## 4 Conclusions  
The nano-bioadsorbent prepared from sweet lime pulp waste (nZVISLP) showed exciting results in MB removal from an aqueous solution. This nano-bioadsorbent was most effective at alkaline pH (10), whereas the acidic conditions were not favorable. The equilibrium values predicted using the DEO-based optimized isotherm parameters were in close agreement with the experimental values. The \(R^{2}\) values were \(>\)0.95 for all studied isotherms, and the \(R^{2}\) values for the Freundlich and Sips isotherm models were \(\sim\)0.98, thus validating that these isotherms best depict MB adsorption onto nZVISLP. The higher \(\chi^{2}\) values (\(\geq\)0.98) also confirmed the suitability of these isotherms. Similarly, the kinetic model parameters evaluated by DEO were able to capture the kinetics of MB adsorption, thus resulting in higher \(R^{2}\) and lower RMSE. The endothermic and spontaneous nature of the adsorptive removal of MB onto nZVISLP was confirmed by the results of the thermodynamic study. The treatment of wastewater and the application of prepared nZVISLP may reduce pollution loads in surface water. The prepared iron particles are highly active for the adsorptive treatment of MB-contaminated water.  
**Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/9/23/5112/s1](http://www.mdpi.com/2076-3417/9/23/5112/s1)]([http://www.mdpi.com/2076-3417/9/23/5112/s1](http://www.mdpi.com/2076-3417/9/23/5112/s1)): Table S1. Various forms of isotherm models for single component expressed in linear and non-linear forms. Table S2. Summary of different conventional type of kinetics both in linear and non-linear forms generally used to estimate the adsorption rate along with corresponding plot to estimate the parameters. Table S3. Pseudo first order and second order kinetics for the removal of MB by nZVISLP. Table S4: Thermodynamic parameters of MB adsorption onto the nZVISLP. Figure S1. pHzpc of synthesized SLP-IPs. Figure S2. (a) Pressure variation on adsorption/desorption of N2 (b) variation in dVP/drp (c) BET plot. Figure S3. XRD pattern of prepared nZVISLP to identify crystallinity of particles and confirmation of zero valent iron. Figure S4. The pseudo 1 st order and pseudo 2 nd order kinetics study for the adsorption of MB onto nZVISLP at different initial dye concentrations (C0 = 10, 20, 30 and 40 mg/L; T = 293 K; adsorbent concentration=1.2g/L; initial pH 8.0). Figure S5. Intraparticle diffusion model for the adsorption of MB on to nZVISLP with different initial dye concentrations (C0 = 10, 20, 30 and 40 mg/L; T = 293 K; adsorbent concentration=1.2g/L; initial pH 8.0). Figure S6: Plots of lnKC versus 1/T of the adsorption of MB onto the nZVISLP.  
**Author Contributions:** Conceptualization, J.R.K. and J.S.; methodology, J.S., N.S., and S.R.; software, R.R.K.; validation, R.R.K., J.R.K., and J.S.; formal analysis and investigation, N.S., J.-S.C., S.L., and S.R.; data curation, N.S. and J.-S.C.; writing--original draft preparation, N.S. and S.R.; writing--review and editing, J.R.K., J.S., and R.R.K.; visualization, J.-S.C. and S.L.; supervision, J.S.; project administration, J.S.  
**Funding:** This research was funded by the University Grant Commission (Grant No. F. 30-382/2017, BSR (UGC-BSR Research start-up grant), and the Science and Engineering Research Board (SERB), Department of Science and Technology (Grant No. ECR/2016/001924), Government of India. In addition, financial support was obtained from a Kwangwoon University Research Grant 2019, Seoul, Korea.  
**Acknowledgments:** The authors are grateful to the University Grant Commission (Grant No. F. 30-382/2017, BSR (UGC-BSR Research startup grant), and the Science and Engineering Research Board (SERB), Department of Science and Technology (Grant No. ECR/2016/001924), Government of India for the financial support of this research, as well as the Kwangwoon University Research Grant 2019, Seoul, Korea.  
**Conflicts of Interest:** The authors declare no conflicts of interest.