Model-Based and Molecular-Level Evaluation of Methyl Orange Adsorption onto a Hazelnut Shell-Based Carbonaceous Adsorbent

Öz

This study presents a combined model-based and molecular-level assessment of methyl orange uptake by a hazelnut shell-based carbonaceous adsorbent. Batch experiments were conducted under previously optimized conditions, namely a dye concentration of 42.65 mg/L, adsorbent loading of 1.29 g/L, temperature of 30.4 °C, and pH 3.0. Kinetic, diffusion, equilibrium, apparent thermodynamic, surface charge, Fourier-transform infrared spectroscopy, and density functional theory analyses were used to evaluate the macroscopic adsorption behavior and to support possible molecular interaction pathways. The nonlinear pseudo-first-order model provided the most suitable empirical description of the kinetic profile, yielding qe = 32.62 ± 0.51 mg/g, k1 = 1.28 × 10−2 ± 5.63 × 10−4 min−1, and R2 = 0.9963. Weber–Morris and Boyd analyses suggested that the uptake behavior was consistent with coupled surface attachment, film diffusion, and intraparticle diffusion rather than a single rate-controlling step. Freundlich modeling suggested a heterogeneous adsorption description, with the Freundlich constant increasing from 15.05 to 46.09 (mg/g)(L/mg)1/n and n rising from 2.24 to 3.37 with increasing temperature. Negative apparent Gibbs free energy changes and positive apparent enthalpy and entropy changes suggested a favorable, endothermic, and entropy-favored tendency under the investigated conditions. Surface charge measurements, infrared spectral changes, and quantum chemical results collectively supported the possibility that acidic conditions favored electrostatic attraction, while π–π stacking, dispersion forces, and localized hydrogen bonding may have contributed to stabilization of the adsorbed state. Overall, the hazelnut shell-based carbonaceous adsorbent exhibited effective dye-removal performance, as supported by combined experimental and computational evidence.

Anahtar Kelimeler

• Adsorption modelling
• apparent thermodynamics
• density functional theory
• hazelnut shell-derived carbon
• methyl orange
• water treatment

Destekleyen Kurum

This study received no financial support.

Etik Beyan

This study did not involve human participants, animals, or clinical data. Therefore, ethical approval was not required.

Teşekkür

The numerical calculations reported in this paper were partially performed at TUBİTAK ULAKBİM, High Performance and Grid Computing Center using TRUBA resources.

Metil Turuncusunun Fındık Kabuğu Temelli Karbonlu Bir Adsorban Üzerine Adsorpsiyonunun Model Tabanlı ve Moleküler Düzeyde Değerlendirilmesi

Öz

Bu çalışma, metil turuncusunun fındık kabuğu temelli karbonlu bir adsorban tarafından tutulmasını model tabanlı ve moleküler düzeyde birlikte değerlendirmektedir. Kesikli sistem deneyleri daha önce optimize edilen koşullar altında yürütülmüştür: boya derişimi 42,65 mg/L, adsorban dozu 1,29 g/L, sıcaklık 30,4 °C ve pH 3,0. Kinetik, difüzyon, denge, görünür termodinamik, yüzey yükü, Fourier dönüşümlü kızılötesi spektroskopisi ve yoğunluk fonksiyoneli teorisi analizleri, makroskobik adsorpsiyon davranışını değerlendirmek ve olası moleküler etkileşim yollarını desteklemek amacıyla kullanılmıştır. Doğrusal olmayan yalancı birinci derece model, kinetik profili en uygun şekilde tanımlamış; qe = 32,62 ± 0,51 mg/g, k1 = 1,28 × 10⁻² ± 5,63 × 10⁻⁴ min⁻¹ ve R² = 0,9963 değerlerini vermiştir. Weber–Morris ve Boyd analizleri, adsorpsiyon davranışının tek bir hız sınırlayıcı basamaktan ziyade yüzey tutunması, film difüzyonu ve partikül içi difüzyonun birlikte etkisiyle uyumlu olduğunu göstermiştir. Freundlich modellemesi heterojen bir adsorpsiyon davranışına işaret etmiş; Freundlich sabiti sıcaklık artışıyla 15,05’ten 46,09 (mg/g)(L/mg)¹/ⁿ değerine, n değeri ise 2,24’ten 3,37’ye yükselmiştir. Negatif görünür Gibbs serbest enerji değişimleri ile pozitif görünür entalpi ve entropi değişimleri, incelenen koşullar altında adsorpsiyonun elverişli, endotermik ve entropi destekli bir eğilim gösterdiğini düşündürmektedir. Yüzey yükü ölçümleri, kızılötesi spektral değişimler ve kuantum kimyasal sonuçlar birlikte değerlendirildiğinde, asidik koşulların elektrostatik çekimi desteklediği; π–π istiflenmesi, dispersiyon kuvvetleri ve lokalize hidrojen bağlarının ise adsorplanmış durumun kararlılığına katkı sağlamış olabileceği görülmektedir. Genel olarak, fındık kabuğu temelli karbonlu adsorban, deneysel ve hesaplamalı kanıtlarla desteklenen etkili bir boya giderim performansı sergilemiştir.

Anahtar Kelimeler

• Adsorpsiyon modellemesi
• görünür termodinamik
• yoğunluk fonksiyoneli teorisi (DFT)
• fındık kabuğundan türetilmiş karbon
• metil turuncusu
• su arıtımı

Destekleyen Kurum

Bu çalışma için herhangi bir finansal destek alınmamıştır.

Etik Beyan

Bu çalışmada insan katılımcılar, hayvanlar veya klinik veriler yer almamıştır. Bu nedenle etik kurul onayı alınmasına gerek duyulmamıştır.

Teşekkür

Bu makalede sunulan sayısal hesaplamaların bir kısmı, TÜBİTAK ULAKBİM Yüksek Başarımlı ve Grid Hesaplama Merkezi bünyesindeki TRUBA kaynakları kullanılarak gerçekleştirilmiştir.

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