Evaluation of acyclovir adsorption on granular activated carbon from aqueous solutions: batch and fixed-bed parametric studies

In this study, the adsorption potential of walnut shells (WNS) was investigated using batch and fixed-bed column. Activated carbons (ACs) were prepared from WNS as a precursor for by chemical activation with H3PO4 and KOH with different impregnation ratios for removing reactive red 198 from wastewater. The surface characteristics of the prepared ACs were determined by the analysis of N2 adsorption isotherms (BET), ultimate, proximate and elemental analysis, Fourier transform Infrared spectroscopy, scanning electron microscopy, and acid–base Boehm titration. BET measurements showed that AC-H3.5 has the highest BET surface area (1980 m2/g). Batch adsorption studies were performed to evaluate the effect of pH (3–9), adsorbent dosage (0.5–2.5 g/L), and contact time on the adsorption capacity of WNS for the ACs obtained under optimum conditions. The adsorption kinetics followed the pseudo-second-order model. The equilibrium analysis revealed that the adsorption data was successfully fitted with the Langmuir isotherm. The maximum adsorption capacity calculated by Langmuir isotherm was 79.15 mg/g. Also, enthalpy, entropy, and free Gibbs energy changes showed that the reaction was endothermic. The effects of different bed heights, flow rates and the initial concentrations of dye on the breakthrough characteristics in fixed-bed adsorption column were investigated. Moreover, the Thomas, Yan and bed depth service time (BDST) models were used to predict the breakthrough curves of each component. The R2 of Thomas and Yan model were more than 0.95 and the R2 of BDST model was more than 0.96, also, the adsorption capacity calculated by both models corresponded with experimental values. Also a decrease in flow rate resulted in an increase in the bed volumes with a higher empty bed residence time at the breakthrough.

Functionalized SBA-15 mesoporous silica by melamine-based dendrimer amines for adsorptive characteristics of Pb(II), Cu(II) and Cd(II) heavy metal ions in batch and fixed bed column

The adsorption of cobalt ions from aqueous solution using multiwalled carbon nanotube/polypyrrole modified with NaBH4: Batch and fixed-bed studies

This study described adsorption of Reactive Red120 (RR120) by cotton shell and neem bark in batch and fixed-bed column modes at 293 K. The kinetic and equilibrium of adsorption in batch mode were studied. Nonlinear regressive method was used to obtain relative parameters of adsorption models. The kinetic process was better described by a -first-order kinetic model. The equilibrium adsorption was effectively described by Freundlich and Langmuir adsorption isotherm. The value of C1 from the Langmuir model was 34.375, (RR120 by NB), 33.33, (RR120 by CS), mg/g, Langmuir adsorption intensity Kd had value of 0.2909,(RRNB), 0.25, (RRCS) and the value of Freundlich adsorption capacity Kf is 2.664 (1/n)=0.38(RR120 NB), 2.691 (1/n)=0.44(RR120 CS) . In fixed-bed column adsorption, the effects of bed height, feed flow rate, and inlet Reactive Red120(RR120) concentration were studied by assessing breakthrough curve. The column data were fitted by the Thomas, Clark and modified dose-response models. The modified dose-response model was best to fit the breakthrough curves at experimental conditions. Box behnken design was successfully employed for experimental design and analysis of the results. The combined effect of pH, temperature and Dye concentatration on the dye adsorption was investigated and optimized using response surface methodology. The optimum pH, temperature, and dye concentration were found to be 6.46,32.22°C and 12.60 for Reactive Red120(RR120) by cotton Shell and the optimum pH, temperature, and dye concentration were found to be 6.37, 30.82°C and 11.65 for Reactive Red120(RR120) by neem bark.The results were implied that cotton shell and neem bark may be suitable as an adsorbent material for adsorption of Reactive Red(RR120) from an aqueous solution.

Thiol-incorporated activated carbon derived from fir wood sawdust as an efficient adsorbent for the removal of mercury ion: Batch and fixed-bed column studies

Removal of amoxicillin from water by adsorption onto activated carbon in batch process and fixed bed column: Kinetics, isotherms, experimental design and breakthrough curves modelling

A study on adsorption of cadmium(II) ions from aqueous solution using Luffa cylindrica

Two hydrogels were synthesized, characterized, and applied as alternative materials to remove melamine (MEL) from aqueous media by adsorption. For the first time, a complete study of MEL adsorption is presented, including optimization, kinetics, isotherm, reuse, and column studies with these new materials. One hydrogel is based on xylan and poly (acrylic acid) and was named HXy, and the other is based on the same components functionalized with activated carbon and was named HXy-AC. The materials were synthesized by free radical polymerization and characterized by FTIR, XRD, TGA, DSC, SEM, zeta potential, point of zero charge, N2 adsorption isotherms (BET), helium gas pycnometry, Archimedes method, swelling analysis, and stability tests. The characterization results confirmed the intended synthesis and showed the thermal, morphological, textural, structural, and compositional profile, as well as the adsorption characteristics of the materials. The adsorption studies in batch process included experimental design, kinetics, isotherms, and recyclability, and in continuous mode, the studies included fixed-bed column experiments. The full factorial design showed that adsorbent dosage, pH, and ionic strength are significant for adsorption capacity and removal percentage responses. Doehlert design enabled the definition of the values of adsorbent dosage and pH that were most suitable for MEL adsorption into the materials, indicating the optimal adsorption conditions. The kinetics were well described by the pseudo-first-order model, with R2 above 0.9920 for both materials at all concentrations tested. The isotherm obeyed the Langmuir model, with R2 above 0.9939 for both materials at all temperatures tested. Equilibrium was attained at 180 min, and the maximum experimental adsorption capacity was up to 132.46 and 118.96 mg g-1 at pH 7, with adsorbent dosage of 0.5 g L-1, and 298 K for HXy and HXy-AC, respectively. Furthermore, HXy and HXy-AC materials maintained about 58 and 70% of their initial adsorption capacity at the end of five adsorption/desorption cycles, respectively. Breakthrough curves were described by the Yan model and presented a maximum adsorption capacity of 30.2 and 30.4 mg g-1, treating 3.4 and 6.1 L of influent until the breakthrough point of 0.5 mg L-1 with HXy-AC using 2.0 and 4.0 g of material, respectively. These findings show that the hydrogels produced present the potential to be applied in the adsorption of basic molecules, such as MEL.

The present article explores the ability of five different combinations of two adsorbents (Arachis hypogea shell powder and Eucalyptus cameldulensis saw dust) to remove Pb(II) from synthetic and lead acid batteries wastewater through batch and column mode. The effects of solution pH, adsorbent dose, initial Pb(II) concentration and contact time were investigated with synthetic solutions in batch mode. The Fourier transform infrared spectroscopy study revealed that carboxyl and hydroxyl functional groups were mostly responsible for the removal of Pb(II) ions from test solutions. The kinetic data were found to follow pseudo-second-order model with correlation coefficient of 0.99. Among Freundlich and Langmuir adsorption models, the Langmuir model provided the best fit to the equilibrium data with maximum adsorption capacity of 270.2 mg g−1. Column studies were carried out using lead battery wastewater at different flow rates and bed depths. Two kinetic models, viz. Thomas and Bed depth service time model, were applied to predict the breakthrough curves and breakthrough service time. The Pb(II) uptake capacity (q e = 540.41 mg g−1) was obtained using bed depth of 35 cm and a flow rate of 1.0 mL min−1 at 6.0 pH. The results from this study showed that adsorption capacity of agricultural residues in different combinations is much better than reported by other authors, authenticating that the prepared biosorbents have potential in remediation of Pb-contaminated waters.

Dynamic adsorption of phenolic compounds on activated carbon produced from pulp and paper mill sludge: experimental study and modeling by artificial neural network (ANN)

In this study, removal of phosphate (PO43−) from aqueous solutions using waste mussel shell (WMS) was examined. The physicochemical characteristics of WMS were identified. In the batch experiments, the effects of contact time and adsorbent dosage (m) on the PO43− adsorption by the WMS were scrutinised. The maximum PO43− removal efficiency (E) was 83.4% at 144 h contact time for WMS dosage of 10 g. A comparison of kinetic models applied to the adsorption of PO43− onto WMS was evaluated using pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models. The experimental data was fitted well with the PSO kinetic model. In the isotherm studies, Langmuir and Freundlich isotherm models were applied. The Langmuir isotherm model was well described with the PO43− adsorption. The results indicated that WMS has a good potential to adsorb PO43− from water and thus could improve environmental quality. Furthermore, this study investigated on how the Langmuir isotherm for basic adsorption could be applied to predict E or required m under a given set of initial conditions (i.e., initial solute concentration, solution volume, and adsorbent dosage). This was accomplished by combining the Langmuir isotherm with mass balance of solutes between liquid solution and solid adsorbent phases.

Various nanomaterials have been envisaged mainly through batch studies for environmental remediation application. The real utilization of these new generation adsorbents in large scale pose a difficulty due to its low density and small size which makes it difficult for isolation after application. In this context, nanoadsorbents polymer composite beads can be seen as a way out. Here, functionalized CNTs (carbon nanotubes) have been fabricated into micro beads with sodium alginate. The alginate-functionalized CNT (Alg-f-CNT) beads were then comprehensively evaluated for batch and fixed-bed column separation of divalent mercury ions from an aqueous medium. The effects of process parameters such as pH, contact time, feed Hg2+ concentration, and temperature were studied. Simulation of the experimental data suggested that adsorption is an endothermic spontaneous process which follows the pseudo-second-order kinetic and Langmuir isotherm model. The desorption of the Hg2+ ion from used adsorbent was possible with 1 M HNO3. The breakthrough curves at different process parameters were investigated during fixed-bed column separation and found to be in good agreement with Thomas model. The regeneration and reusability of the adsorbent were tested up to five cycles without a significant decrease in the removal performance. Density functional theory studies revealed stronger interaction of Alg-f-CNT with Hg compared to free alginic acid and established the role of carboxyl and oxo groups present in the adsorbent in the coordination of the Hg2+ ions. The experimental results demonstrate that functionalized CNT-encapsulated alginate beads are a promising alternate material, which can be used to remove mercury in the fixed-bed column mode of the operation.

Highly efficient as-synthesized and oxidized multi-walled carbon nanotubes for copper(II) and zinc(II) ion adsorption in a batch and fixed-bed process

Preparation and characteristics of CuO/γ-Al2O3 nanocomposite as efficient adsorbent for adsorption of sulfur compounds from Iraqi naphtha

Removal of azo dye Direct Blue 71 (DB71), from aqueous solution using synthesized nickel ferrite nanoparticles (NFN) (NiFe2O4) supported on Clinoptilolite zeolite (CP) was studied. The prepared NFN-CP were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray (EDX), and Brunauer–Emmett–Teller (BET) surface area analysis. The kinetic and isotherm of dye adsorption was studied. The effects of operational parameter such as: pH, adsorbent dosage and contact time on the process were studied and optimized. The results showed that pH 6, adsorbent dosage 0.12 g, contact time 45 min was optimum conditions for adsorption process. The results showed that the dye adsorption onto CP and NFN-CP followed Langmuir isotherm. Adsorption kinetics of DB71 onto the NFN-CP followed the pseudo-second-order kinetic model.