Investigation of factors that affect cationic surfactant loading on activated carbon and perchlorate adsorption

Use of Anionic Surfactant-Modified Activated Carbon for Efficient Adsorptive Removal of Crystal Violet Dye

Studies have been carried out to investigate the removal of crystal violet (CV) cationic dye by using rice husk which was used as a raw material to prepare activated carbon (AC) and it was treated with anionic surfactant. In this process, AC was treated with three different anionic surfactants, namely, lauryl sulfate ACMAS, ACSDS, and ACHTAB. Characterization and analysis of optimum ACMAS were done using different techniques which were used which proves the adsorption of the dye by ACMAS. Effects of various physical parameters like time of contact, additive salts, initial dye concentration, effect of pH, and effect of adsorbent dose were studied. Minute changes in the dye removal capacity were observed due to the presence of various cations. Cations like NO2- caused an increase in the capacity of adsorption but cations like Fe2+decreased the capacity of adsorption in the sample solution. The effectiveness of film diffusion and intraparticle has been shown by mass transfer parameters. The various kinetic studies have shown that pseudo second-order kinetic study best suited with the experimental data. Error analysis and studies of isotherms have shown that the adsorption equilibrium was controlled by Langmuir isotherm study with maximum CV dye adsorption capacity of 235.7 mg/g. Thermodynamics studies revealed endothermicity of the process with negative $\Delta G$ values and positive $\Delta S$ and $\Delta H$ values. Activation energy of 48.31 kJ/mol suggested chemisorption process of the system. Column studies were carried out by using different models to study the variation of bed depth, dye concentration, flow rate, etc. Regeneration experiments have given the ability of the adsorbent to be reused. In this present study, it has been noticed that the use of anionic surfactant-treated activated carbon significantly improved the adsorption of dye and this is a process of adsorption in which not much attention has been given for research till date.

In Situ Growth Synthesis of the CNTs@AC Hybrid Material for Efficient Nitrate-Nitrogen Adsorption

Nitrate-nitrogen (NO3-N) is a common pollutant in aquatic environments and causes many environmental issues and health problems. This study successfully applied the activated AC@CNT composite synthesized by CNTs in-situ growth and post-treated by myristyltrimethylammonium bromide (MTAB) for NO3-N adsorption from wastewater. The results show that the highest NO3-N adsorption capacity of AC@CNTs-M was 14.59 mg·g-1. The in-situ growth of CNTs gave a higher specific surface area and more mesoporous volume, while MTAB uniformly occupied part of the pore structure after the modification process. The AC@CNTs-M had more surface functional groups of hydroxyl and carboxyl, which are favorable for the adsorption of NO3-N. The NO3-N adsorption on AC@CNTs-M was best defined by the pseudo-second-order model, and the isothermal analysis shows that NO3-N adsorption is a multiple process with a maximum adsorption capacity of 27.07 mg·g-1. All the results demonstrate the great potential of AC@CNTs-M for NO3-N adsorption from water, especially in acidic wastewater.

Bromate removal from water by acid activated and surfactant enriched Red Mud - the case of cooling water

Red Mud is a hazardous by-product of the Bayer process, used to produce alumina from bauxite, with ability to adsorb anions from water. Acid activation and enrichment with CetylTrimethylAmmonium Chloride (CTAC), a cationic surfactant, are employed to enable it to remove bromate initially from spiked double-distilled water. CTAC enrichment is found to substantially improve Red Mud's bromate removal ability in comparison to acid activation alone. Fourier Transformation Infrared Spectroscopy is used to evaluate the effectiveness of the enrichment process. Maximum CTAC loading is 0.037 g per g acid activated Red Mud (AARM). Adsorption is faster after CTAC enrichment. pH increase is found to adversely affect both AARM and acid activated CTAC enriched Red Mud's (CTAC-AARM) bromate removal capability, yet CTAC-AARM's ability proves more resistant to pH changes. Adsorption data fit best the Langmuir isotherm model for both adsorbers. The R² values for AARM and CTAC-AARM are 0.955 and 0.964 respectively. Maximum adsorbable bromate quantity is almost 2.5 times higher for CTAC-AARM in comparison to AARM. Finally, both Red Mud adsorbers are compared with respect to their ability to remove bromate from cooling water; an industrial matrix rich in competing ions. As cycles of concentration and pH appreciate, bromate adsorption is hindered regardless of the adsorber used. However, CTAC-AARM still performs better in removing bromate. It is proven that after suitable processing, Red Mud can re-enter the industrial cycle by playing a role in bromate removal from industrial waters.

Adsorption of Methylene Blue in Water onto Activated Carbon by Surfactant Modification

In this paper, the enhanced adsorption of methylene blue (MB) dye ion on the activated carbon (AC) modified by three surfactants in aqueous solution was researched. Anionic surfactants—sodium lauryl sulfate (SLS) and sodium dodecyl sulfonate (SDS)—and cationic surfactant—hexadecyl trimethyl ammonium bromide (CTAB)—were used for the modification of AC. This work showed that the adsorption performance of cationic dye by activated carbon modified by anionic surfactants (SLS) was significantly improved, whereas the adsorption performance of cationic dye by activated carbon modified by cationic surfactant (CTAB) was reduced. In addition, the effects of initial MB concentration, AC dosage, pH, reaction time, temperature, real water samples, and additive salts on the adsorption were studied. When Na+, K+, Ca2+, NH4+, and Mg2+ were present in the MB dye solution, the effect of these cations was negligible on the adsorption (<5%). The presence of NO2- improved the adsorption performance significantly, whereas the removal rate of MB was reduced in the presence of competitive cation (Fe2+). It was found that the isotherm data had a good correlation with the Langmuir isotherm through analyzing the experimental data by various models. The dynamics of adsorption were better described by the pseudo-second-order model and the adsorption process was endothermic and spontaneous. The results showed that AC modified by anionic surfactant was effective for the adsorption of MB dye in both modeling water and real water.

Compatibility of Celluloce Nanocrystal Modified Cetrimmonium Chloride (CTAC) in Polylactic Acid Matrix as Packaging Material

Growth of population increases the consumption of nonbiodegradable plastic which causes waste buildup. Diversion of plastic material from nonbiodegradable material to biodegradable is an important alternatif. PLA is a plastic polymer that is easily degraded but very brittle. Palm oil waste containing oil palm empty bunches has the potential as a reinforcement material because the cellulose content is 30-40%. Minimizing size to nanoscale will increase the surface area and dispersion ability of cellulose dispersibility into the PLA polymer matrix, thus increasing compatibility in terms of and mechanical properties and surface morphology of the composite. Hydrolysis by strong acid and centrifugation at 5000 rpm succeeded in making cellulose nanocrystal with index of polidisperse 0.5 and average particle diameter of 7.967 nm. CTAC as a solubilizer and surface modifier agent successfully made interaction to cellulose nanocrystal as confirmed on absorption at wave number 2850 cm-1, 2960 cm-1 and 720 cm-1. Modified At the fixed CTAC concentration of 0.2 mol, the best mechanical properties of CNC-PLA composites were obtained in the composition ratio of 90: 10 with tensile strength of 26.295 MPa, elongation break of 68.18%, and Young modulus of 0.387 Gpa. The greater the CTAC added to nanocrystal cellulose, the lower the reinforcement value and the less reduction. Based on the results of morphology surface characterization, PLA surfaces required for degradation were obtained.

Enhanced surface activity of activated carbon by surfactants synergism

Activated carbon (AC) modification has been intensively studied in order to design carbon electrodes with enhanced electrochemical performance. Hexadecyltrimethylammonium bromide (HDTMA) and Tween 80 were employed for enhancing the surface activity of AC via synergism. The synergistic effects of the mixed surfactants on AC surface activity in the light of interface behaviors were studied. Both field emission scanning electron micrographs and FTIR spectra indicated a successful adsorption of loaded surfactants. AC gained a good wettability originated from the surfactants, especially in the binary mixture (T80-HDTMA). The zeta potential results unveiled the positive charge density enhancement in the mixed surfactants system. Isoelectric point and point of zero charge implicate heterogeneous distribution of charges and the extent of surfactants treatment. Tween 80 displayed a significant size control dependence on AC particles. Electrochemical characterization revealed a higher specific capacitance and a decaying resistance of specific capacitance in AC-T80-HDTMA than AC-HDTMA at high concentration. In 5 g L⁻¹ of NaCl, AC-T80-HDTMA (0.01 : 0.01 mM) exhibits the specific capacitance of 209.79 F g⁻¹, at 0.8 V whereas AC-HDTMA (0.01 mM) and AC exhibited 186.5 F g⁻¹, 178.9 F g⁻¹, respectively. Moreover, the stability testing reveals a strong attachment of HDTMA in AC-T80-HDTMA than AC-HDTMA with the loss of 0.32% and 1.32%, respectively. The hypothetical synergistic mechanism of surfactants adsorption on the surface of AC was depicted as hydrophobic interaction and steric stabilization being the main keys for the synergy between cationic and nonionic surfactants. This study demonstrates the beneficial effects of mixed surfactants on AC electrode properties and discloses the impact on electrochemical performance.

Enhancement of AC surface activity by surfactants synergism for electrochemical applications.

Adsorption of HDTMA-Br surfactant with concentration variation by rice husk-based activated carbon produced by variation of carbonization temperature

Research has been conducted on the adsorption of HDTMA-Br surfactant by rice husk-activated carbon with variation of carbonization temperature and concentration of HDTMA-Br. This study aims to produce surfactant modified activated carbon (SMAC), therefore it is necessary to determine the influence of carbonization temperature to the adsorption capability of activated carbon on HDTMA-Br surfactant by identifying the amount of HDTMA-Br surfactant absorbed, to characterize the characters of carbon, activated carbon and activated carbon adsorbing surfactant using FTIR and SAA. Carbonization was carried out by pyrolysis with temperature variations of 300, 350 and 400°C. The carbon produced was activated using 60% H3PO4 for 1 hour. After that, the activated carbon was applied to adsorb HDTMA-Br surfactant by varying the concentration that were 300, 1100, 1900, 2700, 3500 and 4300 ppm. The results showed that HDTMA-Br adsorbed tended to increase by increasing the concentration of surfactant. In addition, the best carbonization temperature showing high adsorption capability of activated carbon was at 300°C. FTIR spectra of activated carbon showed the presence of P = O peak; at the SMAC sampel there was peak of N-(CH3)3 with different intensities in three samples. Moreover, SAA analysis showed that the surface area of activated carbon increased compared to carbon and slightly decreased after the activated carbon absorbed HDTMA-Br.

Highly Efficient and Sustainable Spent Mushroom Waste Adsorbent Based on Surfactant Modification for the Removal of Toxic Dyes

The treatment of wastewater always demands eco-friendly and cost-efficient adsorbents. In this paper, spent mushroom waste (SMW) was modified by a cationic surfactant (cetyltrimethylammonium bromide, CTAB) to eliminate toxic dyes. A characterization of adsorbents confirmed that CTAB was successfully embedded into the SMW structure. The spent mushroom waste, modified by CTAB (SMWC), exhibited an excellent adsorption capacity of 249.57 mg·g−1, 338.67 mg·g−1, and 265.01 mg·g−1 for the Direct red 5B (DR5B), Direct blue 71 (DB71), and Reactive black (RB5) dyes, respectively. Batch experiments indicated that the dye adsorption of SMWC depended mainly on pH, dye concentration, temperature, and ionic strength. The adsorption isotherm could be fitted to the Langmuir model and described by the pseudo-second-order kinetic model. The dye adsorption mechanism was dominated mostly by the chemosorption of the dyes and the SMWC surface. Thermodynamic parameters showed that the adsorption was endothermic and spontaneous. SMWC could successfully remove over 90% of dyes from various water samples. This can be considered a feasible waste resource utility, since it meets both the ecological and the economic requirements for auspicious industrial applications.

Design and controllable synthesis of ethylenediamine-grafted ion imprinted magnetic polymers for highly selective adsorption to perchlorate

A series of ethylenediamine-grafted ion imprinted magnetic polymers (Fe₃O₄@IIPs) were synthesized via ultrasonic assisted suspension polymerization with perchlorate (ClO₄⁻) as an ion imprinting template. They were characterized by XRD, EA, VSM, FTIR and XPS and applied as adsorbents for ClO₄⁻ removal from aqueous solutions. The effects of the usage amount of crosslinking agent divinylbenzene (DVB) used for preparation on the structure and the adsorptive performance of Fe₃O₄@IIPs were investigated. The results show that the Fe₃O₄@IIPs have an average size of 200–800 nm, which increases with the increase of the amount of DVB from 0 to 2 g during the preparation process. The saturation magnetization intensities are at 35.6–42.8 emu g⁻¹, which decrease with the increase of the usage amount of DVB. The addition of DVB is beneficial to the formation and stability of the ion imprinted cavity of Fe₃O₄@IIPs. The effects of the solution pH value, initial concentration of ClO₄⁻, and adsorption time on the adsorption properties of ClO₄⁻ in aqueous solutions were investigated. The results show that the adsorption capability is affected significantly by solution pH value and reaches the maximum adsorption capacity at pH 3.0. The best adsorption capacity and selectivity of Fe₃O₄@IIPs to ClO₄⁻ can be obtained when the usage amount of DVB is at 0.5 g for synthesis. The adsorption mechanisms might include both ion exchange and electrostatic interaction. The isothermal adsorption curves mainly obey the Langmuir model with the theoretical maximum adsorption capacities (q_m,c) at 76.92–111.1 mg g⁻¹ and the experimental maximum adsorption capacities (q_m,e) at 75.7–108.9 mg g⁻¹, respectively, which are much higher than those of the non-ion imprinted material (Fe₃O₄@NIP, q_m,NIP: q_m,c at 60.61 mg g⁻¹ and q_m,e at 59.0 mg g⁻¹). The adsorption kinetic studies show that the adsorption processes reach equilibrium within 10 min and the kinetic data are well fitted to the pseudo-second-order model. There is almost no interference by the coexisting anions for the selective adsorption of ClO₄⁻, with a imprinting factor (α) at 1.8, and selectivity factor (β) larger than 5.9 for several kinds of common co-existing anions, respectively. The Fe₃O₄@IIPs are ideal candidates for removal of ClO₄⁻ from aqueous solution.

A series of ethylenediamine-grafted ion imprinted magnetic polymers (Fe₃O₄@IIPs) were synthesized via ultrasonic assisted suspension polymerization with perchlorate (ClO₄⁻) as an ion imprinting template.

As-synthesized multi-walled carbon nanotubes for the removal of ionic and non-ionic surfactants

This research deals with the application of untreated multi-walled carbon nanotubes (MWCNT) in their agglomerates form for the removal of non-ionic (TX-100), cationic (CTAB) and anionic (SDBS) surfactants from aqueous media. In order to optimize the removal process, the influence of several key parameters was investigated including contact time under different solid/liquid ratios, initial solution pH, temperature, along with ultrasonication assistance and desorption assays. Experimentations revealed that pH variation enhanced the removal capacities at optimum values of 6, 2 and 8 for TX-100, SDBS and CTAB, respectively, and that hydrophobic interaction is a major adsorption factor, especially for non-ionic surfactant with possible electrostatic interactions occurring for the ionic ones. As well, removal efficiencies peaked for an optimum temperature range between 35 and 45 °C. As for the ultrasonication assistance, it enhanced the overall removal capacities, especially that of the ionic surfactant, with an enhancement of 52% for the case of SDBS after 1h of treatment. The modeling results revealed that the pseudo-second order model provided the best correlation of the dynamic data and that the process was controlled by intraparticle diffusion phenomena. At equilibrium, and under optimized experimental conditions, untreated MWCNTs showed promising removal capacities with 359, 312 and 156 mg/g for TX-100, SDBS and CTAB, respectively.