Biomass porous carbons derived from Laminaria japonica were prepared by KOH and H3PO4 activation methods, respectively. The results indicated that the chemical activation had an apparent effect on the molecular framework and space of materials. To enhance the selective adsorption for organic acids, biomass carbons were modified by dopamine combined with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane. The SEM and BET results illustrated the effect of the chemical activation approach on the morphology and porous texture. The biomass porous carbon using KOH activation method had the highest surface area (up to 1558 m2/ g). Compared with unmodified materials, the modified materials showed higher adsorption capacity for organic acids (27.90 μg/mL for chlorogenic acid and 25.47 μg/mL for caffeic acid). It was suggested that modification of porous carbons might be a viable pathway to increase the specific adsorption affinity and efficiency for organic acids in dried jujube samples.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials and reagents
        2.2 Synthesis of biomass porous carbon materials
        2.3 Synthesis of KH-792@PDA-BC composite
        2.4 Static and dynamic adsorption capacity
        2.5 Ultrasound-assisted dispersive solid-phase extraction
        2.6 Characterization of materials
    3 Results and discussion
        3.1 The morphological microstructures of the materials
        3.2 The elemental composition and ionic state of materials
        3.3 Comparison of adsorption performance
        3.4 Method validation of UA-DSPE-HPLC
        3.5 Determination of CGA and CFA in dried jujube
        3.6 Reusability
    4 Conclusions
    Acknowledgements 
    References

• Qi Wang(Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry and Chemical Engineering, Tianjin University of Technology)
• Yaying Lv(Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry and Chemical Engineering, Tianjin University of Technology)
• Tao Zhu(Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry and Chemical Engineering, Tianjin University of Technology)