Synthesis of Porous Materials Using Magnesium Slag and Their Adsorption Performance for Lead Ions in Aqueous Solution.

Magnesium slag-based porous materials (MSBPM) were successfully synthesized using alkali activation and foaming methods as an effective adsorbent for Pb2+ in solution. The effects of foaming agent type, foaming agent dosage, alkali dosage, and water glass modulus on the properties of the MSBPM were studied, and the micromorphology and porosity of the MSBPM were observed using microscopy. The influence of pH value, initial concentration, and adsorbent dosage on the Pb2+ adsorption was investigated. The results showed that a porous material (MSBPM-H2O2) with high compressive strength (8.46 MPa) and excellent Pb2+ adsorption capacity (396.11 mg·g-1) was obtained under the optimal conditions: a H2O2 dosage of 3%, an alkali dosage of 9%, a water glass modulus of 1.3, and a liquid-solid ratio of 0.5. Another porous material (MSBPM-Al) with a compressive strength of 5.27 MPa and the Pb2+ adsorption capacity of 424.89 mg·g-1 was obtained under the optimal conditions: an aluminum powder dosage of 1.5‱, an alkali dosage of 8%, a water glass modulus of 1.0, and a liquid-solid ratio of 0.5. When the pH of the aqueous solution is 6 and the initial Pb2+ concentrations are 200~500 mg·L-1, the MSBPM-H2O2 and MSBPM-Al can remove more than 99% of Pb2+ in the solution. The adsorption process of both materials followed the Langmuir isotherm model and pseudo-second-order kinetic model, indicating that the adsorption process was a single-molecule layer chemical adsorption.

Modification of waste coal gangue and its application in the removal of Mn(2+) from aqueous solution.

We developed a new calcination method to convert coal gangue (CG), a common waste generated from coal production process, into a modified form, which could be used as an adsorbent to remove Mn(2+) from aqueous solution. Sodium tetraborate (Na2B4O7·10H2O) was added into the CG calcination process as an additive, and the concentrations of Na2B4O7·10H2O were optimized along with the calcination temperature to obtain the best adsorbent capacity of modified coal gangue (MCG). We applied multiple analytical methods such as scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analysis to characterize the MCG. The results showed it had a smaller particle size and a larger specific surface area and pore volume after modification. It also indicated that the phase of CG transformed from kaolinite to metakaolinite after calcination. Moreover, a new substance was generated with two new peaks at 1,632 cm(-1) and 799 cm(-1). The Mn(2+) absorption capacity of MCG was evaluated using a series of experiments with different adsorbent doses, pH values and initial Mn(2+) concentrations during the adsorption process. We found that Mn(2+) adsorbent capacity of MCG increased by more than seven-fold compared to that of CG. The Langmuir isotherm model and the pseudo-second-order kinetic model provided the best fit to the adsorption processes.