The need to design low-cost adsorbents for the detoxification of industrial effluents has been a growing concern for most environmental researchers. So modelling of experimental data from adsorption processes is a very important means of predicting the mechanisms of various adsorption systems. Therefore, this paper presents an overall review of the applications of adsorption isotherms, the use of linear regression analysis, nonlinear regression analysis, and error functions for optimum adsorption data analysis.
A complete study of adsorption processes will be less complete if the structure and dynamics of its different elements and how they interact is not well captured. Therefore, the extensive study of adsorption thermodynamics in conjunction with adsorption kinetics is inevitable. Measurable thermodynamic properties such as temperature equilibrium constant and their non-measurable counterparts such as Gibbs free energy change, enthalpy, entropy etc. are very important design variables usually deployed for the evaluation and prediction of the mechanism of adsorption processes.
The effect of some acids, anions and auxiliary complexing agents on the extraction of Cadmium (II) from aqueous solutions buffered to pH 7.5 using a chloroform solution of the Schiff base ligand 4,4´-(1E,1E´)-1,1´-(ethane-1,2-diylbis(azan-1-yl-1ylidene))bis(5-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-ol) (H2BuEtP) alone and in the presence of 1-(3-hydroxy-5-methyl-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl) butan-1-one (HBuP) after an equilibration time of sixty minutes was investigated. Working concentration of Cd(II) was 50mgL-1, while a range from 0.001M-3.0M was used for acid and 0.001M-1.0M for anions and auxiliary complexing agents. Extraction raffinates were analysed for Cd(II) using Flame Atomic Absorption spectrophotometry and Distribution Ratios. Percentage Extractions (%E) were calculated by difference of Cd(II) concentrations before and after equilibration. The mixed ligands H2BuEtP/HBuP organic phase was a better extractant for Cadmium than H2BuEtP alone but the difference was not significant for all acids, Cl-, Oxalate and Tartrate. The results indicated that at lower concentrations of the acids, anions and auxiliary complexing agents, a releasing effect occurred with improved extraction of Cadmium > 90% in most cases and at high concentrations there was reduced percentage extraction due to masking of Cadmium from formation of stable salts of Cadmium. Comparing results with other those of other metals studied under same conditions showed that multi-metal extraction with the ligand (H2BuEtP) is possible. H3PO4, H2SO4, HCl, PO43-, EDTA and Oxalate all showed theoretical potentials for separating Cadmium from other studied metals with Separation Factors βxy = Dx/Dy close to and above 104.
In this study, a magnetic generation-5 polyamidoamine (G-5 PAMAM) dendrimer-functionalized SBA-15 (mPSBA) composite was synthesized by coupling amine-functionalized silica (SBA-15-NH 2 ) and amine-functionalized magnetic nanoparticles (MNP-NH 2 ) with the G-5 PAMAM, before characterization and aqueous sorption of As(III), Cd(II), tetracycline, and ciprofloxacin using the composite. The mPSBA characterization data exhibited the typical Si−O−Si infrared peaks from the SBA-15 backbone in addition to the acquired characteristic infrared Fe−O and amide-I/II peaks from the MNP and G-5 PAMAM dendrimers, respectively. Postsorption infrared spectra showing shifts for the amide-linked groups indicated the likely points of contaminant attachment on the composite. Its thermal stability was lower than that of SBA-15 but higher than that of SBA-15-NH, while the XRD diffractograms of the backbone SBA-15-NH and MNP were unchanged in the final composite. The mPSBA composite was a better As(III) and Cd(II) adsorbent than SBA-15 by ≈400 and 140%, respectively, with rapid uptake in the first 60 min and equilibrium achieved at 120 min. Sorption was enhanced with increasing pH (until pHpzc) and initial contaminant concentration. The process was spontaneous and endothermic; thus, increasing ambient temperature enhanced Cd(II) sorption. The sorption data fitted better to the homogeneous fractal pseudo-second-order (FPSO) kinetics model and the Brouers−Sotolongo fractal adsorption isotherm models, indicating complex sorption interactions and pore-filling/contaminant trapping within mPSBA. Further experiments using mPSBA for the uptake of tetracycline and ciprofloxacin showed 679% and 325% higher sorption, respectively, compared with that for SBA-15-NH. In addition to the added advantage of easy removal from solution/treated water after the adsorption process, mPSBA sorption capacities for these studied contaminants [As(III): 23.3 mg/g; Cd(II): 74.5 mg/g; tetracycline: 38.4 mg/g; ciprofloxacin: 23.0 mg/g] are better than those of several advanced adsorbents reported in the literature.
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