## 3 Results and Discussion
### Adsorption Capacity of Bioadsorbents  
In the experimentation carried out to evaluate the adsorption capacity of Cd\({}^{2+}\) ions using the biosorbents prepared OPB, CCR, YP, CP and CH, the effect of temperature, particle size and adsorbent dose in the process was studied. The adsorption capacity of the metal was calculated using Equation (2). As summarized in Table 2, the highest absorption capacity of Cd\({}^{2+}\) is obtained for all the biosorbents YP, OPB, CH, CP, CCR, at the conditions of temperature 55 \({}^{\circ}\)C, particle size 0.5 mm and dose of 0.03 g adsorbent, obtaining values of 123.66, 197.95, 160.83, 76.86, 105.40, mg/g respectively. It can also be observed that the process is endothermic, because the behavior of the Cd \({}^{2+}\) adsorption capacity of all the biomaterials studied shows that an increase in temperature favors removal, in the range of 40 \({}^{\circ}\)C to 80 \({}^{\circ}\)C. The increase in the removal efficiency of Cd\({}^{2+}\) due to the increase of this parameter could be due to the union between the adsorbent and adsorbent by the formation of new active sites, these sites could form new bonds between ions and the active functional groups in the adsorbent, overcoming the activation energy barrier and improving the intraparticle diffusion rate bonding [5; 53; 54]. The reduction in adsorption capacities at temperature of 70 \({}^{\circ}\)C for the CH, CP y CCR is attributed to the tendency of the process to desorb when adding higher heat not needed, more cadmium ions escape from the solid phase [53; 55]; from elsewhere, YO y OPB show that the adsorption capacity increases as a function of temperature at the different conditions of particle size and dose of adsorbent evaluated. It is observed that the adsorption capacity behaves inversely proportional to the increase in particle size of YP and OPB, which may be due to the fact that a decrease in particle size the surface area is larger due to the number of pores, thus increasing the active junction sites and the available contact surface, resulting in a higher mass transfer and faster adsorption [56; 57]. On the other hand, when using CCR, CH and CP, it was found that 0.5 mm particle diameter offers the best results, which is due to the interactions of sorbate-sorbent on the surface. This behavior can be attributed to the relationship between the effective specific surface area of the adsorbent particles and the size of the particles [58; 59]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Parameters (\%)** & **CP [49]** & **YP [50]** & **OPB [50]** & **CCR [51]** & **CH [52]** & **Method** \\ \hline Cellulose & 18.47 & 13.08 & 19.90 & 13.08 & 19.82 & Digestion-thermogravinetry \\ Hemicellulose & 6.01 & 6.47 & 7.00 & 6.47 & 9.45 & Digestion-thermogravinetry \\ Lignin & 2.20 & 27.73 & 17.11 & 6.51 & 12.66 & Photocolorimetry \\ Pectin & 2.84 & 10.98 & 4.88 & 7.98 & 9.54 & Acid digestion-thermogravinetry \\ Carbon & 39.96 & 48.14 & 38.27 & 39.89 & 50.35 & AOAC 949.14 \\ Hydrogen & 3.98 & 5.44 & 4.71 & 3.28 & 5.08 & AOAC 949.14 \\ Nitrogen & 0.26 & 0.18 & 0.18 & 0.46 & 1.28 & AOAC 949.13-Kjeldahl \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Compositional and bromatological analysis of the biomasses. Increasing the amount of the evaluated adsorbents in contact with the Cd\({}^{2+}\) ions contaminated solution has a negative effect on the adsorption capacity when particle sizes are larger than 0.5 when using OPB, CCR, YP, CH and CP, which may be due to the decrease of the surface area available for ion exchange due to the increase in particle size [60]. This behavior is due to the high availability of active sites in bioadsorbents because of the presence of the hydroxyl, carbonyl, amine and unsaturated hydrocarbon groups characteristic of lignocellulosic materials [61; 62; 63]. These findings were compared with previous publications for the removal of heavy metal ions using biomasses such as the selected in this work.