Silver, with excellent physicochemical properties, has been widely used in modern industry. Silver recovery from end-of-life product is economically significant for sustainability. However, silver leaching solution (SLS) containing diverse heavy metal ions as well as dissolved silica is a challenging waste stream for treatment and silver recovery. In this work we explored treatment of a real SLS via direct contact membrane distillation (DCMD). Results showed that silica scaling in DCMD process was closely related to the coexisting aluminum ions (Al3+) in SLS. The amount of Al(OH)3 formed was dependent on the initial pH of SLS and was effective to reduce concentration of the total dissolved silica in SLS, which was the key factor that influenced particle size distribution of SLS and degree of silica scaling. The highest silica removal rate of 83.7% was achieved at pH of 11. Moreover, it was found that the Al(OH)3 with positive charge accelerated mono-silicic acids aggregation, leading to prompt silica polymerization. This hypothesis was underpinned by evidence that amorphous yet compact aggregates formed on membrane surface and trimer silicates formed in the concentrated SLS with initial pH of 11. As a result, the most severe silica scaling occurred during DCMD treatment of SLS, resulting in the lowest initial permeate flux and water recovery. Our results shed light on prevention and management of silica scaling in treatment of waste stream.