BEIJING — A former journalist who became the public face of a campaign seeking justice for children harmed by tainted dairy products was sentenced Wednesday to two and a half years in prison on charges that his efforts disrupted social harmony.

Zhao Lianhai, whose own son was sickened in 2008 by baby formula laced with the industrial chemical melamine, had been accused of “inciting social disorder” for speaking to foreign reporters, publicly displaying magazine-size protest signs and organizing aggrieved parents through a Web site. His lawyer, Peng Jian, said he would appeal the sentence, which was issued by a court in suburban Beijing