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ABSTRACT
Adsorption of Ni(II) onto blue-green marine algae (BGMA) is investigated under batch condition. Under optimum experimental conditions, the initial Ni(II) metal ion concentration is varied from 25 to 250 ppm and the maximum adsorption capacity of BGMA is found to be 42.056 mg/g. The optimum pH, biomass loading, and an agitation rate on maximum removal of Cu(II) ion are found to be 6, 2 g, and 120 rpm, respectively. 24 h of contact time is allowed to achieve equilibrium condition. All the experiments are carried out at room temperature. The equilibrium experimental data infer that the isotherm is L-shaped. It is the indication of no strong competition between solvent and Ni(II) to occupy the active sites of BGMA. Also, it indicates that the BGMA has a limited sorption capacity for adsorption of Ni(II). The experimental data are tested with various isotherm models; subsequently, the mechanism of adsorption is identified and the characteristic parameters for process design are established. Fritz–Schlunder-V isotherm model is highly significant in establishing the mechanism of adsorption of Ni(II) under the conditions employed in this investigation followed by Freundlich. The qmax of 41.89 mg/g obtained by this model indicates its relevance more precisely with experimental data.
Nomenclature
| A | = | Fritz–Schlunder parameter |
| aF | = | Freundlich adsorption capacity (L/mg) |
| AHJ | = | Harkin–Jura isotherm constant |
| aK | = | Khan isotherm model exponent |
| AKC | = | Koble–Carrigan’s isotherm constant |
| ARP | = | Redlich–Peterson isotherm constant (L/g) |
| AT | = | Temkin equilibrium-binding constant corresponding to the maximum binding energy |
| B | = | Fritz–Schlunder parameter |
| BGMA | = | blue-green marine algae |
| b | = | Langmuir constant related to adsorption capacity (L/mg) |
| b0 | = | Langmuir isotherm equilibrium constant |
| BDR | = | Dubinin–Radushkevich model constant |
| BHJ | = | Harkin–Jura isotherm constant |
| bJ | = | Jossens isotherm model parameter |
| bK | = | Khan isotherm model constant |
| BKC | = | Koble–Carrigan’s isotherm constant |
| bL | = | Langmuir constant related to adsorption capacity (mg/g) |
| BRP | = | Redlich–Peterson isotherm constant (L/mg) |
| bT | = | Temkin constant which is related to the heat of sorption (J/mol) |
| C | = | Henry’s law model intercept |
| Ceq | = | concentration of adsorbate in bulk solution at equilibrium (mg/L) |
| Cin | = | initial adsorbate concentration (mg/L) |
| J | = | Jossens isotherm model parameter |
| K | = | Henry’s constant |
| K1 | = | Hill–de Boer constant (L/mg) |
| K1FS5 | = | Fritz–Schlunder-V parameter |
| K2 | = | energetic constant of the interaction between adsorbed molecules (kJ/mol) |
| K2FS5 | = | Fritz–Schlunder-V parameter |
| KBS | = | Brouers–Sotolongo model isotherm parameter |
| KDR | = | Dubinin–Radushkevich model uptake capacity |
| KE | = | Elovich constant (L/mg) |
| KFG | = | Fowler–Guggenheim equilibrium constant (L/mg) |
| KFH | = | Flory–Huggins equilibrium constant (L/mol) |
| KFS3 | = | Fritz–Schlunder III equilibrium constant (L/mg) |
| KH | = | Hill isotherm constant |
| KHa | = | Halsey isotherm constant |
| KHe | = | Henry’s constant |
| KHK | = | Holl–Krich isotherm model parameter |
| KJ | = | Jossens isotherm model parameter |
| KJ | = | Jovanovic constant |
| KJF | = | Jovanovic–Freundlich isotherm equilibrium constant |
| KK | = | Kiselev equilibrium constant (L/mg) |
| KLF | = | Langmuir–Freundlich equilibrium constant for heterogeneous solid |
| KLJ | = | Langmuir–Jovanovic model parameter |
| KMJ | = | Marczewski–Jaroniec isotherm model parameter that characterizes the heterogeneity of the adsorbent surface |
| KnK | = | equilibrium constant of the formation of complex between adsorbed molecules |
| KRaP | = | Radke–Prausnits equilibrium constant |
| KS | = | Sips isotherm model constant (L/mg) |
| KT | = | Toth isotherm constant (mg/g) |
| KU | = | Unilan isotherm model parameter |
| KVS | = | Vieth–Sladek isotherm model parameter related to Henry’s law |
| mFS3 | = | Fritz–Schlunder-III model exponent |
| mLF | = | Langmuir–Freundlich heterogeneity parameter |
| mRaP | = | Radke–Prausnits model exponent |
| nF | = | Freundlich adsorption intensity |
| nFH | = | number of adsorbates occupying adsorption sites |
| nH | = | exponent of Hill adsorption model |
| nHa | = | Halsey isotherm exponent |
| nHK | = | Holl–Krich Isotherm model exponent |
| nJF | = | Jovanovic–Freundlich isotherm exponent |
| nKC | = | Koble–Carrigan’s isotherm constant |
| nLJ | = | Langmuir–Jovanovic model exponent |
| nMJ | = | Marczewski–Jaroniec isotherm model parameter that characterizes the heterogeneity of the adsorbent surface |
| nT | = | Toth isotherm exponent |
| P1 | = | Weber and van Vliet isotherm model parameter |
| P2 | = | Weber and van Vliet isotherm model parameter |
| P3 | = | Weber and van Vliet isotherm model parameter |
| P4 | = | Weber and van Vliet isotherm model parameter |
| qeq | = | amount of adsorbate in adsorbent at equilibrium (mg/g) |
| qmax | = | maximum quantity of solute adsorbed by the adsorbent (mg/g) |
| R | = | gas constant (8.314 J/mol K) |
| RL | = | Langmuir separation factor |
| RL | = | Langmuir separation factor |
| T | = | absolute temperature (K) |
| W | = | interaction energy between adsorbed molecules (kJ/mol) |
| x | = | Baudu isotherm model parameter |
| y | = | Baudu isotherm model parameter |
Greek letters
| θ | = | fractional surface coverage |
| βRP | = | Redlich–Peterson isotherm exponent |
| βS | = | Sips isotherm exponent |
| αBS | = | Brouers–Sotolongo model isotherm parameter is related to adsorption energy |
| βVS | = | Vieth–Sladek isotherm model parameter related to Langmuir |
| βU | = | Unilan isotherm model exponent |
| αFS5 | = | Fritz–Schlunder-V parameter |
| β2FS5 | = | Fritz–Schlunder-V parameter |