Adsorption is a commonly used technique for removing contaminants from wastewater, such as hexavalent chromium (Cr(VI)) from the wastewater of a chrome plating plant. Chitosan, a prevalent polymeric biomass that is used industrially as a wastewater treatment adsorbent, was crosslinked and functionalized with a low-cost phosphonium salt to enhance its adsorption capacity for Cr(VI). At Cr(VI) concentrations below 130 ppm, the phosphonium-crosslinked chitosan (PCC) adsorbed more than double the amount of Cr(VI) than the unmodified chitosan. The low-cost method for manufacturing PCC may provide a cost-effective alternative to simply increasing the amount of chitosan used in a process. Additionally, PCC was regenerated using magnesium sulfate for repeated use. The recovered Cr(VI) may be recycled back into a chrome plating process.