Chemical modification of Pinus walliichiana sawdust: Application in membrane system for efficient purification of groundwater containing Cd(II) and Ni(II)

In the Sargodha region of Pakistan, the concentrations of Cd(II) and Ni(II) ions are very high as compared to WHO and US EPA standards and may be one of the leading reasons for water-borne diseases in the population of this area. In the current research work, an eco-friendly, low-cost, effective, and reusable filter membrane system is developed. The cellulose sawdust of Pinus walliichiana (PWC) was treated with succinic anhydride to form Pinus walliichiana cellulose succinate (PWCS) and finally converted to sodic form (PWCS-Na) by treating with saturated sodium bicarbonate. The PWCS and PWCS-Na as obtained were characterized using FTIR, pH_ZPC, SEM, PXRD, and Brunauer–Emmett–Teller (BET) analysis. The BET surface area of the PWCS-Na was found to be 579.5 m²/g. Maximum sorption capacity values in the batch study for Cd(II) (235.2 ± 10.3 mg g⁻¹) and Ni(II) (195.6 ± 15.2 mg g⁻¹) were observed at 298 K, pH 6, sorbent dosage of 30 mg, and metal ion concentration of 70 mg/L. The filter membrane system was designed and employed for the purification of the flowing water system. Theoretical calculations show that 1 L of filter membrane containing 138.0 g of the adsorbent PWCS-Na can purify 532.8 L solution with Cd(II) concentration 70 mg/L and 278.2 L solution of Ni(II) with concentration 70 mg/L. The regeneration study proved the efficient reusability of sorbent after five cycles with a slight change in sorption capacity.