There is an increasing emphasis on the transformation of lignocellulosic biomass into versatile products. The feasibility of preparing xylooligosaccharides (XOS) by hydrolysis of sorghum stalk (SS) using organic and inorganic acids was studied. The influences of different acids (gluconic acid, acetic acid, sulfuric acid, and oxalic acid), process time and temperature on the hydrolysis of SS were explored. The findings indicated XOS yield can be maintained at a high level under different conditions with organic acid pretreatments. Optimum yield of XOS (39.4%) was obtained using sulfuric acid (pH 2.2) at 170 °C and 75 min of process time. It is suggested when reaction temperature and time were increased, both X5 and X6 are cracked into XOS with lower molecular mass such as X2, X3, and X4. Moreover, the results based on mass balance showed that up to 110 g (XOS) plus 117 g (glucose) can be recovered from 1000 g of SS. Results will give insights into establishing an efficient acid pretreatment of sorghum stalk to coproduction of XOS and glucose.

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Adsorption capacity, selectivity and adsorption rate are all important indicators to judge the performance of an adsorbent. At present, most of the studies on gold recovery with adsorbents have weakened the consideration of adsorption efficiency. Therefore, there is a need to develop an adsorbent with fast adsorption rate for gold ions to ensure high adsorption capacity and selectivity. Here, we report two humic acid-derived sulfonated resins (SHAR and NSHAR) using sulfuric acid and sodium sulfite as sulfonating agents respectively, which were prepared by a simple two-step method using water as solvent. They can recover Au(III) quickly and efficiently from mixed metals (Fe(III), Mn(Ⅱ), Cu(Ⅱ), Cr(III), Mg(Ⅱ), Ni(Ⅱ), Sn(Ⅱ), Co(Ⅱ), Pb(Ⅱ) and Zn(Ⅱ)). Adsorption behavior and mechanism of Au(III) on SHAR and NSHAR were studied. The Freundlich isotherm model and the Pseudo-second-order kinetic model are suitably for the description of Au(III) behavior meaning that the process belongs to multi-molecular chemical adsorption. Furthermore, adsorption thermodynamic study indicates that the adsorption of Au(III) on SHAR and NSHAR is endothermic and spontaneous. Different from conventional adsorbents, Au(III) are reduced to element gold and deposited on the adsorbent. NSHAR takes only 10 min to reach adsorption equilibrium, and the adsorption capacity is up to 927 mg·g− 1 (SHAR needs 50 min with capacity of 1440 mg·g− 1). This research provides a new scheme and idea for quickly and efficiently recovering gold.

Adsorption capacity, selectivity and adsorption rate are all important indicators to judge the performance of an adsorbent. At present, most of the studies on gold recovery with adsorbents have weakened the consideration of adsorption e ciency. Therefore, there is a need to develop an adsorbent with fast adsorption rate for gold ions to ensure high adsorption capacity and selectivity. Here, we report two humic acid-derived sulfonated resins (SHAR and NSHAR) using sulfuric acid and sodium sul te as sulfonating agents respectively, which were prepared by a simple two-step method using water as solvent. They can recover Au(III) quickly and e ciently from mixed metals (Fe(III), Mn( ), Cu( ), Cr(III), Mg( ), Ni( ), Sn( ), Co( ), Pb( ) and Zn( )). Adsorption behavior and mechanism of Au(III) on SHAR and NSHAR were studied. The Freundlich isotherm model and the Pseudo-second-order kinetic model are suitably for the description of Au(III) behavior meaning that the process belongs to multi-molecular chemical adsorption.Furthermore, adsorption thermodynamic study indicates that the adsorption of Au(III) on SHAR and NSHAR is endothermic and spontaneous. Different from conventional adsorbents, Au(III) are reduced to element gold and deposited on the adsorbent. NSHAR takes only 10 min to reach adsorption equilibrium, and the adsorption capacity is up to 927 mg•g − 1 (SHAR needs 50 min with capacity of 1440 mg•g − 1 ). This research provides a new scheme and idea for quickly and e ciently recovering gold.