Novel eco-friendly adsorbents were prepared through pyrolysis and acid activation of raw almond leaf (RAL) to form almond leaf biochar (ALB) and chemically activated almond leaf biochar (CAL), respectively. The prepared adsorbents were characterized using TGA, FTIR, SEM–EDX, BET and XRD techniques and their physicochemical properties investigated. RAL, ALB and CAL were utilized for adsorption of BPB dye from aqueous solution using batch technique under optimum conditions. The optimum dye adsorbed by RAL, ALB and CAL were 92.83, 93.21 and 94.89%, respectively at pH 3, dye initial conc. (100 mg/L), adsorbent dose (0.04 g/25 mL), 60 min contact time and 301 K adsorption temperature. Although, Langmuir maximum monolayer adsorption capacities were found to be 365.36, 535.62 and 730.46 mg/g for RAL, ALB and CAL, respectively, but isotherm conformed to Freundlich model. Kinetic study confirmed suitability of pseudo-second-order model with rate constant 9.33 × 10–4, 9.91 × 10–4 and 12.60 × 10−4 g mg−1 min−1 for RAL, ALB and CAL, respectively. Negative values of thermodynamic parameters (ΔG and ΔH) established sequestration process to be spontaneous and exothermic. RAL, ALB and CAL were discovered to be highly efficient adsorbents that could be used in place of expensive commercial adsorbents.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Preparation of adsorbents
        2.3 Characterization of adsorbents
    3 Results and discussion
        3.1 Physicochemical and thermal analysis of the adsorbents
        3.2 Fourier transform infrared spectrometry
        3.3 Scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDX)
        3.4 N2 adsorption–desorption isotherms
        3.5 XRD analysis of RAL, ALB and CAL
        3.6 Zero potential charges (pHpzc)
        3.7 BPB dye adsorption mechanism onto prepared adsorbents
        3.8 Adsorption experiments
        3.9 Adsorption models
    4 Conclusion
    Acknowledgements 
    References

• Jamiu Mosebolatan Jabar(Textile and Polymer Research Laboratory, Chemistry Department, The Federal University of Technology)
• Ignatius Adekunle Owokotomo(Textile and Polymer Research Laboratory, Chemistry Department, The Federal University of Technology)
• Yusuf Timilehin Ayinde(Textile and Polymer Research Laboratory, Chemistry Department, The Federal University of Technology)
• Ayodele Modupe Alafabusuyi(Textile and Polymer Research Laboratory, Chemistry Department, The Federal University of Technology)
• Gbolahan Olusayo Olagunju(Textile and Polymer Research Laboratory, Chemistry Department, The Federal University of Technology)
• Victor Oluwafemi Mobolaji(Textile and Polymer Research Laboratory, Chemistry Department, The Federal University of Technology)