# Biosorption of Pb(II) Using Coffee Pulp as a Sustainable Alternative for Wastewater Treatment
## 3 Results and Discussion
### Kinetics and Adsorption Isotherm
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Lignocellulosic**} & \multicolumn{4}{c}{**Biosorption Characteristics**} \\ \cline{2-5}  & **pH** & **Capacity of Maximum Adsorption (Q max.)** & **Q max. Interval** & **Reference** \\ \cline{2-5}  & **Offee Crops** & **(pH Units)** & **(mg:g\({}^{-1}\))** & **(mg:g\({}^{-1}\))** & **(47)** \\ \hline \hline \multirow{5}{*}{Coffee waste (instant coffee beans)} & 5.0 & 9.70 & 9.70 & [47] \\ \cline{2-5}  & 5.0 & 54.05 & & [48] \\ \cline{2-5}  & N/A & 37.04 & & [49] \\ \cline{2-5}  & 4.5 & 4.80 & & [50] \\ \cline{2-5}  & 0.5–9.0 & 7.20 & 4.80–230.00 & & [31] \\ \cline{2-5}  & 0.5–9.0 & 230.00 & & & \\ \cline{2-5}  & 2.0–9.0 & 50.80 & & & \\ \cline{2-5}  & 2.0 & 24.10 & & & This study \\ \hline \multirow{5}{*}{Raw coffee beans} & 6.0 & 61.60 & & [51] \\ \cline{2-5}  & 5.0 & 22.90 & 22.90–61.60 & [52] \\ \cline{2-5}  & 3.0–4.0 & 96\% & & [50] \\ \cline{2-5}  & N/A & 87.20 & & [53] \\ \cline{2-5}  & 3.0–4.0 & 87.02 & 87.02–159.54 & & \\ \cline{2-5}  & 2.0–12.0 & 93.24 & & [50] \\ \cline{2-5}  & 2.0–12.0 & 159.54 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._  
Figure 4: Adsorption isotherm for Pb(II) with CP. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Lignocellulosic Waste**} & \multicolumn{4}{c}{**Biosorption Characteristics**} \\ \cline{2-5}  & **pH** & **Q max.** & **Chemical Modification** & **Reference** \\ \cline{2-5}  & **(pH units)** & **(mg:g\({}^{-1}\))** & **(m:g\({}^{-1}\))** & **(45)** \\ \hline \hline \multirow{2}{*}{Spent coffee powder/coffee grounds} & 3.5 & 159.50 & Citric acid & [45] \\ \cline{2-5}  & 4.0 & 158.70 & Citric acid & [46] \\ \hline \hline \multirow{2}{*}{Coffee shell/pulp} & 5.0 & 54.05 & Pyrolysis & [48] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Capacity of maximum adsorption of coffee wastes with chemical modification. Table 4 presents the capacities of maximum adsorption of coffee wastes without chemical modification, while Table 5 reports this parameter but with chemical modification, where citric acid and pyrolysis methods were used. For each one, an interval was proposed which was carried out taking into account the lower value with respect to the upper value of those reported by the cited references for the same waste, and it was found that the value of the present research, in relation to the coffee beans, was below the exposed range, unlike raw coffee beans and coffee husk/pulp, that were in the range of unmodified residues. Similarly, when carrying out the same comparative analysis, but with chemically modified coffee residues, the value presented in this study was below the minimum value of the range. It should be added that the objective of carrying out a chemical modification of a sorbent is performed in order to increase the active sites (functional groups) on its surface and thus augment the removal of the contaminant in the aqueous solution and its capacity of maximum adsorption. Additionally, [PERSON] et al. [4] presented some non-conventional technologies used for the removal of Pb\({}^{2+}\) in aqueous matrices in the years 2010-2019, among which the use of biopolymers, bio-remediation techniques (algae, fungi, yeasts and bacteria) and agro-industrial wastes were highlighted. Within the aforementioned techniques, the percentage of efficiency ranged between 80% and 100% for the removal of this metal ion, with the exception that agricultural wastes showed a higher efficiency compared to the others, including guava seeds and melon peels with maximum adsorption capacities of approximately 96 mg\(\cdot\)g\({}^{-1}\).