Boehm Titration Research Articles

Improved carboxylate density hydrochar by alkylation of surface phenol for adsorption of cationic dye in aqueous solution

Methylene blue (MB) adsorption in aqueous solution studied using rice straw derived hydrochar (RSH) and carboxylate functionalized hydrochar (RSHC) as adsorbent. RSHC with improved carboxylate functional group density was prepared by selective functionalization of phenolic oxygen functional groups present on RSH surface. The RSH and RSHC were characterized by ultimate and proximate analysis, Boehm Titration, 13C CP-MAS SS NMR, XPS, SEM, BET surface area and zeta potential analysis. Batch adsorption experiments were optimized for MB adsorption were, adsorbent dose of 0.2 g/L, pH 8 and 7, respectively for RSH and RSHC, with 3.5 h contact time at 298 K. Nonlinear fit to Langmuir, Freundlich, Temkin, d-R models and Sips isotherm models, showed good fit with R2>0.95. RSHC (Qm = 434.6 mg/g) showed four-fold increase in MB adsorption as compared to the pristine hydrochar RSH (Qm =111.6 mg/g). Contact time study showed good nonlinear fit to pseudosecond order model indicating a strong interaction between hydrochar adsorbents and MB. Thermodynamics of MB adsorption (288–308 K) onto the surface of RSH and RSHC, is a spontaneous process with ∆G° -23.85 and -28.31 kJ/mol, respectively. RSH in characterized by enthalpy driven adsorption characteristic of proton-MB exchange, whereas in case of RSHC, K+–MB exchange is entropically driven process.

Effects of pyrolysis temperatures on the structural properties of straw biochar and its adsorption of tris-(1-chloro-2-propyl) phosphate

To investigate the effect of pyrolysis temperature on the adsorption behavior of the emerging organic pollutant tris-(1-chloro-2-propyl) phosphate (TCIPP) on biochar, corn stover was used as raw materials to prepare biochars at different pyrolysis temperatures (250, 350, 500, 700 °C) through limited oxygen carbonization. Elemental analysis, Boehm titration, FTIR, XPS, and other analytical methods were used to reveal the effect of pyrolysis temperature on the physicochemical properties of biochar and its mechanism of TCIPP adsorption. The results showed that the pyrolysis temperature had a significant impact on the physicochemical properties of biochar. As the pyrolysis temperature increases, the specific surface area of biochar rises from 3.083 m2/g to 435.573 m2/g, the pH value increases from 6.60 to 10.66, the mass percentage of C increases from 63.10 to 80.58%, and the mass percentage of O decreases from 26.42 to 9.20%. Additionally, the hydrophobicity and aromaticity of biochar also increase with rising pyrolysis temperature, while its polarity decreases. Boehm titration, FTIR, and XPS analysis showed that the total amount of functional groups on the surface of biochar decreased relatively with increasing temperature. Functional groups such as -OH, C = C/C = O, and C-O-C participated in the adsorption of TCIPP on biochar, and ester groups were produced after adsorption. The adsorption process of TCIPP on biochar fits best with the pseudo-second-order equation, indicating that the adsorption process is mainly chemical adsorption, and the main rate-controlling stage is intraparticle diffusion. The isothermal adsorption results were more in line with the Temkin model, indicating that the adsorption process of TCIPP on biochar was mainly surface adsorption. As the pyrolysis temperature increases, the maximum adsorption capacity of biochar increases from 0.8837 mg/g to 2.2574 mg/g. The adsorption process of TCIPP on biochar mainly included pore filling, hydrogen bonding, P-π interaction, hydrophobic interaction, and electrostatic attraction. Among them, pore filling, P-π interaction, and hydrophobic interaction were significantly enhanced with increasing temperature, while hydrogen bonding was relatively weakened. This study will provide a theoretical basis and technical support for the removal of TCIPP from water using biochar adsorption.

Cnicus Benedictus roots as a low-cost adsorbent for methylene blue dye removal from aqueous solution: kinetic and equilibrium studies

In this research, Cnicus Benedictus roots powder (CBRP) was utilized as a low-cost adsorbent for removing methylene blue (MB) as a cationic dye from aqueous solution. Characterization of CBRP by Boehm titration method, Fourier transform infrared (FT-IR) and environmental scanning electron microscope (ESEM) indicates the presence of different types of functional groups and a very rough surface filled with cavities, suitable for MB adsorption. The effect of various parameters such as CBRP dose (0.2–2 g/1L), contact time (0–180 min), initial pH (1–10), coexisting anions/cations and the initial MB concentration (100–500 mg L−1) on MB adsorption were examined, the results showed that MB uptake depends on the pH of solution, the electrostatic attraction forces, the formation of H-bonds and π–π interactions are the possible CBRP–MB interaction mechanisms. Adsorption kinetic of MB on CBRP was best represented by linear and non-linear form of the pseudo-second order model. The experimental equilibrium data were best described by linear and non-linear forms of Langmuir and Redlich–Peterson isotherm models (R 2> 0.98) with a maximum MB adsorption capacity of 85.47 mg g−1 at 25 °C, the adsorption efficiency R (%) was greater than 90 (%). MB adsorption-desorption experiments showed the reusability of CBRP for five consecutive cycles. According to the obtained results, CBRP can be used as a natural adsorbent material for cationic dyes removal from aqueous solution.

Research over the effect of activated carbon treated with calcium nitrate solution on the catalytic ability in the reduction of Co(III)Triethylenetetramine

AbstractActivated carbon can be used as a catalyst for the reduction of Co(III)TETA to Co(II)TETA so as to maintain the ability of removing NO from gas stream with Co(II)TETA solution. Calcium nitrate has been utilized to treat activated carbon to improve its catalytic ability in the regeneration of Co(II)TETA. The biggest Co(III)TETA conversion is gained by the carbon being soaked in 0.3 mol/L calcium nitrate solution at 65°C for 12 h with a solid/liquid ratio of 1 g/50 mL followed being carbonized at 400°C for 2 h in nitrogen. The characterization with Fourier transform infrared spectroscopy, XPS, BET (Brunauer‐Emmett‐Teller) and Boehm titration indicates that the modification with calcium nitrate increases the specific surface area and acidic groups on activated carbon. The continuous experiments reveal that the NO removal efficiency obtained by the modified carbon is over 12% up to that by the original one.

Reduction of 2,4-dichlorophenoxy acetic acid herbicide toxicity from aqueous media by adsorption: Experimental and theoretical study using DFT method

This work studies the possibility of reducing the toxicity of water laden with 2,4-dichlorophenoxy acetic acid (2,4-D) using a commercial activated carbon (AC). Multiple structural and textural characterization techniques including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM/EDS), point of zero charge (pHzpc) determination, Boehm titration, iodine number, Methylene blue index, and BET analysis measurements were performed on the commercial AC. Various parameters affecting adsorption were studied and well-known isotherms models in their linear and non-linear forms were applied for fitting equilibrium data. The kinetic data was analyzed using intraparticle diffusion, pseudo-first and second-order kinetic models. Density functional modeling (DFT) of 2,4-dichlorophenoxyacetic acid was used to investigate the origin of the reactivity. The AC surface area was found to be 1017 m2⋅g−1. A contact time of 30 min, an AC dose of 4 g⋅L−1 and a pH of 6.2 resulted in a maximum adsorption capacity of 235.55 ± 6.43 mg⋅g−1. The thermodynamic study revealed that the adsorption process was physical, spontaneous and endothermic. The adsorption process was governed by second-order kinetics and controlled by intraparticle diffusion.

Adsorptive separation of anthracene and carbazole by carboxyl-functionalized carbon material derived from MAF-6

Anthracene and carbazole are high-value heavy carbon resources mainly found in the anthracene oil fraction of high-temperature coal tar. Because of their similar structures, traditional solvent crystallization methods are not capable of achieving the separation of high-purity anthracene and carbazole. In this study, MAF-6, a material that can be synthesized in large quantities at room temperature, was used as a sacrificial precursor, carbonized (MC-1000), and subsequently oxidized to form carboxyl-functionalized carbon material (CMC-1000). The presence of carboxyl groups, along with lactones, hydroxyl groups, and carbonyl groups in MC-1000 and CMC-1000, was confirmed through XPS spectra and Boehm titration. CMC-1000 showed an increase of 5.7 mmol/g in oxygen-containing functional groups. The adsorption and separation capacities of MAF-6, MC-1000, and CMC-1000 for anthracene and carbazole in model oil were investigated. FT-IR analysis and DFT calculations demonstrated that the major interaction between CMC-1000 and carbazole involved hydrogen bonding (N–H···O and N–H···N). The results show that CMC-1000 has a high separation selectivity for carbazole over anthracene, with a selectivity of up to 44.4. The formation of hydrogen bonds between the N–H group of carbazole and the oxygen-containing groups on CMC-1000 plays an essential role in achieving high adsorption capacity and selectivity. In addition, CMC-1000 showed strong regenerative capacity, maintaining a selectivity above 29.7 over five cycles.

Assessment of the Nutritional Benefits and Aflatoxin B1 Adsorption Properties of Blackberry Seed Cold-Pressed Oil By-Product.

This study explores the potential valorization of blackberry seed oil cake (BBSOC), a by-product of cold-pressed blackberry seed oil (Rubus fruticosus L.), as a nutritionally valuable material with aflatoxin B1 (AFB1) adsorption properties. The chemical and mineral composition, polyphenols, and antioxidant activity of BBSOC flour were assessed. BBSOC was found to be a significant source of fiber (62.09% dry weight) and essential minerals such as Fe (123.48 mg/kg), Mg (1281.40 mg/kg), K (3087.61 mg/kg), and Ca (1568.41 mg/kg). The high polyphenol content, especially ellagic acid, highlighted its biologically active potential. Moreover, BBSOC demonstrated effective biosorption of AFB1 under in vitro conditions at 37 °C, with adsorption efficiencies of 85.36% and 87.01% at pH 3 and 7, respectively. Characterization techniques including SEM, FTIR analysis, Boehm titration, and pH zero charge determination confirmed its AFB1 adsorbing properties. This valorization process reintroduces a secondary product into the food chain, supporting the circular economy and zero-waste concepts. Thus, BBSOC is nutritionally rich and effective in AFB1 biosorption, presenting potential applications as a food or feed additive.

Key Control Characteristics of Carbon Black Materials for Fuel Cells and Batteries for a Standardized Characterization of Surface Properties

AbstractCarbon Blacks (CBs) are primarily used in electrocatalysis as support materials for nanoparticulate electrocatalysts. In fuel cells, CBs, catalysts, and proton conductive polymers (ionomers) undergo a dispersion/homogenization process for electrode coating. The interactions between components in dispersion and the surface of CB particles are complex. The surface characteristics of CB particles impact slurry formulation, electrode coating, and the resulting electrode layer, affecting fuel cell and battery performance and durability. This study investigates commercially available CBs such as Vulcan XC72R, Ketjen Black EC‐300J, Ketjen Black EC‐600JD, and Super C65, focusing on application‐relevant key control characteristics (KCCs). The KCCs include physicochemical features like electrical conductivity (electron transport through the catalyst layer, CL), oxygen‐containing surface groups (hydrophilicity/phobicity of the CL, catalyst functionalization), surface basicity/acidity, ionomer adsorption, and particle dispersibility (catalyst ink stability). KCCs are determined by particle bulk electrical conductivity, Boehm titration (BT), isoelectric point (IEP), and Hansen solubility parameters (HSP). HSP, understood as similarity parameters for particles, indicate how nanoparticle surfaces interact with liquids during dispersion. The proposed KCCs serve as a starting point for characterizing CBs and guiding product design to obtain meaningful structure‐property relationships, essential for a successful energy transition.

One-pot amination and carboxylation functionalization of lignin for efficient adsorption of Cr(VI) and Cd(II): Influence of functional groups on adsorption equilibrium and mechanism

The removal of multiple heavy metal pollutants remains a challenge. Amination and carboxylation modified lignins (NCLs) prepared by one-pot hydrothermal method were used as adsorbents for Cr(VI) and Cd(II) removal. The oxygenous groups content in adsorbents was quantitatively analyzed by Boehm titration in which NCL10 (the mass ratio of citric acid: triethylene diamine = 10) possessed a maximum carboxyl group content of 1.22 mmol/g. The Langmuir adsorption isotherm model was the most suitable, with the highest theoretical adsorption capacity of Cr(VI) and Cd(II) of 1298.6 and 103.1 mg/g, respectively. Meanwhile, FT-IR and XPS exhibited that NCL5 surface contained many functional groups beneficial to the removal of Cr(VI) and Cd(II). The contribution of carboxyl and hydroxyl groups to the removal of Cr(VI) and Cd(II) was quantitatively analyzed. After the blocking of carboxyl and hydroxyl groups, the adsorption rate of Cr(VI) and Cd(II) decreased by 26.4 %, 67.7 % and 7.2 %, 43.3 %, respectively. This study provides effective strategies to overcome the limitations of lignin adsorbents for wastewaters containing a wide range of heavy metal pollutants.

Methylene Blue and Rhodamine B Dyes' Efficient Removal Using Biocarbons Developed from Waste.

The preparation of biocarbons from cellulose fibres utilised in the production of baby nappy mats (sourced from Feniks Recycling company, Poland) for the removal of methylene blue and rhodamine B dyes has been documented. A Brunauer, Emmett and Teller analysis revealed a surface area within the range of 384 to 450 m2/g. The objective of this study was to investigate the removal efficiency of dyes from aqueous solutions by biocarbons, with a particular focus on the influence of various parameters, including pH, dye concentration, adsorbent dosage, shaking speed, contact time, and temperature. The maximum adsorption capacity of the dyes onto the biocarbons was found to be 85 mg/g for methylene blue and 48 mg/g for rhodamine B, respectively. The Langmuir equation proved to be the most suitable for interpreting the sorption of organic dyes. The adsorption process was found to exhibit a chemisorption mechanism, effectively mirroring the pseudo-second-order kinetics. Furthermore, the adsorption of dyes was observed to be endothermic (the enthalpy change was positive, 9.1-62.6 kJ/mol) and spontaneous under the tested operating conditions. The findings of this study indicate that biocarbons represent a cost-effective option for the removal of methylene blue and rhodamine B. The adsorption method was observed to be an effective and straightforward approach for the removal of these dyes. The results of the Boehm titration analysis and zero charge point value indicated that the synthesised biomaterials exhibited a slightly basic surface character.

Influence of Tectonically Deformed Coal-Based Activated Carbon and Its Surface Modification on Methane Adsorption.

A series of coal-based activated carbons (CACs) were synthesized from mylonitized fat coal, a type of tectonically deformed coal (TDC) and symbiotic primary structural coal (PSC), followed by oxidative modification. The pore structure, surface oxygen-containing functional groups, and their influence on methane adsorption by CAC as the simplified coal model were investigated by using low-temperature nitrogen adsorption, Fourier transform infrared spectroscopy, Boehm titration, and X-ray photoelectron spectroscopy. The results showed that tectonic deformation fostered smaller pores, particularly ultramicropores in TDC, dominating methane adsorption. Acid-modified TDC-based activated carbons (ACs) showed higher pore parameters and oxygen-containing functional groups than those of PSC-based ACs. Nitric acid introduced abundant carboxyl groups concurrently increasing the pore volume and specific surface area (SSA), while sulfuric acid-ammonium persulfate treatment resulted in increased lactone groups and a partial collapse/blockage of nanopores. Methane adsorption experiments confirmed the importance of micropores and revealed a significant decrease in capacity owing to increased oxygen-containing functional groups as the primary role, with pore wall corrosion playing a secondary role. Thus, the study highlights the surface effects of TDC on methane adsorption and the potential for producing high-performance methane storage materials from China's tectonic coal resources.

Production of activated carbons from Quercus cerris acorn shell under various experiment conditions, and their characterizations

Due to the high porosities, large surface areas, insolubilities in solutions, and unique structural and morphological structures, porous materials are utilized in various application areas such as energy conversion and storage, wastewater treatment, adsorption, catalysis and photocatalysis. In this study, activated carbons (QCACs), one type of porous materials, were synthesized from Quercus cerris acorn shells by using ZnCl2 chemical activation under various production conditions. The effects of carbonization temperature, carbonization period, and impregnation ratios on the yields, surface areas, pore developments, and N2 adsorption–desorption isotherms of activated carbons obtained were investigated in detail. The highest surface area (1751.61 m2/g) was reached when utilized at the impregnation ratio of 2.0 at 500 ℃ for 90 min. The total pore volume of QCAC increased with increasing impregnation ratio, however the micropore volume of QCAC reduced. It was found from the pore distribution data that QCACs contained mostly narrow mesopores and a little amount of micropores. Also, N2 adsorption–desorption isotherm data revealed that QCACs produced under different conditions were usually mesopore structures, and the pores were narrow slit-shaped. Moreover, the data provided from SEM, FTIR, Boehm titration, and elemental analysis gave more characterization information about QCACs synthesized.

Synthesis and application of biochar from agricultural by-products. Effect of pyrolysis temperature on the acid-base properties of biochar

Biochar was synthesized from banana peels using the pyrolysis method in a nitrogen gas environment. The pyrolysis temperature ranged from 100°C to 500°C with a heating rate of 5°C per minute and a pyrolysis time of 1.5 hours. The influence of the pyrolysis temperature on the acid-base properties of the biochar surface was evaluated through characteristic SEM and BET measurements. Boehm titration showed a gradual decrease in the total acid functional groups and an increase in the total base functional groups with the increasing pyrolysis temperature. Methylene Blue (MB) was used as a model substance to investigate the adsorption properties of the synthesized biochar. The Langmuir and Freundlich models were employed to describe the adsorption equilibrium. The kinetics of MB adsorption followed a pseudo-second-order kinetic equation. The adsorption capacity of MB by biological charcoal was influenced by the acid-base properties of the material, indicating the impact of the pyrolysis temperature.

A green method to improve adsorption capacity of hydrochar by ball-milling: enhanced norfloxacin adsorption performance and mechanistic insight

The application of hydrochar as a cost-effective solution has received much attention for the remediation of contaminated water. An economical and environmental approach to enhancing the physicochemical and adsorption performance of hydrochar is essential. In this study, the green technology of ball-milling was firstly employed to improve the adsorption capacity of hydrochar for the typical antibiotics norfloxacin. Aqueous batch adsorption experiment using both pristine and ball milled hydrochar derived from water hyacinth, prepared by hydrothermal carbonization at three temperatures (180, 200, 220 °C) was conducted. The results showed that ball-milling decreased the specific surface area of hydrochar, but still greatly enhanced their performance on the adsorption of norfloxacin. Surface functional groups, aromatization degree, and hydrophobicity of hydrochar were increased after ball-milling, as evidenced by measurements of Boehm titration, Raman spectra, and contact angle, respectively. With these changes, all the ball-milled water hyacinth hydrochar exhibited a better performance on the adsorption of norfloxacin than pristine hydrochar. Ball-milled 220 °C water hyacinth hydrochar showed the greatest norfloxacin adsorption (68.53 mg g−1) compared to unmilled hydrochar (24.29 mg g−1), and the enhancement was effective in a wide pH range (5–9) in aqueous solutions. The thermodynamics study indicated that the norfloxacin adsorption on ball-milled hydrochar was both physically spontaneous and exothermic. Combined physicochemical characterization of hydrochar and batch experiment results suggest that the enhanced adsorption capacity was owing to boosting H-bonds, π-π electron-donor–acceptor, and hydrophobic interaction. This study suggested that ball-milling can be served as a facile, green, and cost-effective method to obtain modified hydrochar for the removal of pollutants in water.

STUDY ON THE CO\(_2\) ADSORPTION PROPERTIES OF ACTIVATED CARBON PRODUCED FROM CORN COB

Activated carbon (AC) prepared from corn cobs was used as an adsorbent for CO2 capture under different temperatures. The characterization by Boehm titration and TGA showed that the total acidic groups of AC were significantly higher than the total basic groups, and the increasing activated temperature resulted in increases in the total basicity and decreases in the total acidity. The CO2 adsorption behavior of AC was predicted by four isotherm models. It was found that the suitable order was Sips > Tóth > Freudlich > Langmuir. The maximum monolayer coverage capacity and isosteric heat of adsorption were in the range of 6.28 - 10.92 mmol g-1 and 26.48 - 21.55 kJ mol-1, respectively. High specific surface area and high amount of carboxylic groups were found to be in favor of CO2 capture.

Synthesis and Characterization of Porous Materials from Waste Wheat Bran

The purpose of this study was to investigate how the amount of ZnCl2 and temperature affect the process of converting waste wheat bran, known for its hemicellulose struc-ture, into porous material. The characterization of the wheat bran was done using proximate and primary component analysis, and Thermogravimetric analysis (TG) test, Fourier Transform Infrared Spectroscopy (FT-IR) spectra, Energy-dispersive X-ray spectroscopy (EDS) results, and Scanning electron microscopy (SEM) images. The influence of temperature on the surface areas of activated carbons is more significant than the impact of varying the amount of ZnCl2. When the carbonization temperature reached 500 °C, porous structures developed, and the highest surface areas achieved for all impregnation ratios (1:1, 2:1, and 3:1) were 1234, 1478, and 1422 m2/g, respectively. Activated carbon was found to have acidic (0.88 mmol/g) and basic (0.54 mmol/g) functional groups on its surface, after being synthesized through carbonization at 500 °C using ZnCl2 at a 2:1 impregnation ratio in accordance with Boehm titration. This promising activared carbon made from wheat bran, activated by ZnCl2, is efficient and environmentally friendly, and it is a potential solution for water pollution treatment.

Efficient Removal of Nickel from Wastewater Using Copper Sulfate-Ammonia Complex Modified Activated Carbon: Adsorption Performance and Mechanism.

The necessity to eliminate nickel (Ni) from wastewater stems from its environmental and health hazards. To enhance the Ni adsorption capacity, this research applied a copper sulfate-ammonia complex (tetraamminecopper (II) sulfate monohydrate, [Cu(NH3)4]SO4·H2O) as a modifying agent for a Phragmites australis-based activated carbon preparation. The physiochemical properties of powdered activated carbon (PAC) and a modified form ([Cu(NH3)4]-PAC) were examined by measuring their surface areas, analyzing their elemental composition, and using Boehm's titration method. Batch experiments were conducted to investigate the impact of various factors, such as Ni(II) concentration, contact time, pH, and ionic strength, on its substance adsorption capabilities. Additionally, the adsorption mechanisms of Ni(II) onto activated carbon were elucidated via Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The findings indicated that modified activated carbon ([Cu(NH3)4]-PAC) exhibited a lower surface area and total volume than the original activated carbon (PAC). The modification of PAC enhanced its surface's relative oxygen and nitrogen content, indicating the incorporation of functional groups containing these elements. Furthermore, the modified activated carbon, [Cu(NH3)4]-PAC, exhibited superior adsorption capacity relative to unmodified PAC. Both adsorbents' adsorption behaviors conformed to the Langmuir model and the pseudo-second-order kinetics model. The Ni(II) removal efficiency of PAC and [Cu(NH3)4]-PAC diminished progressively with rising ionic strength. Modified activated carbon [Cu(NH3)4]-PAC demonstrated notable pH buffering and adaptability. The adsorption mechanism for Ni(II) on activated carbon involves surface complexation, cation exchange, and electrostatic interaction. This research presents a cost-efficient preparation technique for preparing activated carbon with enhanced Ni(II) removal capabilities from wastewater and elucidates its underlying adsorption mechanisms.

Unary adsorption of sulfonamide antibiotics onto pozzolan-tyre ash based geopolymers: Isotherms, kinetics and mechanisms

In this contribution, geopolymer composites, GP0, GP5-TA and GP10-TA, were prepared by alkaline activation and substituting pozzolan (Pz) with 0, 5 and 10 wt% of tyre ash (TA), respectively. The geopolymers were characterized using standard methods (XRD, TGA, FTIR, BET, SEM, Boehm titration and methylene blue and iodine indices) and were applied for the abatement of two sulfonamides, sulfamethoxazole (SMX) and sulfadimethoxine (SDM) in single-solute solutions. The effects of pH, salinity, initial concentration and contact time were evaluated. The incorporation of 5 and 10% TA increased the specific surface area (SSA) of pristine geopolymer (GP0) from 13.62 to 21.48 and 29.70 m2.g−1, respectively. The equilibrium data was best described by the Sips isotherm model. Salinity significantly diminished the adsorption of SMX and SDM. In aqueous medium, the geopolymers exhibited higher adsorption capacity for SDM (log Kow, 1.17) relative to SMX (log Kow, 0.86). In contrast, in saline medium, SMX uptake was higher, suggesting a cation-mediated adsorption. Adsorption of SMX was uncharacteristically independent of pH, whereas SDM uptake was significantly pH-dependent. The GP5-TA geopolymer composite exhibited the highest adsorption capacity for SMX in a saline environment (46.69 mg.g−1) and for SDM in non-saline water (107.69 mg.g−1). Adsorption rate was described by the pseudo-second order kinetic law. Adsorption mechanism was multi-mechanistic involving hydrophobic, ion exchange and charge assisted hydrogen bonding and electrostatic interactions in the case of SDM. Future works should optimize the functional groups density of active sites especially for sulfonamides in saline waters.

Application of chemically modified waste tucumã (Astrocaryum aculeatum) seeds in the biosorption of methylene blue: kinetic and thermodynamic parameters.

Dye effluents cause diverse environmental problems. Methylene blue (MB) dye stands out since it is widely used in the textile industry. To reduce the pollution caused by the MB, we developed biosorbents from tucumã seeds, where the in natura seeds were treated with NaOH (BT) and H3PO4 (AT) solutions and characterized by Boehm titration, point of zero charges, FTIR, TGA, BET, and SEM. It was observed that the acid groups predominate on the surface of the three biosorbents. The process was optimized for all biosorbents at pH = 8, 7.5g/L, 240min, C0 = 250mg/L, and 45 ℃. BT was more efficient in removing MB (96.20%; QMax = 35.71mg/g), while IT and AT removed around 60% in similar conditions. The adsorption process best fits Langmuir and Redlich-Peterson isotherms, indicating a hybrid adsorption process (monolayer and multilayer) and pseudo-second-order kinetics. Thermodynamic data confirmed an endothermic and spontaneous adsorption process, mainly for BT. MB was also recovered through a desorption process with ethanol, allowing the BT recycling and reapplication of the dye. Thus, an efficient and sustainable biosorbent was developed, contributing to reducing environmental impacts.

Synthesis of Cr(VI)-adsorbed carbon from Artocarpus heterophyllus peel waste: activated conditions, characterizations and adsorption isotherm

Lignocellulosic biomass is often activated with phosphoric acid to make value-added goods. However, statistical effects of impregnation ratio (IR) and activation temperature (AT) on Artocarpus heterophyllus peel-derived activated carbon have not been studied. This study used an experimental approach and regression model to investigate these impacts on Cr(VI) adsorption capacity. A regression model and analysis of variance assessed these two factors’ variation. The activated carbon’s morphology, surface functional groups, and Cr(VI) adsorption isotherm at optimal conditions were examined using Brunauer, Emmett and Teller, X-ray diffraction, Scanning Electron Microscopy, Fourier Transform Infrared Spectrometry, Boehm titration, pH drift methods, Langmuir, and Freundlich models. The quadratic regression model described the influence of AT and IR on Cr(VI) adsorption capacity and found the best values of 545°C and 4:1. When IR and AT ranged from 1.89 to 4.0 and 330°C to 545°C respectively, the combined effect caused the most variance and had a synergistic effect on Cr(VI) adsorption capacity. This activated carbon at optimal conditions had many carboxylic groups, a porous, amorphous surface, and a maximum mono-layer capacity of 29.498 mg g-1. Freundlich is a better Cr(VI) adsorption model. This study will give a technical way and advocate for the utilization of activated carbon derived from Artocarpus heterophyllus peel as an effective material for the removal of chromium (VI) from water.