Membrane separation technologies are extensively applied for ionic contaminant treatment, but the specific interaction means between composite membranes and contaminants are mostly unnoticed. Herein, hierarchically structured La(OH)3@MoS2@Cellulose-Lignin (La(OH)3@MoS2@CL) composite membranes were fabricated through hydrothermal and co-blending methods for tellurium separation. The obtained La(OH)3@MoS2@CL composite membrane effectively achieved a rejection rate of 98.61% under acidic conditions, facilitating the treatment and practical application to acidic tellurium-containing wastewater. Meanwhile, the relatively small contact angle and hydrophilic properties make it exhibit superior antifouling properties, which contribute to its application in complex environments. Besides, La(OH)3@MoS2@CL also exhibits excellent stability and regeneration properties, which are beneficial to prolong the service life of the composite membrane. Importantly, results reveal that composite membranes achieve tellurium separation of contaminants through reduction and ion exchange, which further reinforces the interaction forces of the composite membrane with ionic contaminants. Therefore, this work illustrates the mechanism of action for separating ionic contaminants and provides a channel for decontaminating similar contaminants in water treatment and environmental remediation.