*Removal of Divalent Nickel from Aqueous Solution Using Blue Green Marine Algae… DOI: http://dx.doi.org/10.5772/intechopen.103940*


**Table 4.**

*Parameter values of three parameter isotherm models for adsorption of Ni(II) onto BGMA.*

Freundlich, Fritz-Schlunder-III, Radke-Prausnits, and Jossens isotherm models have low R<sup>2</sup> values. However, the models Sips, Radke-Prausnits -I, Radke-Prausnits -III, Toth, Khan, Koble-Corrigan, Jovanovic-Freundlich, Brouers-Sotolongo, Vieth-Sladek, Unilan, Holl-Krich, and Langmuir-Jovanovic isotherm models demonstrate their relevance by strong R<sup>2</sup> values, however the parameter and qmax (mg/g) values produced are either negative or excessively high, implying that they are not physically realisable. As a result, all 16 models are dropped from the ongoing debate.

qmax 820.8

#### *4.2.4 Four parameter models*

**Table 5** shows the parameter and R2 values for four parameter isotherm models. To understand the adsorption mechanism of Ni(II) onto BGMA, the Fritz-Schlunder-IV isotherm model, Baudu isotherm model, Weber-van Vliet isotherm model, and Marczewski-Jaroniec isotherm model are investigated.

The Baudu and Fritz-Schlunder-IV models, which have higher R2 values than the Weber-van Vliet and Marczewski-Jaroniec models, are the most significant of the four models. Unfortunately, the exponents and parameters of all four models are either zero, very low, or excessively high, making them physically impossible to realise. Like a result, just as in the case of the three parameter models, all four parameter models fail to describe the process of adsorption, and the discussion is unnecessary.


*Removal of Divalent Nickel from Aqueous Solution Using Blue Green Marine Algae… DOI: http://dx.doi.org/10.5772/intechopen.103940*

#### **Table 5.**

*Parameter values of four parameter isotherm models for adsorption of Ni(II) onto BGMA.*


**Table 6.**

*Parameter values of five parameter isotherm model for adsorption of Ni(II) onto BGMA.*

### *4.2.5 Five parameter model*

**Table 6** shows the Fritz-Schlunder-V model's parameter values. The R2 value denotes its relevance. **Figure 7** depicts a comparison of experimental Ni(II) metal uptake with the Fritz-Schlunder-V model under equilibrium conditions. **Figure 8** depicts the agreement of Fritz-Schlunder-V parameter model results for equilibrium Ni(II) uptake with experimental data.

The qmax value of 41.89 mg/g for this isotherm model is extremely similar to the experimental qmax value of 42.056 mg/g. As a consequence, the Fritz-Schlunder-V isotherm model is firmly established for the adsorption of Ni(II) metal ions from synthetic aqueous solution onto BGMA.

**Figure 7.**

*Comparison of experimental values of equilibrium uptake of Ni(II) with five parameter model values.*

**Figure 8.** *Concurrence of five parameter model values of equilibrium uptake of Ni(II) with experimental values.*
