Initial Adsorbate Concentration Research Articles

ENHANCING BIOADSORPTION EFFICIENCY OF PEANUT SKIN BASED ON PHYSICAL AND CHEMICAL ACTIVATION METHODS IN FE2+ ION REMOVAL USING COLUMN TECHNIQUE IN ARTIFICIAL WASTEWATER

In the interest of efficient heavy metal ion removal from water, various methods such as aeration, coagulation, filtration, sedimentation, and adsorption have been thoroughly investigated. Adsorption, specifically the column method with groundnut shell powder as a bio adsorbent, stands out as a practical, effective, and efficient approach. In this study, a fixed variable of 50 g adsorbent, a particle size of 35 mesh, and an initial adsorbate concentration of 100 ppm was used, along with a 10-liter adsorbate volume and a flow rate of 4 liters per minute. Sampling intervals of 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, and 150 minutes were chosen, and the independent variables encompassed untreated adsorbents, physically activated adsorbents, and chemically activated adsorbents using 1N H2SO4 and 1N NaOH. The outcomes revealed that the adsorption of Fe2+ was notably influenced by the type of activator. The highest Fe2+ removal percentage, 55.90%, was achieved at 135 minutes, showcasing the efficacy of the bioadsorption process. Notably, the optimal bioadsorbent activation was attained using 1N NaOH. This study provides valuable insights into the dynamics of heavy metal ion removal, emphasizing the significance of bioadsorption with groundnut shell powder and underscoring the impact of specific activation methods on the efficiency of the adsorption process.

Adsorptive uptake of thymol blue from aqueous medium using calcined snail shells: equilibrium, kinetic, thermodynamic, neuro-fuzzy and DFT studies

ABSTRACTS The spontaneous discharge of pollutants or toxicants into the ecosystem as a result of various anthropogenic activities is alarming, this necessitates a drastic cheap, and eco-friendly clean-up approach. Out of all the methods, adsorption has proven to be the most effective. The batch adsorptive removal of Thymol Blue (TB) dye from aqueous solutions is examined in this study utilizing calcined snail shells (CalSS). With the aid of SEM, EDS, XRD, and FTIR, the synthesized adsorbent was examined for different physicochemical characteristics. A machine learning model namely Adaptive Neuro-Fuzzy Inference System (ANFIS) was developed to assess the TB adsorption process while taking into account the important adsorption parameters contact time, temperature, pH, adsorbent dosage, then initial adsorbate concentration. Adsorbent pHpzc was also evaluated. EDX and FTIR confirm the formation of CaO with sharp peaks at 547 cm−1 and C–O and O–H are present. SEM and XRD show an irregularly shaped highly crystalline adsorbent material having a typical particle size of 65 ± 2.81 nm and lattice parameter value of 8.611617 Å. The pHpzc value is 11.04, indicating basic surface characteristics. The pH of 3.0, an adsorbent dose of 10 mg and the highest achievable adsorption efficiency were measured to be 98.75% at 20 °C. The findings from the study fit nicely onto Brouser Sotolongo with q BS = 259.4887 mg/g and R 2 = 0.9888. The pseudosecond order model (PSOM) recorded the least error value of 0.3336 and R 2 = 0.9952. This indicates chemisorption and multilayer adsorption processes. The thermodynamic parameters ΔH° and ΔG° demonstrate the exothermic and spontaneous nature of the adsorption process. The ANFIS model for the TB sequestration was evaluated using relevant statistical metrics, giving Root Mean Square Error (RMSE) value of 1.4644, Mean Absolute Deviation (MAD) value of 0.576, Mean Absolute Error (MAE) value of 1.2974 and Mean Absolute Percentage Error (MAPE) value of 1.5141. This outcome revealed that the ANFIS model and experimental findings are in good agreement. The efficacy of calcined snail shell in removing Thymol Blue dye from aqueous solution was also examined using in-silico technique which was in accordance to the value of the calculated descriptors obtained from the adsorbent as well as the calculated binding affinity. The elimination of TB-polluted wastewater using calcined snail shells is demonstrated in this study to be a successful and environmentally benign process.

Green synthesis of iron (III) oxide (Fe3O4) Nanoparticles Using Citrus sinensis Peel Extract for the Removal of Ciprofloxacin in Water

Ciprofloxacin is a widely used antibiotic that can contaminate water sources and pose environmental and health risks. Therefore, the objective of this paper is to explore the green synthesis of iron (III) oxide nanoparticles using Citrus sinensis peel extract for the removal of ciprofloxacin in water using standard techniques. The adsorption of ciprofloxacin on the nanoparticles was investigated under different conditions, such as pH, initial concentration of adsorbate, contact time, and different adsorbent doses. The adsorption data were fitted to different isotherm and kinetic models to understand the adsorption mechanism and parameters. The results of characterization revealed the particles to be of nanocrystalline structure with a cubic crystal shape, negative surface charge, and a high thermal stability with elemental composition primarily of Fe and O; it has z- average of 42.60, with Fe-O bond at 693.30cm-1 and UV-Visible absorbance at 221nm. The maximum adsorption capacity with ciprofloxacin was 29.21 mg/g (97.45%) at pH of 7 and room temperature of 25 °C. The results of the adsorption data indicated that the adsorption followed the Langmuir isotherm model and the pseudo-second-order kinetic model, suggesting a monolayer adsorption on a homogeneous surface with a finite number of identical sites. The synthesized nanoparticles showed a high efficiency and selectivity for the removal of ciprofloxacin from water, demonstrating it potential as an eco-friendly and low-cost adsorbent for water purification.

Custom and definitive screening designs for evaluating multiple adsorbents: bisphenol-A adsorption onto villi-structured polyaniline/carboxymethyl cellulose composites

ABSTRACT Polyaniline composites consisting of carboxymethyl cellulose (CMC) have enhanced adsorption properties, but recent studies indicate that the oxidised species – dialdehyde carboxymethyl cellulose (DCMC) – outperforms CMC-based composites. However, these studies fail to study the effect of DCMC's aldehyde content and compare the composites with CMC-based composites; numerous experiments required to investigate each adsorbent for each factor limit such studies. We explored a way to study whether villi-structured polyaniline (VSPANI), its CMC composite (CMC/PANI), and its DCMC composites with 35% (DCMC(A)/PANI) and 77% (DCMC(B)/PANI) aldehyde content would be great adsorbents for removing bisphenol-A (BPA). We first customised a D-optimal screening design to alleviate the pitfalls of definitive screening design (DSD), hence estimating all the main effects: initial concentration, pH, flow rate, adsorbent amount, sample volume and type of adsorbent. We excluded CMC/PANI and DCMC(A)/PANI composites, both with low adsorption capacities of 56.57 and 57.27 mg/g from further investigation. The DSD followed to estimate all second-order effects through which we projected a response surface method (RSM) to optimise and model the active factors. Increasing the aldehyde content on the composites favoured adsorption, but there lacked evidence to suggest VSPANI and DCMC(B)/PANI differed significantly in performance. The models were numerically and graphically proven adequate, explaining 80% and 99% of the variation when predicting removal efficiency and adsorption capacity. VSPANI showed potential as an adsorbent for BPA removal with 85% removal efficiency and 129 mg/g adsorption capacity. This comprehensive approach, combining both designs, allows for sustainable investigation of multiple adsorbents and factors, minimising experimental waste.

Remediation of toluidine blue O dye from aqueous solution using surface functionalized magnetite nanoparticles

Abstract In the current study, tannic acid-functionalized iron oxide nanoparticles have been synthesized using a cost-effective co-precipitation method and subsequently characterized using various instrumentation techniques such as Fourier transform infrared spectroscopy, X-ray diffractometer, field emission scanning electron microscopy, and thermal gravimetric analysis. Further, these surface-modified magnetite nanoparticles have been used for the adsorption of toluidine dye from an aqueous solution. The adsorption process was accompanied using batch procedure, and influences of several factors such as adsorbent dose, contact time, pH, temperature, and initial concentration of adsorbate were inspected concurrently. The maximum adsorption capacity of tannic acid-functionalized magnetite nanoparticles was found to be 50.68 mg/g. The adsorption process was observed to follow the Temkin isotherm model, whereas the kinetic study was well described by pseudo-second order. The thermodynamic study revealed the adsorption process to be endothermic and spontaneous in nature with a high degree of freedom between adsorbent and adsorbate. Therefore, the study indicated that the tannic acid-functionalized magnetite nanoparticles have promising adsorption capability and can be used as an excellent adsorbent for the removal of toluidine blue O dye from the aqueous solution.

Magnetic graphene derivates for efficient herbicide removal from aqueous solution through adsorption.

2,4-Dichlorophenoxyacetic acid (2,4-D) is an herbicide and is among the most widely distributed pollutant in the environment and wastewater. Herein is presented a complete comparison of adsorption performance between two different magnetic carbon nanomaterials: graphene oxide (GO) and its reduced form (rGO). Magnetic functionalization was performed employing a coprecipitation method, using only one source of Fe2+, requiring low energy, and potentially allowing the control of the amount of incorporated magnetite. For the first time in literature, a green reduction approach for GO with and without Fe3O4, maintaining the magnetic behavior after the reaction, and an adsorption performance comparison between both carbon nanomaterials are demonstrated. The nanoadsorbents were characterized by FTIR, XRD, Raman, VSM, XPS, and SEM analyses, which demonstrates the successful synthesis of graphene derivate, with different amounts of incorporate magnetite, resulting in distinct magnetization values. The reduction was confirmed by XPS and FTIR techniques. The type of adsorbent reveals that the amount of magnetite on nanomaterial surfaces has significant influence on adsorption capacity and removal efficiency. The procedure demonstrated that the best performance, for magnetic nanocomposites, was obtained by GO∙Fe3O4 1:1 and rGO∙Fe3O4 1:1, presenting values of removal percentage of 70.49 and 91.19%, respectively. The highest adsorption capacity was reached at pH 2.0 for GO∙Fe3O4 1:1 (69.98mgg-1) and rGO∙Fe3O4 1:1 (89.27mgg-1), through different interactions: π-π, cation-π, and hydrogen bonds. The adsorption phenomenon exhibited a high dependence on pH, initial concentration of adsorbate, and coexisting ions. Sips and PSO models demonstrate the best adjustment for experimental data, suggesting a heterogeneous surface and different energy sites, respectively. The thermodynamic parameters showed that the process was spontaneous and exothermic. Finally, the nanoadsorbents demonstrated a high efficiency in 2,4-D adsorption even after five adsorption/desorption cycles.

Absorbance Enhancement of a Treated Tanzanian kaolin for Removal of Synthetic Dyes from Water

The absorbance efficiency of local kaolin clay from Tanzania (Pugu kaolin) has been enhanced to improve its utilization in removal of textile dyes from water. The clay was acid-activated using H2SO4, after calcination at 750oC. Characterization by XRF, XRD, ATR-FTIR and Porosimeter showed kaolinite [Al2Si2O5(OH)4], silica (SiO2) and microcline [KAlSi3O8] as the main phases. Upon acid treatment, silica increased from 44.18% to 58.81% due to the appearance of tridymite, and alumina decreased from 26.70% to 12.74% due to disappearance of the kaolinite. Surface area increased from 15.36 to 149.61 m2 /g due to removal of acid-soluble impurities. The chemical composition showed decrease of Fe2O3 and increase of other major oxides. The impact of acid-activation on contact time, temperature, adsorbent dose, initial pH and absorbate concentration was investigated through batch adsorption technique using basic blue 9 (BB9) and direct red 28 (DR28) dyes. The results at optimal conditions of 3 hours contact time, 27oC temperature, 0.9 g adsorbent dose, initial pH of 11 and initial adsorbate concentration of 90 mg/L, showed that acid modification of the clay increased its capacity to adsorb BB9 from 96.82% to 99.91%, and DR28 from 86.33% to 95.04%. These findings established the influence of modifying the raw clay for its dye removal applications.

Adsorption Investigations on the Removal of Azoic Dye by Untreated Wood Sawdust

Batch adsorption of the azoic dye Congo red (CR) was carried out successfully on untreated low-cost wood sawdust. The impact of several variables (contact time, amount of solid adsorbent, initial adsorbate concentration, temperature, and pH) on the sorption process was studied. A maximum removal efficiency was achieved after 50 minutes at pH = 5 and 25 °C. To characterize the adsorbent, FTIR, SEM, EDX, and BET analyses were performed. The equilibrium isotherms were described using four alternative models. The data were found to fit the Freundlich model the best. The kinetic analysis demonstrates that the process is best represented by a pseudo-second-order model. The thermodynamic studies revealed the spontaneity and the exothermic nature of the sorption process. The optimal isotherm model served as the foundation for the design of a one-stage batch adsorber for the sorption of CR onto wood sawdust.

Batch adsorption study of Congo Red dye using unmodified Azadirachta indica leaves: isotherms and kinetics

Abstract A low-cost adsorbent developed from unmodified Azadirachta indica leaves was used for adsorptive removal of the Congo Red dye from an aqueous medium. The adsorbent was characterized by the Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM) techniques. For optimization of operational parameters such as dye concentration, solution pH, adsorbent dose, contact time, and temperature, batch adsorption experiments were performed. It was found that for neem leaves powder (NLP), the optimum conditions were as follows: adsorbent dose of 0.8 g, contact time of 100 min having a solution with pH value of 5, adsorbate initial concentration of 40 ppm at temperature 60 °C where maximum amount of dye, i.e., 84%, removal was observed. The process followed pseudo-first-order kinetics, which reveals physical adsorption. According to isothermal investigations, sorption data were best fit with the Freundlich isotherm model. Thermodynamically, the adsorption of the Congo Red dye by the neem leaf powder was exothermic. Furthermore, the mechanistic removal of the Congo Red dye by the NLP has been explored with the help of the surface complex formation (PHREEQC) mechanism. Overall, the results of the study explore the promising nature of NLP for Congo Red dye removal.

Evaluation of the adsorption capacity of surfactant-modified biomass in an aqueous acid blue 193 system

The study explored the capacity of modified pinewood dust (S-dust) for adsorbing acid blue 193 dye. The novel adsorbent was prepared via the insitu intercalation of quaternized ammonium copolymer (cationic surfactant) onto pinewood dust. The synthesized biosorbent was characterized using the Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersion X-ray (EDX) and Brunauer–Emmett–Teller (BET) surface area equipment. To establish the variable effects on the dye uptake, the ranges of solution pH, initial adsorbate concentration, contact time and adsorbent dosage were varied. The maximum monolayer adsorption capacity of 117.58 mg/g was recorded at pH 4.0, 0.1 g/L adsorbent dose and 2 h sorption duration. The process kinetics and isotherm modelling fitted best to the pseudo-first-order and Freundlich models, respectively. From the mechanistic/diffusion studies, intraparticle and pore diffusion mechanisms were respectively postulated at low and high initial adsorbate concentrations. Also, the occurrence of a nonspontaneous endothermic uptake process was inferred from the thermodynamics evaluations. Therefore, the effective acid blue 193 dye uptake onto novel S-dust was confirmed in this study.

The potential capability of treated perlite for removal of penta chloro nitrobenzene

Abstract Perlite is an example of clayey type geologic mineral. Perlite is a cheap and abundant adsorbent and it can be used for versatile applications in food, pharmacy and chemistry industries. Perlite was chosen for the removal of penta chloro nitrobenzene (PCNB) pesticide. This pesticide is used for the control of fungi species in farming commonly. Adsorbent surface area and pore volumes were determined as 288.15 m2/g and 78.24 cm3/g (BET method). The characteristics of the adsorbent were furnished by evaluating the SEM and FTIR images. The adsorption equilibrium was reached in 80 min. Initial adsorbate concentration and pH of the medium were also investigated from this point of view. The experimental data were evaluated with proper isotherm models such as Langmuir, Freundlich and Halsey. Langmuir and Freundlich isotherms give the best results. Monolayer capacity was found as 238.095 mg/g. The kinetic mechanisms of the phenomon was analyzed by employing the pseudo first and second order models. Pseudo first order kinetic results were better than the second one with the higher regression coefficients and close experimental and calculated uptake values. Those values were found as 0.615 and 0.6587 mg/g for 1 μg/mL aqueous pesticide solution. Activation energy was found approximately 5094 J/mol which was shown a physisorption mechanism of the adsorption. Activation energy is also employed for interpreting the sticking probability factor. The thermodynamic of adsorption were also evaluated and found as −2.385 J/g at the room temperature. The negative Gibbs energy shows the feasibility and spontaneous nature of PCNB removal on perlite.

Absorbance enhancement of a treated Tanzanian kaolin for removal of synthetic dyes from contaminated water

Kaolin possesses unique features suitable for removing pollutants from aqueous solutions, in this regard, improving its effectiveness as an adsorbent is important. This study focused on refining the absorbance efficiency of Pugu kaolin clay from Tanzania to enhance its utilization in removing textile dyes from contaminated water. The process involved acid-activation after calcination at 750oC. Characterization using X-ray Fluorescence (XRF), X-ray diffraction (XRD), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Porosimeter techniques revealed the presence of kaolinite [Al2Si2O5(OH)4], silica (SiO2) and microcline [KAlSi3O8] as the main phases. Acid treatment resulted in an increase in silica content from 44.18% to 58.81% due to the appearance of tridymite, while alumina decreased from 26.70% to 12.74% due to the removal of kaolinite. Surface area significantly expanded from 15.36 to 149.61 m2/g as acid-soluble impurities were eliminated. Chemical composition was also altered, with a decrease in Fe2O3 and increase in other major oxides. The impact of acid activation on the adsorption capacity of the clay was investigated by studying various parameters such as contact time, temperature, adsorbent dose, initial pH and adsorbate concentration. Basic Blue 9 (BB9) and Direct Red 28 (DR28) dyes were used as model adsorbates. The results obtained at optimal conditions of 3 hours contact time, 27oC temperature, 0.9 g adsorbent dose, initial pH of 11 and initial adsorbate concentration of 90 mg/L, showed that acid modification of the clay increased its capacity to adsorb BB9 from 96.82% to 99.91%, and DR28 from 86.33% to 95.04%. These findings underscore the positive impact of modifying the raw clay, enhancing its suitability for dye removal applications.

Removing fluoride ions from wastewater by Fe3O4 nanoparticles: Modified Rhodophytes (red algae) as biochar

The present study seeks to utilize the biochar prepared from red algae (AR) and its composite with iron oxide (Fe3O4)-nanoparticle (MBC-AR) to estimate their batch extent potential decontamination mechanism for fluoride ion removal from aqueous solution. Various characterization techniques have been analyzed to study the functional groups, including FT-IR, XRD, EDS, SEM, FE-SEM, TEM and VSM of the synthesized adsorbent (MBC-AR). Several adequate batch adsorption studies were performed to ascertain the equilibrium state. The research yielded a well-established langmuir adsorption isotherm with a capacity for adsorption of 96.4 mg/g, and it suited well to a pseudo-second-order kinetic model. According to reports, the MBC-AR is a useful bio-adsorbent for eliminating fluoride ions from wastewater and other large-scale uses. At room temperature (298 K), the effects of bio-adsorbent doses (10–150 mg), initial concentration of adsorbate taken (20–80 mg/L), pH value (2.0–10.0), as well as contact time (0–250 min) were assessed for fluoride removal using MBC-AR. The efficacy of adsorption and its statistical data were well-established with a pseudo-second-order mechanism and Langmuir isotherm (R2 = 0.99). It was determined that the highest adsorption efficacy and capacity were 96.4 mg/g in the phase equilibrium process.

A sustainable and highly efficient fossil-free carbon from olive stones for emerging contaminants removal from different water matrices

The olive stone is a large waste product of the olive oil extraction industry. The present study investigates developing activated carbon from olive stone waste (OSAC) to remove pharmaceuticals from water. Different temperatures and olive stone: KOH ratios were studied. The OSAC produced at 750 °C and 1:3 ratio was found to have the highest porosity and surface area and was tested in the adsorption process. Diclofenac and ciprofloxacin were selected as model contaminants. The adsorption process was optimized with regards to OSAC dosage, pH, temperature, and initial concentration of adsorbate. The OSAC was found to be effective for a wide pH range (2–11) with an optimum dosage of 1 g/L at 25 °C. The pharmaceuticals were almost completely removed in 75 min. The adsorption was endothermic and followed first-order kinetics with physical mechanisms such as electrostatic possibly being the main driver. The optimum conditions were applied to test the removal of diclofenac and ciprofloxacin in synthetic water, lake water (Lake Balaton, Hungary) and secondary wastewater for seven cycles. There was little difference between the removal of the tested water matrices highlighting the potency of OSAC as an adsorbent for pharmaceutical removal in industrial applications. The removal dropped from >99% for the first cycle to 20–30% for the seventh cycle.

Parameter Influence, Characterization and Adsorption Mechanism Studies of Alkaline-Hydrolyzed Garcinia kola Hull Particles for Cr(VI) Sequestration.

Despite the regulations by The World Health Organization (WHO) on the permissible limit of chromium, many industries still discharge wastewater polluted with chromium into the environment irrationally. This poses a lot of risk to aquatic lives and humans because of its carcinogenic and toxic attributes. Thus, treatment of industrial wastewater polluted with chromium is highly imperative before its disposal. Nonetheless, the hulls generated from Garcinia kola in our various farmlands also causes environmental pollution when dumped unknowingly. In this present study, Garcinia kola hull particles (GK-HP) was hydrolyzed using NaOH and applied as adsorbent for Cr(VI) sequestration. The raw Garcinia kola hull particles (rGK-HP) and modified Garcinia kola hull particles (cMGK-HP) were characterized using Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), powder X-ray diffractometry (XRD), Fourier-Transform-Infrared (FTIR), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS) and point of zero charge (pHpzc). The influence of pH, adsorbent dose, contact time, temperature and adsorbate initial concentration on Cr(VI) sequestration were examined. The cMGK-HP was able to remove 96.25% of Cr(VI) from solution and proved to be effective than rGK-HP. The amount of Cr(VI) removed from solution decreased as the pH and adsorbate initial concentration were increased. However, the amount increased as the adsorbent dose, contact time and temperature were increased. Change in morphological structure, textural property, spectral peak, phase composition and adsorbents chemical composition before and after Cr(VI) sequestration from solution were proved by SEM, BET, FTIR, XRD, and EDS analyses respectively. The isotherm and kinetic studies suggest Cr(VI) adsorption on adsorbents' surface to be monolayer in nature and adsorption data to be well-fitted into pseudo second order model respectively. The cMGK-HP possessed excellent reusability attribute and high thermal stability as shown by TGA. In conclusion, cMGK-HP could effectively be used as an adsorbent for Cr(VI) sequestration from solution.

Kinetic, isotherm and thermodynamic studies of the adsorption of phenol and tyrosine onto apatitic tricalcium phosphate

The present study was conducted to evaluate the feasibility of apatitic tricalcium phosphate with a Ca/P ratio of 1.50 for the adsorption of phenol and tyrosine from aqueous solutions. The adsorbent was synthesized at room temperature using an aqueous double decomposition method and characterized through physicochemical methods. Batch adsorption studies were conducted as a function of contact time, initial adsorbate concentration, temperature, and pH. The adsorption kinetics of phenol and tyrosine were well fitted to the pseudo-second-order model. The maximum adsorption capacity was found to be 5.56 mg/g for phenol and 9.65 for tyrosine mg/g at 298 K. The adsorption of phenol and tyrosine was well explained using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevick models. The Langmuir model is the most suitable, with a maximum monolayer adsorption capacity of 7.32 mg/g for phenol and 11.43 mg/g for tyrosine at 298 K. The thermodynamic parameters indicate that the adsorption process is favorable, spontaneous, exothermic, and controlled by physisorption with electrostatic interactions between compounds containing the phenolic group and apatite. The results of this study have demonstrated the potential utility of apatitic tricalcium phosphate, which could be developed into a viable technology for the adsorption of compounds containing the phenolic group from aqueous solutions.

ADSORPTION OF BEMACID RED DYE FROM AQUEOUS SOLUTIONS ON COAL FLY ASH MODIFIED WITH HYDROCHLORIC ACID

<p>The adsorption process gives great results for the removal of different types of colored substances or different, mainly organic pollutants from wastewater. In addition to standard adsorbents (such as activated carbon), cheap and natural adsorbents have been increasingly used in recent times (e.g. clay, zeolites), along with waste materials (fly ash from thermal power plants or different agricultural/plant remains), after proper preparation and modification. Research presented in this article was performed with fly ash from thermal power plant Stanari. The aim of this study was to investigate the possibility of removing Bemacid Red (BR) dye from textile industry wastewater by adsorption on fly ash modified with HCl. After a series of experiments, the optimal process parameters were determined. These parameters were then applied to a wastewater sample obtained by simulating polyamide fabric dyeing. The efficiency of adsorption of BR dyes from aqueous solutions depends directly on the process parameters: contact time, pH value, adsorbent dose and initial adsorbate concentration (dye concentration). Under optimal process conditions, a dye removal rate of 97.1 % was achieved. Analyzing the experimentally obtained data using nonlinear adsorption isotherms, a much better agreement of the Freundlich model with the experimental results was determined (the coefficient of determination is R<sup>2</sup>=0.9787). The obtained data show that the adsorption of Bemacid Red dye on fly ash is multilayered. Optimal parameters of the adsorption process were applied to wastewater obtained by simulating the process of dyeing polyamide fabric with BR dye. The efficiency of adsorption under defined conditions was confirmed through the 100 % removal of dye from a real wastewater sample.</p>

Porous Carrageenan-Derived Carbons for Removal of Pb(II) Ions from Aqueous Solution

Activated carbon (AC) is a widely used adsorbent that can be applied to remove lead (Pb(II)) ions from wastewater. In the current work, carrageenan was used as a precursor to prepare carraggenan based activated carbon (CAC) using potassium hydroxide (KOH) as a chemical activating agent for Pb(II) ions adsorption from aqueous solution of lead nitrate (Pb(NO3)2). The preparation process involved activation of the carrageenan with KOH at a ratio of 1:4 followed by carbonization at 700oC for 4 h. Physical and chemical characterization of synthesized CAC was conducted to understand surface morphology and functional groups. As the scanning electron microscope (SEM) analysis found, the CAC particle sizes are, on average 25.11 µm before adsorption and 39.21 µm after adsorption. Functional group studies proved that the adsorbate had been adsorbed into the CAC by showing a band stretch of the nitrile group in the Fourier transform infrared (FTIR) spectroscopy analysis. The adsorption process was optimized by changing the temperature of adsorption, dosage of adsorbent, and initial concentration of adsorbate. At the optimum conditions, maximum Pb(II) ions adsorption on the CAC was achieved by 99.04%. Throughout this study, the highest capacity of CAC was determined to be 1.95 mg/g, while the minimum capacity was found to be 0.19 mg/g. Langmuir and Freundlich isotherm were studied to understand adsorption mechanisms. The results suggested that the Langmuir isotherm model fits better than the Freundlich model with a regression coefficient of 0.9845. Pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. Pseudo-second-order exhibited the best fit data for kinetic studies with a regression coefficient of 0.9996, indicating that the adsorption of lead using CAC is limited by the chemisorption process.

Synthesis of Plant-Mediated Iron Oxide Nanoparticles and Optimization of Chemically Modified Activated Carbon Adsorbents for Removal of As, Pb, and Cd Ions from Wastewater.

This research study was designed with the aim to prepare plant extract-mediated iron oxide nanoparticles (IONPs) and different chemically modified carbon adsorbents from the Parthenium hysterophorus plant and then optimize the carbon adsorbents by evaluating their adsorption applications in wastewater for the selected metal ions like arsenic (As3+), lead (Pb2+), and cadmium (Cd2+). The Fourier transform infrared spectroscopy (FTIR) technique was used to highlight functional groups in plant-mediated IONPs and chemically modified carbon adsorbents. A scanning electron microscopy study was conducted to explain the surface morphology of the adsorbents. Energy-dispersive X-rays was used for elemental analysis and X-ray diffraction for particle size and crystallinity of the adsorbents. From the study, it was found that the best optimum conditions were pH = 5-6, initial concentration of adsorbate of 10 mg/L, dose of adsorbent of 0.01 g, contact time of 90-120 min of adsorbent and adsorbate, and temperature of 25 °C. At optimum conditions, the adsorption capacities of IONPs for arsenic (As) 144.7 mg/g, lead (Pb) 128.01 mg/g, and cadmium (Cd) ions 122.1 mg/g were recorded. The activated carbon at optimum conditions showed adsorption capacities of 46.35 mg/g for As, 121.95 mg/g for Pb, and 113.25 mg/g for Cd ion. At equilibrium, Langmuir, Freundlich Temkin, and Dubinin-Radushkevich isotherms were applied on the experimental adsorption data having the best R2 values (0.973-0.999) by the Langmuir isotherm. High-correlation coefficient R2 values (0.996-0.999) were obtained from the pseudo-second-order for all cases, showing that the adsorption process proceeds through pseudo second-order kinetics. The apparent adsorption energy E value was in the range of 0.24-2.36 kJ/mol. The adsorption capacity of regenerated IONPs for As gradually decreased from 144.8 to 45.67 mg/g, for lead 128.15 to 41.65 mg/g, and cadmium from 122.10 to 31.20 mg/g in 5 consecutive cycles. The study showed that the synthesized IONPs and acid-activated carbon adsorbent were successfully used to remove selected metal ions from wastewater.

Taguchi’s optimization technique for water deflouridation through electrocoagulation

Excess fluoride in drinking water is posing serious health concern to humankind. Electrocoagulation is an emerging technique for water defluoridation, and recent research is focused on the optimization of process variables for achieving maximum fluoride removal. As such, the Taguchi optimization technique is adopted to arrive at optimum values process parameters which can provide maximum fluoride removal with more accuracy and fewer experimental runs. In the present research a laboratory-scale batch EC reactor with four aluminum electrodes (98% pure) connected to a DC supply for a wide range of fluoride concentrations which were not studied in earlier researches. Taguchi’s L 16 orthogonal array was applied for optimization of the process variable It revealed maximum efficiency of 86.67% for defluoridation at optimum conditions of process variables with pH: 6 ± 0.1, initial adsorbate concentration: 5 mg/L, EC time: 45 min, voltage: 25 V, and IED: 2 cm. The percentage contribution of process variables was obtained by ANOVA in descending order as initial adsorbate concentration (45.31%) > pH (33.83%) > voltage (13.68%) > EC time (4.2%) > IED (2.98%). Freundlich isotherm and second-order kinetic models were found to be the best suitable for water defluoridation using the EC process. FTIR and XRD analysis for EC sludge also confirmed the fluoride sorption onto A l ( O H ) 3 flocs. The electrode consumption of 0.263 kg/ m 3 , and total operational cost of USD 0.6004/ m 3 were estimated for water defluoridation using the EC process.