A novel route for preparation of chemically activated carbon from pistachio wood for highly efficient Pb(II) sorption.

Pistachio wood-derived activated carbon prepared by a two-stage process (PWAC-2), conducting two consecutive chemical activation processes with NH4NO3 and NaOH, respectively. The results showed that explosive characteristic of NH4NO3 can primarily be employed to produce a char, with a large surface area and a highly-ordered pore structure, which can be subjected to a second activation process with NaOH to prepare a more suitable activated carbon, with a highly porous structure and useful functional groups, for removal of lead ions from aqueous media. An L25 Taguchi experimental design was used by varying impregnation ratio, activation time and temperature in both pre- and post-activation stages, and the results showed that, in both stages, a small activating agent/precursor and a proportional low activation time suffice for preparation of an advantageous activated carbon for Pb(II) adsorption. A comprehensive study was performed on the equilibrium, kinetic and thermodynamic aspects of Pb(II) adsorption by the new activated carbon. The results exhibited that, having had a high lead adsorption capacity (190.2 mg g-1), a high adsorption rapidness, and thermodynamic favorability, PWAC-2 is a beneficial alternative for utilization in full-scale plants of lead removal from waters and wastewaters.

Experimental and modeling of potassium diclofenac uptake on activated carbon.

The presence of pharmaceuticals in wastewater resulting from human activities has driven researchers to explore effective treatment methods such as adsorption using activated carbon (AC). While AC shows promise as an adsorbent, further studies are essential to comprehend its entire interaction with pharmaceuticals. This article investigates the adsorption of potassium diclofenac (PD) onto AC using experimental and modeling approaches. Batch adsorption studies coupled with Fourier transform infrared spectroscopy (FTIR) were employed to clarify the adsorption mechanism of PD on AC. Various kinetic and isotherm adsorption models were applied to analyze the adsorbent-adsorbate interaction. The kinetics were best described by Avrami's fractional order (AFO) nonlinear model. Also, the intraparticle diffusion (IP) model reveals a three-stage adsorption process. The experimental equilibrium data fitted well with the three-parameter nonlinear Liu model, indicating a maximum adsorption capacity (Qmax) of 88.45 mg g-1 and suggesting monolayer or multilayer adsorption. Thermodynamic analysis showed favorable adsorption (ΔG° < 0), with an enthalpy change (ΔH° = -30.85 kJ mol-1) characteristic of physisorption involving hydrogen bonds and π-π interactions. The adsorption mechanism was attributed to forming a double layer (adsorbate-adsorbent and adsorbate-adsorbate).

Hydrochar as a bio-based adsorbent for heavy metals removal: A review of production processes, adsorption mechanisms, kinetic models, regeneration and reusability.

The spread of heavy metals throughout the ecosystem has extremely endangered human health, animals, plants, and natural resources. Hydrochar has emerged as a promising adsorbent for removal of heavy metals from water and wastewater. Hydrochar, obtained from hydrothermal carbonization of biomass, owns unique physical and chemical properties that are highly potent in capturing heavy metals via surface complexation, electrostatic interactions, and ion exchange mechanisms. This review focuses on removing heavy metals by hydrochar adsorbents from water bodies. The article discusses factors affecting the adsorption capacity of hydrochars, such as contact time, pH, initial metal concentration, temperature, and competing ions. Literature on optimization approaches such as surface modification, composite development, and hybrid systems are reviewed to enlighten mechanisms undertaking the efficiency of hydrochars in heavy metals removal from wastewater. The review also addresses challenges such as hydrochar regeneration and reusability, alongside potential issues related to its disposal and metal leaching. Integration with current water purification methods and the significance of ongoing research and initiatives promoting hydrochar-based technologies were also outlined. The article concludes that combining hydrochar with modern technologies such as nanotechnology and advanced oxidation techniques holds promise for improving heavy metal remediation. Overall, this comprehensive analysis provides valuable insights to guide future studies and foster the development of effective, affordable, and environmentally friendly heavy metal removal technologies to ensure the attainment of safer drinking water for communities worldwide.

Statistics design for the synthesis optimization of lignin-sulfonate sulfur-doped mesoporous carbon materials: promising candidates as adsorbents and supercapacitors materials.

This study employed lignin-sulfonated (LS) to develop biobased carbon materials (LS-Cs) through a sulfur-doping approach to enhance their physicochemical properties, adsorption capabilities, and energy storage potentials. Various characterization techniques, including BET surface area analysis, SEM imaging, XPS, Raman spectroscopy, and elemental composition (CHNS), were employed to assess the quality of the LS-Cs adsorbent and electrode samples. Response Surface Methodology (RSM) was utilized for optimizing the two main properties (specific surface area, ABET, and mesopore area, AMESO) by evaluating three independent factors (i.e., activation temperature, ZnCl2:LS ratio, and sulfur content). According to the statistical analysis, ABET and AMESO were affected by ZnCl2 and sulfur content, while the pyrolysis temperature did not affect the responses in the studied conditions. It was found that increasing the ZnCl2 and sulfur contents led to an increment of the ABET and AMESO values. The LS-C materials exhibited very high ABETvalues up to 1993 m2 g-1 and with predominantly mesoporous features. The S-doping resulted in LS-Cs with high sulfur contents in their microstructures up to 15% (wt%). The LS-C materials were tested as adsorbents for sodium diclofenac (DCF) adsorption and reactive orange 16 dye (RO-16) and as electrodes for supercapacitors. The LS-Cs exhibited excellent adsorption capacity values for both molecules (197-372 mg g-1) for DCF, and (223-466 mg g-1) for RO-16. When tested as electrodes for supercapacitors, notably, LS-C3, which is a doped sample with sulfur, exhibited the best electrochemical performance, e.g. high specific capacitance (156 F/g at 50 mV/s), and delivered an excellent capacitance after 1000 cycles (63 F/g at 1 A/g), which denotes the noteworthy capacitive behavior of the S-doped electrode. Thus, the present work suggests an eco-friendly resource for developing effective, productive carbon materials for adsorbent and electrodes for SC application. However, further studies on the complete application of these materials as adsorbents and electrodes are needed for a deeper understanding of their behavior in environmental and energy storage applications.

Synthesis, Characterization, and Adsorption Properties of Nitrogen-Doped Nanoporous Biochar: Efficient Removal of Reactive Orange 16 Dye and Colorful Effluents.

In this work, nitrogen-doped porous biochars were synthesized from spruce bark waste using a facile single-step synthesis process, with H3PO4 as the chemical activator. The effect of nitrogen doping on the carbon material's physicochemical properties and adsorption ability to adsorb the Reactive Orange 16 dye and treat synthetic effluents containing dyes were evaluated. N doping did not cause an important impact on the specific surface area values, but it did cause an increase in the microporosity (from 19% to 54% of micropores). The effect of the pH showed that the RO-16 reached its highest removal level in acidic conditions. The kinetic and equilibrium data were best fitted by the Elovich and Redlich-Peterson models, respectively. The adsorption capacities of the non-doped and doped carbon materials were 100.6 and 173.9 mg g-1, respectively. Since the biochars are highly porous, pore filling was the main adsorption mechanism, but other mechanisms such as electrostatic, hydrogen bond, Lewis acid-base, and π-π between mechanisms were also involved in the removal of RO-16 using SB-N-Biochar. The adsorbent biochar materials were used to treat synthetic wastewater containing dyes and other compounds and removal efficiencies of up to 66% were obtained. The regeneration tests have demonstrated that the nitrogen-doped biochar could be recycled and reused easily, maintaining very good adsorption performance even after five cycles. This work has demonstrated that N-doped biochar is easy to prepare and can be employed as an efficient adsorbent for dye removal, helping to open up new solutions for developing sustainable and effective adsorption processes to tackle water contamination.

Comprehensive adsorption and spectroscopic studies on the interaction of magnetic biochar from black wattle sawdust with beta-blocker metoprolol.

The rise of contaminants of emerging concern in water-resources due to human activities has driven research toward wastewater treatment, specifically adsorption. The utilization of woody biomass for biochar production in adsorption has shown promise due to its high availability. This study shows the preparation of magnetic biochars (MB) from waste black wattle sawdust, utilizing ZnCl2 and NiCl2 (proportions: 1:0.5:0.5 = MB-0.5 and 1:1:1 = MB-1) as activating and magnetic agents. Synthesized via microwave-assisted-pyrolysis, MB boasts a high surface area (up to 765 m2.g-1) and functional groups, enhancing metoprolol medicine adsorption. Nonlinear kinetic and isothermal models were tested; the Avrami fractional-order kinetic model and Liu's isothermal model provided the best fits for experimental data. Thermodynamics and spectroscopic studies revealed spontaneous and exothermic adsorption processes, with physisorption magnitude and dominance of hydrogen-bond and π-π-interactions. MB can be easily extracted from an aqueous medium using magnetic fields, while adsorption capacity could be regenerated through green solvent elution.

Preparation and Characterization of Pulp and Paper Mill Sludge-Activated Biochars Using Alkaline Activation: A Box-Behnken Design Approach.

This study utilized pulp and paper mill sludge as a carbon source to produce activated biochar adsorbents. The response surface methodology (RSM) application for predicting and optimizing the activated biochar preparation conditions was investigated. Biochars were prepared based on a Box-Behnken design (BBD) approach with three independent factors (i.e., pyrolysis temperature, holding time, and KOH:biomass ratio), and the responses evaluated were specific surface area (SSA), micropore area (S micro), and mesopore area (S meso). According to the RSM and BBD analysis, a pyrolysis temperature of 800 °C for 3 h of holding and an impregnation ratio of 1:1 (biomass:KOH) are the optimum conditions for obtaining the highest SSA (885 m2 g-1). Maximized S micro was reached at 800 °C, 1 h and the ratio of 1:1, and for maximizing S meso (569.16 m2 g-1), 800 °C, 2 h and ratio 1:1.5 (445-473 m2 g-1) were employed. The biochars presented different micro- and mesoporosity characteristics depending on pyrolysis conditions. Elemental analysis showed that biochars exhibited high carbon and oxygen content. Raman analysis indicated that all biochars had disordered carbon structures with structural defects, which can boost their properties, e.g., by improving their adsorption performances. The hydrophobicity-hydrophilicity experiments showed very hydrophobic biochar surfaces. The biochars were used as adsorbents for diclofenac and amoxicillin. They presented very high adsorption performances, which could be explained by the pore filling, hydrophobic surface, and π-π electron-donor-acceptor interactions between aromatic rings of both adsorbent and adsorbate. The biochar with the highest surface area (and highest uptake performance) was subjected to regeneration tests, showing that it can be reused multiple times.

Application of a multilayer physical model for the critical analysis of the adsorption of nicotinamide and propranolol on magnetic-activated carbon.

The paper describes a theoretical analysis of the adsorption of nicotinamide and propranolol onto a magnetic-activated carbon (MAC). For a better evaluation of the adsorption mechanism, adsorption isotherms expressing the variation of the adsorption capacity as function of adsorbate concentration were determined at different temperatures ranging from 20 to 45 °C. For both the analytes, experimental tests reveal that adsorption capacity increases with temperature. An advanced multi-layer model derived from the statistical physics is set for the interpretation of the entire adsorption data set. The modelling results show that the propranolol molecules change their adsorption orientation from a mixed (parallel and non-parallel) orientation to a multimolecular process. For nicotinamide, the aggregation of molecules is practically absent, except for the data at lower temperatures. The model allows stating that the adsorption of both the pharmaceutical compounds occurs via the formation of one or two layers on MAC adsorbent, the propranolol showing a higher tendency to form multiple layers. Finally, adsorption energy is estimated suggesting that the adsorption is endothermic and physical interactions are the responsible of the adsorption of both the compounds onto MAC adsorbent.

Purification and economic analysis of nanoclay from bentonite.

Nowadays, due to the most application of montmorillonite, its purification from raw bentonite has great importance. More than 76% of bentonite is composed of montmorillonite, and its industrial applications are related to its montmorillonite content. In this study, the nanoclay was extracted from bentonite by the use of centrifugal force. The results of the field-emission scanning electron microscopy (FE-SEM) analysis show that the nanosized of purified montmorillonite has a sheet structure with a spacing of 22.41 nm and 45.0 nm. The sharp peaks in X-ray diffraction analysis (XRD) illustrated that the montmorillonite purified successfully, and the results of Fourier-transform infrared spectrophotometry (FT-IR) revealed the successful incorporation of the metabolic extraction within the montmorillonite. By comparison of Brunauer-Emmett-Teller (BET) results with IUPAC, it can be realized that the synthesized montmorillonite nanoclay has a microporous structure (< 2 nm) with a surface area of 11.325 m2 g-1. According to IUPAC classification, the BET isotherms of montmorillonite and bentonite indicate a hysteresis loop belonging to the type H3. Finally, the economic analysis results revealed to this method could be the best option for achieving high purity montmorillonite for future applications.

Adsorption mechanism of Zn2+, Ni2+, Cd2+, and Cu2+ ions by carbon-based adsorbents: interpretation of the adsorption isotherms via physical modelling.

A theoretical physicochemical and thermodynamic investigation of the adsorption of heavy metals Zn2+, Cd2+, Ni2+, and Cu2+on carbon-based adsorbents was performed with statistical physics fundaments. Particularly, the experimental adsorption isotherms of heavy metal removal, at 30°C and pH 5, using adsorbents obtained from the pyrolysis of three biomasses (cauliflower cores, broccoli stalks, and coconut shell) were modelled and interpreted with a homogeneous statistical physics adsorption model. Calculations indicated that the heavy metal adsorption with these carbon-based materials was a multi-ionic process where several ions interact simultaneously with the same carboxylic functional group on the adsorbent surface. Adsorption capacities for these metal ions and adsorbents were correlated with electronegativity theory, which established that the adsorbate with the highest electronegativity was more readily adsorbed by the carboxylic functional groups available on the adsorbent surfaces. Also, the chemical compositions of biomass precursors explained achieved adsorption capacities for these metallic ions. The best adsorbent for heavy metal removal was obtained from CC biomass pyrolysis. Calculated adsorption energies for heavy metal removal could be associated with physisorption-type forces. Finally, the adsorption mechanism analysis was complemented with the determination of adsorption thermodynamic functions using the statistical physics.

Adsorption of amoxicillin onto high surface area-activated carbons based on olive biomass: kinetic and equilibrium studies.

This study presents the extraction of antibiotic amoxicillin (AMX) from aqueous solution employing activated carbons (AC) from olive biomass (OB). Two AC were prepared using ZnCl2 (activator agent), and a conventional muffle furnace (ACF) or microwave oven (ACMW). The structure, morphology, and textural properties from both AC were analyzed by scanning electron microscope (SEM), pH of point-zero-charge (pHPZC), infrared spectroscopy (FTIR), and N2 adsorption/desorption isotherms. AC with mesoporous structures rich in oxygenated groups and high specific area (as high as 1742 m2 g-1) were helpful for the efficient and fast adsorption of AMX. The Avrami kinetic nonlinear equation showed the best fitting for the empirical data when related to the pseudo-1st and pseudo-2nd order. The isothermal experimental data followed the Liu nonlinear model, displaying at 25 °C the maximum sorption capacity of 237.02 and 166.96 mg g-1 for the ACF and ACMW, respectively. An adsorption test with synthetic hospital effluent was carried out to evaluate the possibility of applying both adsorbents in wastewater purification. The purification efficiency was up to 94.4% and 91.96% for ACF and ACMW, respectively. Therefore, the AC obtained from OB (containing a mixture of seed, pulp, and olive peel) has a high potential for application in removing emerging contaminants from the wastewater.

Utilization of Pacara Earpod tree (Enterolobium contortisilquum) and Ironwood (Caesalpinia leiostachya) seeds as low-cost biosorbents for removal of basic fuchsin.

Wastes from the Pacara Earpod tree (Enterolobium contortisilquum) and Ironwood (Caesalpinia leiostachya) seeds were studied as biosorbents for the removal of basic fuchsin from waters. Both biosorbents were prepared and characterized by different analytical methods. The characterization data showed that both materials were mainly composed of lignin, cellulose, and hemicellulose. Both biosorbents exhibited roughened surfaces and surface functional groups such as C-H, C=O, C=C, C-O, C-N, and OH bonds. Furthermore, the XRD pattern shows an amorphous phase with a wide peak from 10 to 30° due to the lignin. In terms of dosage and pH, the use of 1 g L-1 and 9.0, respectively, is recommended. The initial concentrations for the biosorption kinetics ranged from 50 to 500 mg L-1, where the Pacara ear and the Ironwood reached an adsorption capacity of 145.62 and 100.743 mg g-1 for the 500 mg L-1. The pseudo-second-order was found to be the proper model for describing biosorption of basic fuchsin onto Pacara Earpod tree and Ironwood, respectively. For the isotherm experiments, the maximum experimental biosorption capacity was found to be 166.858 and 110.317 mg g-1 for the Pacara Earpod and Ironwood for the initial concentration of 500 mg L-1 at 328 K. The Langmuir and the Tóth models were the best for representing the equilibrium curves for the basic fuchsin on the Pacara Earpod and the Ironwood, respectively. Maximum adsorption capacities of 177.084 mg g-1 and 136.526 mg g-1 were achieved for the Pacara Earpod tree and Ironwood, respectively. The biosorption process was spontaneous, endothermic, and favorable for both biosorbents. The biosorbents were also applied for coloration removal of simulated textile effluents, reaching 66% and 54% for the Pacara Earpod and Ironwood, respectively. For the final application, the materials were used in fixed-bed biosorption, with an initial concentration of 200 mg L-1, reaching breakthrough times of 710 and 415 min, leading to biosorption capacities of the column of 124.5 and 76.5 mg g-1, for the Pacara Earpod and Ironwood, respectively.

Functionalization of corn stover with 3-aminopropyltrietoxysilane to uptake Reactive Red 141 from aqueous solutions.

An alternative and low-cost adsorbent (CS-APTES) was developed by the functionalization corn stover (CS) with 3-aminopropyltrietoxysilane (APTES) using a simple method. Several analytical techniques were used to prove the functionalization and then, CS-APTES was employed to adsorb Reactive Red 141 (RR141) dye from aqueous solutions. The functionalization with APTES caused an increase of 15 times in the adsorption capacity. The adsorption of RR141 on CS-APTES was favored at pH 3.0 using a dosage of 3.0 g L-1. The adsorption equilibrium was reached within 4 h, being the process thermodynamically favorable, endothermic, and controlled by chemisorption. The maximum adsorption capacity was 15.65 mg g-1. CS-APTES was efficient to treat a colored effluent containing various ions and molecules. The use of 10 g L-1 of CS-APTES was sufficient to decolorize more than 98% of this effluent. It was concluded that CS-APTES can be easily prepared from CS, generating an efficient and low-cost adsorbent which, in turn, is able to treat colored effluents.

Kinetic, equilibrium, and thermodynamic studies on the adsorption of ciprofloxacin by activated carbon produced from Jerivá (Syagrus romanzoffiana).

High specific surface area activated carbon prepared from endocarp of Jerivá (Syagrus romanzoffiana) (ACJ) was used for ciprofloxacin (CIP) antibiotic removal from aqueous effluents. The activated carbon (AC) was characterized via scanning electron microscope, Fourier transform infrared spectroscopy, N2 adsorption/desorption, and pH value at the zero-charge point. Avrami kinetic model was the one that best fit the experimental results in comparison to the pseudo-first-order and pseudo-second-order kinetic models. The equilibrium data obeyed the Liu isotherm equation, showing a maximum adsorption capacity of 335.8 mg g-1 at 40 °C. The calculated thermodynamic parameters indicate that the adsorption of CIP was spontaneous and endothermic at all studied temperatures. Also, the free enthalpy changes (∆H° = 3.34 kJ mol-1) suggested physical adsorption between CIP and ACJ. Simulated effluents were utilized to check the potential of the ACJ for wastewater purification. The highly efficient features enable the activated carbon prepared from endocarp of Jerivá, an attractive carbon adsorbent, to remove ciprofloxacin from wastewaters.

Improvement of activated carbon characteristics by sonication and its application for pharmaceutical contaminant adsorption.

Sonicated activated carbon (SAC) was developed and used to remove ibuprofen and ketoprofen from aqueous media by adsorption. A standard activated carbon sample (AC) was used as comparison. Both adsorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption isotherms (Brunauer, Emmett, and Teller (BET)), helium gas pycnometry, and scanning electron microscopy (SEM). In the adsorption study, kinetics, equilibrium, and thermodynamics were evaluated. SAC presented better characteristics than AC. Pseudo-second-order model was adequate to predict the kinetic curves. The isotherm data obeyed the Sips model. Thermodynamic results revealed a spontaneous and endothermic process, where physisorption was involved. The maximum adsorption capacities of SAC were 134.5 and 89.2 mg g-1 for ibuprofen and ketoprofen, respectively. For AC, the maximum adsorption capacities were 115.1 and 79.1 mg g-1 for ibuprofen and ketoprofen, respectively. The sonication technique presented great potential to improve the AC characteristics, generating a promising material (SAC) for ibuprofen and ketoprofen adsorption.

Use of statistical design of experiments to evaluate the sorption capacity of 7-amine-4-azaheptylsilica and 10-amine- 4-azadecylsilica for Cu(II), Pb(II), and Fe(III) adsorption.

7-Amine-4-azaheptylsilica (AAH Si) and 10-amine-4-azadecylsilica (AAD Si) were prepared and used for removal of Cu(II), Pb(II), and Fe(III) from aqueous solutions. Full 2(3) factorial designs with two pseudo-central points were carried out in order to achieve the best conditions of the batch adsorption procedure for metallic ion uptake by the adsorbents. To continue the optimizations, central composite surface design was also employed. These two independent statistical designs of experiments lead to the following conditions: m=30.0 mg of adsorbent; pH 6.0 for Cu(II) and Pb(II), pH 4.0 for Fe(III); t of contact 180 min to guarantee equilibration at higher adsorbate concentration. After optimization of the conditions, isotherms of the metallic ions adsorbed on the AAH Si and AAD Si adsorbents were obtained, which were fitted to nonlinear Langmuir and Freundlich isotherm models.

Cellulose microfiber functionalized with N,N'-bis (2-aminoethyl)-1,2-ethanediamine as a solid sorbent for the fast preconcentration of Cd(II) in flow system analysis.

The present paper describes the synthesis of a new chemically modified cellulose microfiber through oxidation with sodium periodate and functionalization with N,N'-bis (2-aminoethyl)-1,2-ethanediamine for the fast and selective preconcentration of Cd(II) ions in flow system analysis. The new sorbent was characterized by FTIR, SEM, and surface area values. The uptake behavior of Cd(II) ions onto this sorbent was evaluated from kinetic data, pseudo-first-order and pseudo-second-order models, as well as from Langmuir, Freundlich and Langmuir-Freundlich adsorption isotherms. The maximum sorption capacity of 4.59 mg g(-1) was estimated by the Langmuir-Freundlich model with fast kinetics for the sorption of Cd(II) described by the pseudo-second-order kinetic model. After characterization, the sorbent was packed in a mini-column, and a fast flow injection preconcentration system for Cd(II) determination by FAAS was developed. The best Cd(II) preconcentration condition, obtained by means of factorial design and response surface methodology, was achieved at pH 9.36 and a flow rate of 10 mL min(-1) followed by elution with 1.0 mol L(-1) nitric acid. By using 78 s preconcentration time, fast and highly sensitive determination of Cd(II) ions could be achieved with a limit of quantification of 0.20 µg L(-1), preconcentration factor of 26, consumption index of 0.5 mL, concentration efficiency of 20 min(-1), and sample throughput of 39 h(-1). The repeatability for 10 replicate determinations was found to be 7.8 and 2.5% for Cd(II) ion concentrations of 5.0 and 100.0 µg L(-1), respectively. The new sorbent efficiency for the interference-free preconcentration of Cd(II) ions was assessed by analysis of tap, mineral and lake waters, as well as synthetic seawater and normal saline waters. Furthermore, complex samples, such as biological samples, could be analysed by the proposed method in accordance with the accuracy attested by analysis of certified reference materials, TORT-2 (lobster hepatopancreas), and DOLT-4 (dogfish liver).