Phenylboronic Acid Functionalized Adsorbents for Selective and Reversible Adsorption of Lactulose from Syrup Mixtures

Boronate affinity materials have been widely used for enrichment of cis-diol molecules. In this work, phenylboronic acid functionalized adsorbents were prepared via a simple and efficient procedure grafting phenylboronic acid groups onto amino macroporous resins. Elemental analysis has confirmed the successful functionalization of AR-1M and AR-2M with approximately 2.17% and 0.73% weight percentage of boron. Comparatively, AR-1M possessed higher lactulose adsorption capacity (q_e‑Lu, 84.78 ± 0.95 mg/g dry resin) under neutral conditions (pH = 7), while the introduced glutaraldehyde spacer arms on AR-2M resulted in excellent adsorption selectivity (α ≈ 23), high adsorption efficiency (π ≈ 22%), and fast adsorption/desorption rate. The purity of lactulose (Pu_D^Lu) through pH-driven adsorption (pH 7–8) and desorption (pH 1.5) can be effectively improved depending on the ratio of lactulose to lactose. When lactulose/lactose ≥ 1:1, Pu_D^Lu ≈ 95% was achieved. No significant drop in q_e‑Lu (>90%) was observed after ten-consecutive repeats. Results demonstrated that the newly developed method may achieve satisfactory performance in lactulose purification.