Sorption of phenol and 4-chlorophenol onto pumice treated with cationic surfactant

4-Chlorophenol adsorption from water solutions by activated carbon functionalized with amine groups: response surface method and artificial neural networks

4-Chlorophenol pollution is a significant environmental concern. In this study, powdered activated carbon modified with amine groups is synthesized and investigated its efficiency in removing 4-chlorophenols from aqueous environments. Response surface methodology (RSM) and central composite design (CCD) were used to investigate the effect of different parameters, including pH, contact time, adsorbent dosage, and initial 4-chlorophenol concentration, on 4-chlorophenol removal efficiency. The RSM-CCD approach was implemented in R software to design and analyze the experiments. The statistical analysis of variance (ANOVA) was used to describe the roles of effecting parameters on response. Isotherm and kinetic studies were done with three Langmuir, Freundlich, and Temkin isotherm models and four pseudo-first-order, pseudo-second-order, Elovich, and intraparticle kinetic models in both linear and non-linear forms. The synthesized adsorbent was characterized using X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analyses. The results showed that the synthesized modified activated carbon had a maximum adsorption capacity of 316.1 mg/g and exhibited high efficiency in removing 4-chlorophenols. The optimal conditions for the highest removal efficiency were an adsorbent dosage of 0.55 g/L, contact time of 35 min, initial concentration of 4-chlorophenol of 110 mg/L, and pH of 3. The thermodynamic study indicated that the adsorption process was exothermic and spontaneous. The synthesized adsorbent also showed excellent reusability even after five successive cycles. These findings demonstrate the potential of modified activated carbon as an effective method for removing 4-chlorophenols from aqueous environments and contributing to developing sustainable and efficient water treatment technologies.

Methylene blue removal using raw and modified biomass Plumeria alba (white frangipani) in batch mode: isotherm, kinetics, and thermodynamic studies

Hazardous dyes used in textile industries are considered high-risk pollutants to the environment. The raw as well as acid-treated Plumeria alba (white frangipani) leaf powder (WFLP and SWFLP) were used for the adsorption of methylene blue (MB) that is available in industrial wastewaters following the batch adsorption technique. The characterizations of adsorbents were done by FTIR, SEM, EDX, TGA, and zeta potential parameters. The adsorption was considered for the effects of temperature, initial dye concentration, solution pH, adsorbent dosage, and contact time. The experimental results obtained in the adsorption of MB were examined by nonlinear error functions like chi-square (χ²), ARE, and MPSD for three isotherm models: Langmuir, Freundlich, and Temkin. The maximum monolayer adsorption capacity, q_max (mg/g), was 45.45 mg/g for raw WFLP and 250 mg/g for SWFLP. The adsorbents fitted to the pseudo-second-order kinetic model (R² = 0.99) using the experimental data of batch adsorption. The thermodynamic studies explained the spontaneity and nature of adsorption for raw and acid-treated adsorbents. The batch experimental results and characterizations of the adsorbents revealed that the selected adsorbents would be the best adsorbents for the removal of MB from the wastewater solution.

Fly ash-, foundry sand-, clay-, and pumice-based metal oxide nanocomposites as green photocatalysts

Metal oxides possess exceptional physicochemical properties which make them ideal materials for critical photocatalytic applications. However, of major interest, their photocatalytic applications are hampered by several drawbacks, consisting of prompt charge recombination of charge carriers, low surface area, inactive under visible light, and inefficient as well as expensive post-treatment recovery. The immobilization of metal oxide semiconductors on materials possessing high binding strength eliminates the impractical and costly recovery of spent catalysts in large-scale operations. Notably, the synthesis of green material (ash, clay, foundry sand, and pumice)-based metal oxides could provide a synergistic effect of the superior adsorption capacity of supporting materials and the photocatalytic activity of metal oxides. This phenomenon significantly improves the overall degradation efficiency of emerging pollutants. Inspired by the novel concept of "treating waste with waste", this contribution highlights recent advances in the utilization of natural material (clay mineral and pumice)- and waste material (ash and foundry sand)-based metal oxide nanocomposites for photodegradation of various pollutants. First, principles, mechanism, challenges towards using metal oxide as photocatalysts, and immobilization techniques are systematically summarized. Then, sources, classifications, properties, and chemical composition of green materials are briefly described. Recent advances in the utilization of green materials-based metal oxide composites for the photodegradation of various pollutants are highlighted. Finally, in the further development of green materials-derived photocatalysts, we underlined the current gaps that are worthy of deeper research in the future.

Evaluation and comparison of aluminum-coated pumice and zeolite in arsenic removal from water resources

In this research the potential of aluminum-coated pumice and zeolite in arsenic, As (V) removal was investigated and compared. Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and X-Ray Flaorescence Spectrometry (XRF) were carried out to determine the properties of the adsorbents. Several parameters including adsorbent dosage] pH, contact time, and initial As(V) concentration were studied. The optimum pH obtained for both adsorbents was pH = 7. As(V) adsorption by both adsorbents followed the Freundlich isotherm (for aluminum-coated pumice and zeolite respectively with R² > 0.98 and R² > 0.99). The obtained data from kinetics showed that the pseudo-second order model could better explain As(V) adsorption for both aluminum-coated pumice and zeolite (R² > 0.98 and R² > 0.99 respectively). Because of low cost, both adsorbents may be economically used, but aluminum-coated zeolite showed high efficiency of, due to its porosity and surface area. More than 96% of As(V) with initial concentration of 250 μg/L was removed by 10 g/L aluminum-coated zeolite at pH = 7 and in 60 minutes to achieve As(V) concentration of 10 μg/L, while only 71% of As(V) could be removed by aluminum-coated pumice.

The investigation of kinetic and isotherm of fluoride adsorption onto functionalize pumice stone

In this research work, pumice that is functionalized by the cationic surfactant, hexadecyltrimethyl ammonium (HDTMA), is used as an adsorbent for the removal of fluoride from drinking water. This work was carried out in two parts. The effects of HDTMA loading, pH (3-10), reaction time (5-60 min) and the adsorbent dosage (0.15-2.5 g L(-1)) were investigated on the removal of fluoride as a target contaminate from water through the design of different experimental sets in the first part. The results from this first part revealed that surfactant-modified pumice (SMP) exhibited the best performance at dose 0.5 g L(-1), pH 6, and it adsorbs over 96% of fluoride from a solution containing 10 mg L(-1) fluoride after 30 min of mixing time. The four linear forms of the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms model were applied to determine the best fit of equilibrium expressions. Apart from the regression coefficient (R(2)), four error functions were used to validate the isotherm and kinetics data. The experimental adsorption isotherm complies with Langmuir equation model type 1. The maximum amount of adsorption (Q(max)) was 41 mg g(-1). The kinetic studies indicated that the adsorption of fluoride best fitted with the pseudo-second-order kinetic type 1. Thermodynamic parameters evaluation of fluoride adsorption on SMP showed that the adsorption process under the selected conditions was spontaneous and endothermic. The suitability of SMP in defluoridation at field condition was investigated with natural groundwater samples collected from a nearby fluoride endemic area in the second part of this study. Based on this study's results, SMP was shown to be an affordable and a promising option for the removal of fluoride in drinking water.

Efficient removal of phenol from water using Fe(2)O(3) semiconductor catalyst under UV laser irradiation

Efficient removal of phenol was carried out using laser induced photocatalyis process in the presence of Fe(2)O(3) semiconductor catalysts, and under UV laser irradiation. Parametric dependence of the removal process was investigated carefully by variation of laser irradiation time, laser energy, and concentration of the catalysts. pH measurements were also carried out to understand the photocatalytic process for removal of phenol. Maximum phenol removal achieved in this process was more than 90% during 1 hour of laser irradiation. This is considered highly efficient as compared to conventional setups using lamps. Reaction kinetics for the removal of phenol was also studied, and a reaction rate of 0.017 min(- 1) was estimated, following first order kinetics.

Cadmium adsorption on vermiculite, zeolite and pumice: batch experimental studies

Batch experiments were performed to evaluate the combined effects of ionic activity, pH, and contact time on the cadmium sorption in three different minerals, vermiculite, zeolite, and pumice, commonly employed as substrata in nurseries and recently considered for their potential use in remediation methods. The extent of cadmium sorption was vermiculite>zeolite>pumice, as shown by the Langmuir and Freundlich parameters, and it was highly dependent on mineral characteristics. The percentage of cadmium sorption in zeolite and vermiculite did not depend on cadmium concentration, while in pumice this percentage was positively correlated to the initial cadmium concentration. At low cadmium concentrations (30-120 microM), the metal sorbed on zeolite was mainly present in the nonexchangeable form (70%) at levels much higher than those found for vermiculite and pumice. The primary variable responsible for determination of cadmium mobility in these minerals was confirmed to be pH. The ionic concentrations of Hoagland nutrient solution were significantly modified by both pH and mineral composition, while the presence of cadmium caused no changes. With vermiculite and zeolite, the time-course of cadmium sorption was related to mineral composition to a greater extent than to cadmium concentration. While with pumice, the percentage of cadmium sorbed after 6 weeks was lower than with the other two minerals, and it was inversely correlated to the initial cadmium concentration.

Adsorption of phenolic compounds on low-cost adsorbents: A review

Adsorption techniques are widely used to remove certain classes of pollutants from wastewater. Phenolic compounds represent one of the problematic groups. Although commercial activated carbon is a preferred adsorbent for phenol removal, its widespread use is restricted due to the high cost. As such, alternative non-conventional adsorbents have been investigated. The natural materials, waste materials from industry and agriculture and bioadsorbents can be employed as inexpensive adsorbents. The review (i) presents a critical analysis of these materials; (ii) describes their characteristics, advantages and limitations; and (iii) discusses the various mechanisms involved. There are several issues and drawbacks concerned on the adsorption of phenolic compounds that have been discussed in this review article. It is evident from the review that low-cost adsorbents have demonstrated high removal capabilities for certain phenolic compounds. In particular, industrial waste might be a promising adsorbent for environmental and purification purposes.

Effects of preparation and experimental conditions on removal of phenol by surfactant-modified zeolites

The removal of phenol from aqueous solutions using surfactant-modified clinoptilolite-rich tuffs (SMZ) prepared from two Mexican zeolitic tuffs (Chihuahua and Oaxaca) was investigated. Sodium homoionization of the zeolitic rocks was performed before they were modified with the surfactants: hexadecyltrimethylammonium chloride or bromide and bencylcetildimethylammonium chloride. The surfactants in the modified zeolitic materials were determined considering the total carbon in the samples. The phenol removal was determined in a batch system taking into consideration the different quantities of surfactants in the zeolitic tuffs, contact time, pH and initial phenol concentration. The phenol was determined in the aqueous solutions by UV/Vis spectroscopy. Results showed that the formation of a hemimicelle or admicelle on the zeolites depended on the initial surfactant concentration and they were responsible for the type of interactions between the phenol and the surfactant-modified zeolites. Phenol adsorption by the surfactant-modified zeolites was carried out in approximately three hours. Phenol adsorption data was best adjusted to the pseudo-second order kinetic model. Both, surface properties of the surfactant-modified zeolites and pH of solution play an important role in the removal of this pollutant from aqueous solutions and they are responsible for the type of mechanism involved.

Adsorption of nutrients and cadmium by different minerals: experimental studies and modelling

This work analyses cadmium sorption by natural vermiculite, zeolite, and pumice, which have been recently considered for their potential use in remediation of contaminated soils. Batch experiments were performed to investigate the interactions between the mineral surfaces and the main nutritive cations of Hoagland solution. In addition to their ameliorative effect of reducing metal mobility, these minerals are able to interact to different extents with various components of the nutrient solution and can change the availability of essential nutrients in solution. Therefore, the minerals were also exposed to a range of cadmium doses to compare their different affinities for this element and to analyse the cadmium-nutrient interactions. The results showed that the nutrient solution composition was significantly modified by contact with zeolite and vermiculite, and to a minor extent with pumice. The ionic equilibrium between the solid and aqueous phases was attained at several time points depending on the cation. Ammonium and potassium ions were almost entirely absorbed by zeolite, while in vermiculite endogenous magnesium ions were exchanged with the liquid phase calcium ions. The amount of cadmium adsorbed on mineral surfaces equilibrated with the nutrient solution showed the following sequence zeolite>vermiculite>pumice, and the cation concentrations of the fluid phase were sensitive to cadmium addition.

Adsorption of 4-chlorophenol from aqueous solutions by xad-4 resin: isotherm, kinetic, and thermodynamic analysis

Removal of 4-chlorophenol (4-CP) from synthetic aqueous solutions through adsorption on Amberlite XAD-4 resin, a non-ionic macroreticular resins, under batch equilibrium experimental conditions at 298, 308 and 318K was investigated. It is necessary to propose a suitable model to a better understanding on the mechanism of 4-CP adsorption. For this purpose, Langmiur, Freundlich, Toth, and Redlich-Peterson (RP) isotherm models were compared. The two and three parameters in the adopted adsorption isotherm models were determined by the help of MATLAB package program. It was determined that best fitted adsorption isotherm models were obtained to be in the order: Redlich-Peterson>Langmuir>Toth>Freundlich isotherms. The pseudo-second-order kinetic model provided the best correlation to the experimental results. Results of the intra-particle diffusion model show that the pore diffusion is not the only rate limiting step. The lower correlation of the data to the Bangham's equation also represents that the diffusion of the adsorbate into pores of the sorbent is not the only rate-controlling step. The thermodynamic constants of adsorption phenomena; DeltaG degrees, DeltaH degrees, and DeltaS degrees were found as -4.17 (at 298K) kJ/mol, -42.01 kJ/mol, and -0.127 kJ/(mol K), respectively. The results showed that adsorption of 4-CP on Amberlite XAD-4, a nonionic polymeric resin was exothermic and spontaneous.

Characteristics of phenol and chlorinated phenols sorption onto surfactant-modified bentonite

Surfactant-modified bentonite was synthesized by replacing adsorbed Na+ with long-chain alkyl quaternary ammonium cation, hexadecyltrimethylammonium bromide (HDTMAB). The sorption isotherms of phenol, p-chlorophenol, and 2,4-dichlorophenol were modeled according to the Langmuir and Freundlich equations. The Langmuir isotherm was found to describe the equilibrium adsorption data well. The mechanisms and characteristics of sorption of these ionizable organic contaminants onto surfactant-modified bentonite from water were investigated systematically and described quantitatively. The sorption properties are affected by the treatment conditions, such as amount of organobentonite, and the properties of organic compounds. Results indicated that adsorption of phenols from water was in proportion to their hydrophobicities, which increased with chlorine addition (phenol<p-chlorophenol<2,4-dichlorophenol). Sorption isotherms of these phenols were typically nonlinear. Both adsorption and partition contribute to the sorption of investigated phenols to organobentonite. The separate contributions of adsorption and partition to the total sorption of these compounds to organobentonite is analyzed mathematically. Results indicate that the partition effect is weak and linear with contaminant concentration, whereas the adsorption effect is more powerful and nonlinear with contaminant concentration. The sorption of phenols onto organobentonite was dominated by adsorption at low concentrations and partition started to dominate at high concentrations, making the organobentonites powerful sorbents for organic contaminants over a wide range of concentrations.