| With the rapid development of industry, the water pollution has become the serious problem to human, especially the heavy metal pollution is extremely harmful to the health of people, thus, it is significant to remove the water pollution through developing the effective adsorbent. Here, for the Cr(VI) removal as sample, using sodium alginate and iron salt as the precursor to fabricate two different macro structure adsorbents through the heating treatment and the batch experiments show that the as-received adsorbents have achieved better performance. With comparison the two different preparation methods, it is seen that the MMCB which was prepared by the second method has the much broader application prospect. At the inert atmosphere, the sodium alginate would become bio-carbon by the heating treatment. The ferric salt would become magnetic nano-material by the carbon thermal reduction. Combination with the above two kind of properties, the sodium alginate is cross-linked by Fe3+ ions to fabricate the magnetic carbonaceous adsorbents which have the high porosity and special chemical properties and the adsorbent can be applied to the effective removal of heavy metal pollution from the aqueous system.In the section one, we have prepared the adsorbent of Fe-SA-X and study the effect of different carbonization temperature to the performance of adsorbent. The results show that Fe-SA-800 is better than Fe-SA-400 and Fe-SA-600 and indicate that the higher temperature, the better performance. The experimental parameters were investigated in detail, the optimum pH was 2.0; the adsorption kinetics was better fitted the pseudo-second order, the adsorption isotherm was better fitted the Langmuir isotherm model and indicated that the adsorption was monolayer adsorption. The 0<RL<1 showed that the adsorption was favorable. The adsorption process was not influenced by the temperature. The investigation about the strength of common ions showed that the adsorption mechanism maybe competition and the adsorption capacity was influenced much greatly by the ion which has more negative charges. The reusability test proved that the adsorbent could be reused three cycles and its removal efficiency maintain 80% of the fresh material, the result showed that the adsorbent can be reused and has good stability. At last, the possible mechanism was discussed in detail with the aid of FTIR and XPS technologies. The adsorption process involved the electrostatic attraction and redox reaction and the formed Cr(III) was retained in the pores of adsorbent.Based on the first study, we have introduced the ion-exchange mechanism in the second work. Since the mechanical stability of hydrogel beads which was prepared by Ca2+ was much greater than Fe3+, so we have fabricated the monolithic magnetic carbonaceous beads(MMCB) which have much higher porosity and its adsorption capacity increased from 86.32 to 143.20mg/g. The experimental parameters were studied in detail and the received data was better fitted pseudo-second kinetic model and Langmuir isothermal model. In the thermal investigation, since of ΔH>0, ΔS>0, and ΔG<0, we can concluded that the Cr(VI) adsorption was spontaneous and endothermic. The adsorption mechanism and reusability test were also discussed. Most importantly, with comparison the Fe-SA-X, the MMCB has better mechanical strength and easier operation, therefore the MMCB can be applied in the heavy metal ion removal from the practical industry waste water. |
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