Isothermal, Kinetic, and Thermodynamic Study of Copper Ion Adsorption Using Raw Ranufe Bentonite and Its Sodium and Pillared Forms
Bibliographic record
Abstract
Heavy metals in industrial waste cause environmental damage because they metals are toxic, nonbiodegradable, and are bioaccumulated. As such, treatments are needed to reduce heavy metals to legally acceptable levels before disposal. As such, the aim of this study was to assess copper ion adsorption in aqueous solution using Ranufe bentonite (raw, sodium and pillared), which is abundant in Northeastern Brazil. Sodium bentonite was obtained using ionic exchange with sodium acetate and pillared bentonite was formulated with a pillarizing agent (aluminum hydroxide and sodium). Treatment efficiency was assessed using Brunauer–Emmett–Teller (BET), X-ray fluorescence (XRF), and X-ray diffraction (XRD) analyses. The surface area obtained by BET showed behavior characteristics of a mesoporous material. XRD exhibited basal spacing consistent with the pattern of clays. XRF analyses confirmed the changes on the raw bentonite surface, proving its transformation in the sodium and pillared forms. Adsorption capacity was assessed as a function of pH, contact time, adsorbent mass, initial metal concentration, ligand and co-ion effects on copper removal efficiency, reaching a maximum rate of 85.76%. Adsorption isotherms were fit to the Langmuir model, assuming adsorption on homogeneous surfaces in the form of monolayers, with maximum adsorption capacity of 12.92 mg/g−1 (raw bentonite) and 24.51 mg/g−1 (sodium bentonite). The kinetic study demonstrated that bentonite (raw and sodium) fit the pseudo-second-order kinetic model, indicating a process governed by ionic exchange between copper and the ions present in the bentonite layers. The thermodynamic adsorption parameters demonstrated that adsorption using raw and sodium bentonite is endothermic (favored by the rise in temperature) and nonspontaneous (energy is needed to promote adsorption). In a study on desorption, four adsorption and desorption cycles were sufficient to assess the regeneration capacity of the material, showing a decrease in adsorption capacity from the first to last cycle from 69.47% to 41.33% (raw bentonite) and from 48.36% to 22.46% (sodium bentonite). A decline in adsorption capacity is related to chemical degradation caused by acid solutions and mechanical agitation during the adsorption cycles.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".