preparation method thereof. The algaecide for flocculating and settling alga bodies contains the following components in parts by weight: 1000 parts of sodium alginate and 100-900 parts of multi-walled carbon nanotubes, wherein sodium alginate is added into deionized water at first, then the mixture is subjected to magnetic stirring until the sodium alginate is completely dissolved, and then 0.8-2.4 parts of the multi-walled carbon nanotubes or/and gallic acid are added. According to the preparation method of the algaecide, the sodium alginate, the multi-walled carbon nanotubes and an allelopathic substance namely the gallic acid are used as main ingredients to prepare a composite hydrogel ball algaecide, and the preparation method comprises the following steps: (1) adding a certain amount of sodium alginate/gallic acid into the deionized water, and performing magnetic stirring until the sodium alginate/gallic acid is completely dissolved; (2) adding the multi-walled carbon nanotubes, and mixing uniformly by using an ultrasonic assisted oscillation method to prepare a dispersion; (3) dropwise adding the dispersion into a 5-10% CaCl2 solution by using a dropper to cure into calcium gel balls, fixing for about 1-2h, then taking out, then flushing repeatedly with deionized water, and standing to remove surface residues; and (4) performing vacuum drying to prepare the algaecide.