Basic dye adsorption onto an agro-based waste material--sesame hull (Sesamum indicum L.)

Exploring adsorption capacity and mechanisms involved in cadmium removal from aqueous solutions by biochar derived from euhalophyte

Biochar has shown potential as a sorbent for reducing Cd levels in water. Euhalophytes, which thrive in saline-alkali soils containing high concentrations of metal ions and anions, present an intriguing opportunity for producing biochar with inherent metal adsorption properties. This study focused on biochar derived from the euhalophyte Salicornia europaea and aimed to investigate its Cd adsorption capacity through adsorption kinetics and isotherm experiments. The results demonstrated that S. europaea biochar exhibited a high specific surface area, substantial base cation content, and a low negative surface charge, making it a highly effective adsorbent for Cd. The adsorption data fit well with the Langmuir isotherm model, revealing a maximum adsorption capacity of 108.54 mg g-1 at 25 °C. The adsorption process involved both surface adsorption and intraparticle diffusion. The Cd adsorption mechanism on the biochar encompassed precipitation, ion exchange, functional group complexation, and cation-π interactions. Notably, the precipitation of Cd2+ with CO32- in the biochar played a dominant role, accounting for 73.7% of the overall removal mechanism. These findings underscore the potential of euhalophytes such as S. europaea as a promising solution for remediating Cd contamination in aquatic environments.

Adsorption and Degradation of Organics in Wastewater on Municipal Sludge

Adsorption and degradation of organic compounds on sludge were investigated by comparing activated and inactivated sludge at various dosages, pH values, and temperatures. The organic compounds in wastewater were identified and evaluated through fluorescence spectra. The results show that optimum adsorption occurred as the activated and inactivated sludge concentration was 4000 mg/L at a pH of 7.99 and a temperature of 30 °C. The fluorescence scanning spectrum indicated that activated sludge could remove protein-like organic matter, fulvic acid-like organic matter, and humic acid-like organic matter by 22.1, 9.4, and 41.2%, respectively, via adsorption only or by 25.9, 9.8, and 74.3%, respectively, via adsorption and degradation. Under optimum conditions, by using the good adsorption performance of sludge combined with other sewage treatment technologies, the treatment of high-content organic wastewater can be achieved.

Utilization of electron beam irradiated carboxymethyl cellulose/polyvinyl alcohol/banana peels composite film for remediation of dyes from wastewater

In this work, polymeric composite films were fabricated utilizing stable, non-toxic, soluble, low-cost, good mechanical, and biocompatible polymers such as CMC and PVA with the waste of one of the most current fruits consumed worldwide banana peel waste (BP) as a filler. Sequences of carboxymethyl cellulose/polyvinyl alcohol/banana peel (CMC/PVA/BP) composite films with various amounts of BP utilizing eco-friendly technique (electron beam) (EB) irradiation were prepared to eliminate common hazardous organic pollutants such as methylene blue (MB) dye from its solutions. Physical characteristics like; swelling and gel % were examined. The chemical structure, thermal stability, and surface morphology were examined utilizing FT-IR, TGA, DSC, XRD, EDX, and SEM. Additionally, the UV/Vis spectroscopy study was investigated to study the impact of the various parameters such as irradiation, contact time, pH, temperature, adsorbent dosage, and initial concentration on removal efficiency % of MB dye onto the prepared composite films. The adsorption process fitted with the Langmuir model, pseudo-second-order kinetic model, endothermic, favorable, and spontaneous. The adsorption capacity of MB dye onto the CMC/PVA/BP composite film was 19.6 mg/g at the optimum conditions: irradiation dose = 20 kGy, contact time = 120 min, pH = 10, temperature = 25 °C, adsorbent dosage = 0.1 g and initial conc. = 10 mg/L.

Propensity of a low-cost adsorbent derived from agricultural wastes to interact with cationic dyes in aqueous solutions

Ash collected from thrown-away by-products while preparing a popular traditional food additive, kolakhar of the Assamese community of North East, India, was used as an alternate cost-effective, porous bioadsorbent option from the conventional activated carbon for the purification of carcinogenic dyes laden water. The base material for kolakhar preparation was taken from the discarded banana stem waste to stimulate agricultural waste management. Methylene blue (MB) and basic fuchsin (BF) dyes were used as model cationic dyes. Characterization techniques like CHN, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission-scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), and Brunauer-Emmett-Teller (BET) analysis of the prepared banana stem ash (BSA) reveal the presence of high inorganic contents and functional groups in the irregular, porous bioadsorbent with surface area 55.534 m2 g-1. Various regulating parameters studied to optimize the adsorption capacity of BSA were bioadsorbent dose (0.1-3 g/L), temperature (298-318 K), contact time (0-150 min), pH (2-9), and initial dye concentrations (10-40 mg/L). Non-linear kinetic models suggested Elovich for both MB and BF adsorption, while the non-linear isotherm model suggested Langmuir and Temkin for MB and BF adsorption, respectively, as best-fitted curves. The monolayer adsorption capacity (qm) for MB and BF was 15.22 mg/g and 24.08 mg/g at 318 K, respectively, with more than 95% removal efficiency for both dyes. The thermodynamic parameters studied indicated that the adsorption is spontaneous. The ∆H0 values of MB and BF adsorptions were 2.303 kJ/mol (endothermic) and - 29.238 kJ/mol (exothermic), respectively.

Improved methylene blue adsorption from an aqueous medium by ozone-triethylenetetramine modification of sawdust-based biochar

In this study, sawdust biochar-O₃-TETA (SDBT), a novel biochar, was prepared via treatment with 80% sulfuric acid, followed by oxidation by ozone and subsequent treatment with boiling Triethylenetetramine (TETA). Characterization studies of the prepared SDBT adsorbent were performed with SEM-EDX, BET, XRD, BJH, FT-IR, DTA and TGA analyses. The adsorption efficiency of MB dye by SDBT biochar from water was investigated. Methylene Blue (MB) dye absorption was most effective when the solution pH was 12. The maximum removal % of MB dye was 99.75% using 20 mg/L as starting MB dye concentration and 2.0 g/L SDBT dose. The Q_m of the SDBT was 568.16 mg/g. Actual results were fitted to Temkin (TIM), Freundlich (FIM), and Langmuir (LIM) isotherm models. The experimental results for SDBT fitted well with all three models. Error function equations were used to test the results obtained from these isotherm models, which showed that the experimental results fit better with TIM and FIM. Kinetic data were investigated, and the pseudo-second-order (PSOM) had R² > 0.99 and was mainly responsible for guiding the absorption rate. The removal mechanism of the MB dye ions in a base medium (pH 12) may be achieved via physical interaction due to electrostatic interaction between the SDBT surface and the positive charge of the MB dye. The results show that SDBT effectively removes the MB dye from the aqueous environment and can be used continually without losing its absorption efficiency.

Three-dimensional lignin-based polyporous carbon@polypyrrole for efficient removal of reactive blue 19: A synergistic effect of the N and O groups

Reactive blue 19 is one of the abundant carcinogens commonly used in industrial applications. This study transformed industrial lignin into a lignin-based polyporous carbon@polypyrrole (LPC@PPy) by a hydrothermal-activation-in situ polymerization strategy for removal of reactive blue 19. The hydrothermal reaction and polypyrrole polymerization provide abundant O and N groups, and the pore-making process promotes the even distribution of O and N groups in the 3D pore of LPC@PPy, which is favorable for the adsorption of reactive blue 19. The adsorption capacity of LPC@PPy for reactive blue 19 is 537.52 mg g-1, which is 2.04 times the performance of LPC (only hydrothermal and activation process, only have O groups) and 3.36 times that of LC (direct lignin activation, lack of O and N groups). After 8 cycles, LPC@PPy still maintained a high adsorption capacity of 92.14 % for reactive blue 19. In addition, this study found that N and O groups in the material played an important role in adsorption, mainly pyridinic-N, C-OH, -COOR, -C-O- and CC. This work provides a new strategy for the removal of reactive blue 19 and determines the groups that mainly interact with reactive blue 19, which provides a new reference for adsorption, catalysis and related fields.

Utilization of Waste Biomaterial as an Efficient and Eco-Friendly Adsorbent for Solid-Phase Extraction of Pantoprazole Contaminants in Wastewater

The objective of this analysis is to establish the potential of biodegradable agro-industrial waste materials as biosorbents in the solid-phase extraction (SPE) technique for sample preparation. In this regard, waste coffee husk (CH) powder was collected, washed, treated chemically, characterized, and applied as an SPE adsorbent to extract pantoprazole from the wastewater samples. Sample detection was accomplished using the UPLC-MS/MS system. The positive mode of electrospray ionization was exploited for the ionization of the sample, and quantification of the target analyte was performed by the multiple reaction monitoring modes. The precursor to product ion transition of 384.02→1380.05 and 384.02→200.05 was used as qualifiers and quantifiers, respectively. Optimization of the particle size, adsorbent dose, and contact time were evaluated to select the best combination of features. The efficiency and regeneration capability of the CH were compared with respect to a commercially available silica-based C18 SPE adsorbent, and it was found that CH possessed comparable (~50%) extraction, as well as regeneration capacity (~95%). The developed biosorbent was applied in a wastewater sample spiked with the target analyte and recovery studies were performed, which found a range of 93.0 to 102.0% with a %RSD of 3.72 to 12.7%. Thus, CH can be exploited as a ‘greener’ replacement for the commercially available adsorbents for the extraction/retention of active pharmaceutical ingredients present in water/wastewater samples.

Preparation of Breadfruit Leaf Biochar for the Application of Congo Red Dye Removal from Aqueous Solution and Optimization of Factors by RSM-BBD

In this work, biochar produced from breadfruit leaves was utilized to remove the toxic Congo red dye. XRD, FTIR, and FESEM-EDX were implemented to characterize the biochar. Response surface methodology (RSM) and the Box-Behnken design (BBD) techniques were used to evaluate Congo red’s optimum adsorption efficiency. The adsorption of Congo red was studied by varying dye concentrations (5–50 mg/L), times (30–240 min), pH (6–9), and dosages (0.5–2 g/100 mL). X-ray diffractometer results show that the structure of biochar is amorphous. The biochar exhibited unbounded OH, aliphatic CH group, and C=O stretch, as shown by the band peaks at 3340 cm−1, 2924 cm−1, and 1625 cm−1 intensities. RSM-BBD design results showed maximum removal efficiency of 99.96% for Congo red at pH 6.37, dye concentration 45 mg/L, time 105 min, and dosage 1.92 g, respectively. The adsorption of Congo red by biochar was successfully modeled using the Langmuir model and pseudo-second-order model. The biochar produced from breadfruit leaves exhibited a high adsorption capacity of 17.81 mg/g for Congo red adsorption. It suggests that the adsorption is both homogenous monolayer and physicochemical.

Mandarin Biochar-TETA (MBT) prepared from Citrus reticulata peels for adsorption of Acid Yellow 11 dye from water

Dehydration technique with 80% sulfuric acid was used to create a novel biochar from mandarin peel wastes followed by condensate with triethylenetetramine (TETA) to give Mandarin Biochar-TETA (MBT). BJH, BET, FTIR, SEM, DSC, TGA, and EDX studies were used to characterise the MBT. The capacity of the newly developed biochar to remove Acid Yellow 11 (AY11) dye from a water solution was studied. The pH of AY11 dye adsorption was found to be best at pH 1.5. Using 100 ppm AY11 dye as a beginning concentration and 1.75 g L^-1 MBT dose, the greatest percent of AY11 dye removal by MBT was 97.83%. The MBT calculated maximum adsorption capacity (Q_m) was 384.62 mg g^-1. Langmuir (LIM), Freundlich (FIM), Tempkin (TIM), and Dubinin-Radushkevich (DRIM) isotherm models were applied to analyse the experimental data. Furthermore, the results of these isotherm models were investigated by various known error function equations. The MBT experimental data was best suited by the LIM. Pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich kinetic model (EKM), intraparticle diffusion (IPD), and film diffusion (FD) models were used to calculate kinetic data. A PSO rate model with a high correlation (R² > 0.990) was used to assess the adsorption rate. The main mechanism of the MBT adsorption method of the AY11 dye's anions adsorption is the electrostatic attractive forces that arise with the increase of positively charged sites in an acidic medium. The obtained data suggest that the prepared MBT adsorbent has the potential to be an effective material to remove the AY11 dye from water and that it may be used repeatedly without losing its adsorption efficiency.

Study on the Pyrolysis and Adsorption Behavior of Activated Carbon Derived from Waste Polyester Textiles with Different Metal Salts

In this study, the effects of the catalysis of heavy metals on the pyrolysis of waste polyester textiles (WPTs) and the adsorption behaviors of the pyrolysis products of WPTs for Cr(VI) were explored. TG-DTG analysis indicated that the metal ions catalyzed the pyrolysis process by reducing the temperature of the decomposition of WPTs. The surface morphology and pore structure of the carbons were analyzed using SEM and BET. The results demonstrated that Zn-AC possessed the largest specific surface area of 847.87 m²/g. The abundant acidic functional groups on the surface of the activated carbons were proved to be involved in the Cr(VI) adsorption process via FTIR analysis. Cr(VI) adsorption experiments indicated that the adsorption process was more favorable at low pH conditions, and the maximum adsorption capacities of Zn-AC, Fe-AC, and Cu-AC for Cr(VI) were 199.07, 136.25, and 84.47 mg/g, respectively. The FTIR and XPS analyses of the carbons after Cr(VI) adsorption, combined with the adsorption kinetics and isotherm simulations, demonstrated that the adsorption mechanism includes pore filling, an electrostatic effect, a reduction reaction, and complexation. This study showed that metal salts catalyze the pyrolysis processes of WPTs, and the activated carbons derived from waste polyester textiles are promising adsorbents for Cr(VI) removal.

Development of a Novel Green Bio-Nanofluid from Sapindus Saponaria for Enhanced Oil Recovery Processes

The main objective of this study is to develop a novel green-nanofluid from Sapindus Saponaria for its application in enhanced oil recovery (EOR) processes. The bio-nanofluid is composed of a green active compound (AGC), bio-ethanol, and commercial surfactant (SB) at a low concentration. The AGC was obtained from soapberry “Sapindus Saponaria” using the alcoholic extraction method and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and critical micellar concentration (CMC) to verify the content of saponins as active agents with surface-active behavior. Three types of silica-based nanoparticles were used and characterized by FTIR, TGA, and dynamic light scattering (DLS) analysis. Two commercial nanoparticles (SiO2-C1 and SiO2-C2) were evaluated, and a third one (SiO2-RH) was synthesized from rice husks as an ecological nanomaterial alternative. The performance of the adjusted systems was evaluated by capillary number (effective interfacial tension (σe), wettability and viscosity) and finally with coreflooding tests under reservoir conditions. The FTIR results confirm the presence of saponins in the AGC. In addition, according to the TGA, the AGC is stable under the reservoir temperature of interest. Regarding nanoparticles, siloxane and silanol groups were observed in all samples. For SiO2-C1 and SiO2-C2 samples, the weight loss was lower than 5% for temperatures up to 700 °C. Meanwhile, SiO2-RH had a weight loss of 12% at 800 °C, and 8% at reservoir temperature. Results show a decrease in the interfacial tension (IFT) of up to 83% of the tuned system with only 100 mg·L−1 of rice husk nanoparticles compared to the system without nanoparticles, reaching values of 1.60 × 10−1 mN·m−1. In the coreflooding test, increases of up to 13% of additional crude oil were obtained using the best bio-nanofluid. This work presents an excellent opportunity to include green alternatives to improve conventional techniques with added value during the injection of chemicals in chemical-enhanced oil recovery (CEOR) processes.

Treatment on thiodicarb in pesticide wastewater with walnut shells-derived carbon and its improved modification: adsorption behavior

The health problems caused by water pollution cannot be ignored, and the contribution of pesticides to water pollution has also become increasingly unignorable. The modified semi-coke as an adsorbent for reducing pesticide pollution to water was obtained from activated semi-coke which was modified by nitric acid (HNO₃). The semi-coke was obtained by carbonization using 60 mesh walnut shell powder. After acid-base deashing, the semi-coke is dipped into zinc chloride (ZnCl₂) solution to obtain activated semi-coke. Through BET analysis, the specific surface areas of semi-coke, activated semi-coke and modified semi-coke were 26.8 m²/g, 243.9 m²/g, and 339.6 m²/g respectively. An extremely high adsorption capacity of the adsorbents which is used to treat wastewater was achieved. The optimum adsorption conditions for modified semi-coke on thiodicarb solution were 30 mg/L of thiodicarb solution, adsorbent dosage of 0.01 g, adsorption temperature of 25 °C and adsorption time of 90 min. The optimum adsorption amount of 29.54 mg/gsor was achieved (sor is the abbreviation for sorbent). Moreover, through kinetics study, the result manifests that the modified semi-coke adsorption process is more fitted to the second-order kinetic model. This study provided a research implication theoretically for the treatment of pesticides in water.

Sequestration of Hazardous Dyes from Aqueous Solution Using Raw and Modified Agricultural Waste

The continuous degradation of surface water quality by dye materials is of concern globally. Agricultural waste Litchi chinensis (LC) peel in its raw (RL) and modified (CL) forms was used as potential sorbents for sequestration of Congo red (CR) dye from an aqueous solution. The sorbents were characterized before and after sorption with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Brunauer, Emmett, and Teller (BET) surface area analysis, and X-ray diffraction (XRD). Determination of the point of zero charge (PZC) suggested CR dye sorption from an aqueous solution would be best in acidic pH. Batch experimental drivers such as the effects of time, dosage, initial concentration, pH, and temperature were optimized and used. Results from the study showed that modification with citric acid (CA) reduced the equilibration time from 90 to 15 min. Change in water chemistry did not significantly affect the removal efficiency of the sorbent but rather slightly improved it for both sorbent types. The smaller particle size of <125 μm recorded higher removal efficiency than the larger one (>125 μm). The effect of temperature affects the sorption differently. For the RL system, it decreases with an increase in the temperature, while for the CL system it increases with an increase in temperature. The Langmuir isotherm best described the equilibrium data obtained based on the linearized coefficients with maximum sorption capacities ( $q_{\max }$ ) of 55.56 mg/g (RL) and 58.48 mg/g (CL). The pseudo-second-order model also best described the kinetic data. The thermodynamics study showed that the reaction is both feasible and spontaneous. Both sorbents recorded high removal efficiency for other dyes such as rhodamine B, methylene blue, methyl orange, malachite green, and erythrosin B. The five cycled regeneration/sorption experiments with 0.1 M NaOH as the desorbing agent showed that the regenerated sorbents efficiently removed CR dye from an aqueous solution close to their virgin samples for the first three cycles. This research, therefore, establishes LC peel as a potential eco-friendly, readily available, and effective sorbent for sequestration of hazardous dyes from wastewater.

A resin containing motifs of maleic acid and glycine: a super-adsorbent for adsorptive removal of basic dye pararosaniline hydrochloride and Cd(II) from water

The cyclocopolymerization of N,N-diallylglycine hydrochloride, maleic acid and 1,1,4,4-tetraallylpiperazinium dichloride afforded a cross-linked polyzwitterionic acid, which, upon treatment with NaOH, gave the corresponding cross-linked anionic polyelectrolyte (CAPE) in quantitative yield. The pH-responsive resins contained a high density of CO2 - motifs as well as the chelating motifs of glycine residues. The resin CAPE was found to be a super-adsorbent for the removal of pararosaniline hydrochloride (PRH); having a q max of 1534 mg/g. The adsorption process followed pseudo-second-order kinetics and was found to be a nearly irreversible process as suggested by the parameters obtained from Elovich kinetic model. The resin demonstrated excellent adsorption/desorption efficiencies, thereby ensuring its recycling and reuse in potent applications like remediation of industrial dye-waste water. The resin's chelating motifs were also efficient in the adsorptive removal of Cd(II) ions with a q max of 248 mg/g. It was also employed for the simultaneous and effective trapping of Cd(II) and the dye from industrial wastewater. The resin's impressive performance accords it a prestigious place among many sorbents in recent works.

Regenerable magnetic aminated lignin/Fe3O4/La(OH)3 adsorbents for the effective removal of phosphate and glyphosate

Phosphates and organophosphorus cause environmental pollution, and excessive phosphate leads to water eutrophication. Glyphosate, an organophosphorus herbicide, harms the environment and human health. In this study, regenerable magnetic AL/Fe₃O₄/La(OH)₃ adsorbents were developed by modifying Fe₃O₄ and La(OH)₃ on aminated lignin (AL) for phosphate and glyphosate removal. The adsorption capacity for phosphate and glyphosate reached 60.36 mg g^-1 and 83.87 mg g^-1 when the initial concentrations were 150 mg L^-1 and 250 mg L^-1, respectively. The thermodynamic data showed that adsorption is a spontaneous and endothermic process. Adsorption can be applied at pH values ranging from 3 to 11 and is more suitable under acidic conditions. Fe₃O₄ and La(OH)₃ both enhanced the adsorption capacities of phosphate and glyphosate. Phosphate and glyphosate compete slightly when coexisting in the adsorption process at low concentrations. Due to the magnetic properties of Fe₃O₄, the adsorbents can be separated rapidly and effectively with an external magnetic field. 89% adsorption capacity remained after four adsorption-desorption recycles. Thus, AL/Fe₃O₄/La(OH)₃ shows potential for phosphate and glyphosate removal as an effective and reusable adsorbent.

Transforming pods of the species Capparis flexuosa into effective biosorbent to remove blue methylene and bright blue in discontinuous and continuous systems

This study investigates, for the first time, the applicability of seed pods from Capparis flexuosa as an alternative biosorbent to remove methylene blue and bright blue from aqueous medium using continuous and batch systems. The biosorbent was characterized by different techniques, whose particles presented rough surface and large pores and functional groups existing on its surface. In the batch system, an adsorptive capacity of 96.40 mg g^-1 and 80% of methylene blue removal was reached with 0.9 g L^-1 of adsorbent at pH 10, whereas 109.7 mg g^-1 and 83% of bright blue removal was observed using 0.8 g L^-1 of adsorbent at pH 2.0. The Elovich model adjusted the experimental data satisfactorily for both dyes. Tóth model for the MB best described the equilibrium data, and the Langmuir model for the bright blue both favored by the increase of temperature and dyes' concentration. The maximum capacities obtained were 280.78 mg g^-1 and 342.85 mg g^-1 for methylene blue and bright blue, respectively. The thermodynamic parameters indicated spontaneous processes, with endothermic behavior for both dyes. The fixed adsorption experiments using Capparis flexuosa seed pods showed adsorptive capacities of 158.65 and 205.81 mg g^-1 for the methylene blue and bright blue, respectively. The overall results indicated that the pods of the Capparis flexuosa could be an ecological, effective, and economical alternative in the removal of dyes for both continuous and batch systems.

Nano-Intermediate of Magnetite Nanoparticles Supported on Activated Carbon from Spent Coffee Grounds for Treatment of Wastewater from Oil Industry and Energy Production

This work focused on evaluating the adsorptive removal of crude oil using a nano-intermediate based on magnetite nanoparticles supported on activated carbon synthesized from spent coffee grounds and the subsequent catalytic oil decomposition to recover by-products and regenerate the support material. The magnetite nanoparticles were synthesized by the co-precipitation method and were used as active phases on prepared activated carbon. The amount of crude oil adsorbed was determined by adsorption isotherms. In addition, dynamic tests were performed on a packed bed to evaluate the efficiency of the removal process. Thermogravimetric analysis and mass spectrometry were used to evaluate the catalytic powder and the quantification of by-products. Contrasting the results with commercial carbon, the one synthesized from the coffee residue showed a greater affinity for the oil. Likewise, the adsorption capacity increased by doping activated carbon with magnetite nanoparticles, obtaining an efficiency greater than 10%. The crude oil decomposition was carried out successfully by thermal cracking, obtaining a 100% removal. The gas produced after decomposition contains light hydrocarbons such as C2H4 and CH4 and shows a decrease in polluting species such as CO and CO2, leading to greater environmental sustainability of the process.

Effect of dispersant on the synthesis of cotton textile waste-based activated carbon by FeCl2 activation: characterization and adsorption properties

Considering the accumulation and high consumption of activating agents, anhydrous ethanol (AE) could be used to dissolve them to improve the dispersion effect, which was an effective way of improving the practical utilization rate. In this study, FeCl₂ was dissolved in AE and further impregnated cotton textile waste (CTW) to prepare activated carbons (ACs) by pyrolysis. Afterward, ACs prepared in optimal conditions determined by the orthogonal experiment evaluated the physicochemical properties and adsorption capacities for Cr(VI). The results illustrated that AE greatly increased the dispersion of FeCl₂ on CTW, reduced the conventional impregnation dosage, and remarkably improved the activation efficiency. Textural analyses revealed that ACs exhibited excellent porosity properties and graphite carbon structure. FeCl₂ catalyzed the decomposition of volatile substances to produce gaseous products and promoted the transformation of amorphous carbon to graphite carbon that was conducive to pore development, followed by the formation of developed micropores and crystal structures. The adsorption performance of ACs was estimated using Cr(VI), and the adsorption was fitted with the pseudo-second-order kinetic and the Langmuir isotherm. Furthermore, the ACs possessed superior magnetization and reusability. Graphical abstract.

Batch interaction of emerging tetracycline contaminant with novel phosphoric acid activated corn straw porous carbon: Adsorption rate and nature of mechanism

In this work, corn straw (CS) based porous carbon was prepared by one-step phosphoric acid (H₃PO₄) low temperature activation. The impregnation ratios (H₃PO₄/CS, g/g) played an important role in the pore development. ACS_300-1 engineered at 300 °C and the impregnation ratio of 1.0 showed the maximal specific surface area of 463.89 m²/g with total pore volume of 0.387 cm³/g, attaining a high tetracycline (TC) uptake of 227.3 mg/g. The adsorption of TC onto ACS_300-1 was found tolerant with wide pH (2.0-10.0) and high ionic strength (0 - 0.5 M). The adsorption data can be fitted well by the pseudo-second order kinetic model and Langmuir isotherm model. The endothermic and spontaneous properties of the adsorption system was implied by Thermodynamic study. The findings of the current work conclude that one-step H₃PO₄ activation is a green and promising method for corn straw based porous carbon that may be found with great potentials in antibiotic containing wastewater treatment.

Nano-cerium oxide functionalized biochar for phosphate retention: preparation, optimization and rice paddy application

In this study, nano-cerium oxide functionalized maize straw biochar (Ce-MSB) was prepared and utilized to remove P from agricultural wastewater. Response Surface Model was applied to optimize the operating conditions. Moreover, Ce-MSB was applied to actual rice paddy column for the first time. Response Surface Model (RSM) showed higher materials ratio had positive effect on PO₄^3- adsorption capacity, while higher pyrolysis temperature had negative effect. The maximum adsorption capacity of Ce-MSB for PO₄^3- was 78 mg g^-1, implying that Ce-MSB was an effective functionalized adsorbent for P removal. Paddy soil column experiment showed that application of Ce-MSB decreased total phosphorus concentration of surface water by 27.33% and increased total phosphors (TP) content of top soil by 7.22%. Further, Ce-MSB tends to increase rice plant height and leaf area. Therefore, Ce-MSB can be used as a promising functionalized biochar to reduce the risk of phosphorus loss from paddy field surface running water.

Behavior of mesoporous activated carbon used as a remover in Congo red adsorption process

The adsorption characteristics of Congo red (CR) dye on activated carbon produced under optimized conditions from tomato paste waste were evaluated. The effects of adsorbent dose, initial dye concentration, contact time, ionic strength and solution temperature on adsorption were investigated. Adsorption kinetic was better described by the pseudo-first order model. Results of the intra-particle diffusion model show that the pore diffusion is not the only rate-limiting step. Adsorption isotherm was well defined by the Langmuir isotherm. The maximum adsorption capacity of the activated carbon was 435 mg g^-1 at 328 K. The dimensionless separation factor R_L revealed the favorable nature of the isotherm of the activated carbon-dye system. Adsorption energy was found to be 4.20-4.55 kJ mol^-1 indicating that the mechanism of adsorption is physical in nature. Thermodynamic studies showed that CR adsorption onto activated carbon was feasible, spontaneous and endothermic. Desorption of the used activated carbon was studied using ethanol as solvent and desorption efficiency of 56.4% was obtained after five cycles. The findings indicated that the activated carbon is a very effective and low-cost adsorbent for removal of CR dye from aqueous solutions.

Adsorption of quinolone, tetracycline, and penicillin antibiotics from aqueous solution using activated carbons: Review

Antibiotics, an important type of pharmaceutical pollutant, have attracted many researchers to the study of their removal from aqueous solutions. Activated carbon (AC) has been widely used as highly effective adsorbent for antibiotics because of its large specific surface area, high porosity, and favorable pore size distribution. In this article, the adsorption performance of AC towards three major types of antibiotics such as tetracyclines, quinolones, and penicillins were reviewed. According to collected data, maximum adsorption capacities of 1340.8, 638.6, and 570.4mg/g were reported for tetracyclines, quinolones, and penicillins, respectively. The values of 1/n for Freundlich isotherm were less than unity, suggesting that the adsorption was nonlinear and favorable. Adsorption kinetics followed closely the pseudo-second-order model and analysis using the Weber-Morris model revealed that the intra-particle diffusion was not the only rate controlling step. AC adsorption demonstrated superior performance for all selected drugs, thus being efficient technology for treatment of these pollutants.

Utilization of Euryale ferox Salisbury seed shell for removal of basic fuchsin dye from water: equilibrium and kinetics investigation

Euryale ferox Salisbury (E. ferox) is an environmentally and economically important wetland macrophyte.

Effective removal of tetracycline from aqueous solution using activated carbon prepared from tomato (Lycopersicon esculentum Mill.) industrial processing waste

Activated carbon (TAC) prepared under optimized conditions with ZnCl2 activation from a new precursor; tomato industrial processing waste (TW), was applied as an adsorbent to remove tetracycline (TC) from aqueous solution. The factors (TAC dosage, initial TC concentration, contact time, ionic strength and solution temperature) affecting the adsorption process were examined at natural pH (5.7) of TAC-TC system in aqueous solution. Kinetic data was found to be best complied by the pseudo-second order model. The isotherm analysis indicated that the equilibrium data could be represented by the Langmuir model. The maximum adsorption capacity was identified as 500.0mgg(-1) at 308K.

Gd0.5Y0.5CrO3 Perovskite-Type Oxide Nanopowder: A Novel Adsorbent to Remove Organic Dye from Aqueous Media

Nanoparticles of perovskite-type Gd0.5Y0.5CrO3 were prepared by the sol–gel method and tested for dye removal from aqueous media. The structure and morphology of Gd0.5Y0.5CrO3 nanopowders were characterised using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, the Brunauer–Emmett–Teller technique, thermal gravimetric analysis-differential thermal analysis and infrared spectroscopy. The ability of calcined nanoparticles to remove bromothymol blue (BTB) dye from aqueous solution was assessed. Adsorption experiments were carried out systematically by batch experiments to investigate the influence of different factors, such as contact time, initial concentration of dye, various adsorbent doses and pH of the solutions. The dye removal efficiency was found to be decreased with an increase in initial pH of the dye solution and Gd0.5Y0.5CrO3 nanoparticles exhibited good dye removal efficiency at acidic pH, optimized at pH 2. Kinetic adsorption data were studied using three most popular isotherm models, namely Langmuir, Freundlich and Redlich–Peterson. A non-linear method was used for comparing the best fit of the isotherms. The best fit was found for the Redlich– Peterson isotherm. The maximum predicted adsorption capacity was 366.67 mg−1 for BTB. In addition experimental results indicated that the adsorption kinetic data followed a pseudo second-order rate for the tested dye.

Facile controllable hydrothermal route for a porous CoMn2O4 nanostructure: synthesis, characterization, and textile dye removal from aqueous media

We herein report the synthesis of a pure sphere-like spinel CoMn₂O₄ nanostructure using a facile and surfactant-free hydrothermal approach followed by a thermal decomposition of the as-prepared CoCO₃/MnCO₃ composite precursor.

Preparation of magnetic porous carbon from waste hydrochar by simultaneous activation and magnetization for tetracycline removal

In the present work, a novel magnetic porous carbon (MPC) with maghemite (γ-Fe2O3) particles is facilely prepared from hydrochar (a solid residue of hydrothermal carbonization of biomass) in one step through simultaneous activation and magnetization. The resultant MPC is characterized and utilized as an adsorbent for tetracycline (TC) removal from aqueous solutions. The BET surface area and micropore volume of the MPC are found to be 349 m(2)g(-1) and 0.16 cm(3)g(-1), respectively. The adsorption kinetics data could be well described by the pseudo-second-order model, and the TC adsorption onto MPC is an endothermic and spontaneous process. The enhanced surface area of the MPC, as well as its graphite-like structure, may contribute to the adsorption capacity of TC. After adsorption, MPC could be effectively separated by applying a magnetic field.

In situ bioremediation of surface waters by periphytons

Environmentally benign and sustainable biomeasures have become attractive options for the in situ remediation of polluted surface waters. In this paper, we review the current state of reported experiments utilizing naturally occurring periphyton. These are microbial communities consisting of heterotrophic and photoautotrophic microorganisms that are reportedly capable of remediating surface waters which suffer from pollution due to a variety of contaminants. In our review, we focus on four aspects of bioremediation: multiple contaminant removal, the processes involved in contaminant removal, successful cell immobilization technologies and finally, the consideration of safety in aquaculture. It has been noted that recent developments in immobilization technologies offer a fresh approach facilitating the application of periphyton. The use of periphyton biofilm overcomes several disadvantages of single species microbial aggregates. The inclusion of periphyton, as a stable micro-ecosystem, is a promising in situ strategy to restore decimated surface water ecosystems.

Adsorption of dyestuff from aqueous solutions through oxalic acid-modified swede rape straw: adsorption process and disposal methodology of depleted bioadsorbents

Swede rape straw (Brassica napus L.) was modified by oxalic acid under mild conditions producing an efficient dye adsorbent (SRSOA). This low-cost and environmental friendly bioadsorbent was characterized by various techniques and then applied to purify dye-contaminated aqueous solutions. Equilibrium study showed that the Langmuir model demonstrated the best fit to the equilibrium data and the methylene blue (MB) adsorption capacity calculated by this model was 432mgg(-1). The adsorption process and mechanism is also discussed. To properly deal with the dye-loaded bioadsorbents, the disposal methodology is discussed and a biochar based on depleted bioadsorbents was for the first time produced and examined. This method both solved the disposal problem of contaminant-loaded bioadsorbents and produced an useful adsorbent thereafter. The study indicates that SRSOA is a promising substitute for ACs in purifying dye-contaminated wastewater and that producing biochars from contaminant-loaded bioadsorbents maybe a feasible disposal method.