Preventing release of refractory pollutants from contaminated sediments is of growing concern. In situ remediation of sediments becomes more popular because of its low cost and noninterference of benthic ecosystems compared with conventional sediment dredging. In this study, a low-cost rice husk biochar (RHB) was used as a capping material to prevent the release of representative inorganic (Cu2+) and organic (4-chlorophenol, 4-CP) pollutants from synthetic contaminated sediments. In addition, the release dynamics of pollutants was investigated under different environmentally relevant conditions. The experimental results indicated that RHB can efficiently suppress the release of Cu2+ and 4-chlorophenol from the sediments and a select thickness of RHB can maintain the concentrations of these model pollutants below the national criterion at pH = 5 and 7, even when the concentrations of these pollutants are very high (1600 mg kg(-1) of Cu2+ or 100 mg kg(-1) of 4-CP). Fitting the release data of pollutants to the zero order equation, the Elovich equation, the parabolic diffusion law, and the two-constant rate equation demonstrated that a simple model cannot precisely describe the complicated release kinetic process of the pollutants. This study demonstrated a facile remediation application of RHB and helped to provide the information needed for future risk assessments and policy-making.