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Multi-functionalized fibrous silica KCC-1 (MF-KCC-1) bearing amine, tetrasulfide, and thiol groups was synthesized via a post-functionalization method and fully characterized by several methods such as FTIR, FESEM, EDX-Mapping, TEM, and N2 adsorption–desorption techniques. Due to abundant surface functional groups, accessible active adsorption sites, high surface area (572 m2 g−1), large pore volume (0.98 cm3 g−1), and unique fibrous structure, mesoporous MF-KCC-1 was used as a potential adsorbent for the uptake of acid fuchsine (AF) and acid orange II (AO) from water. Different adsorption factors such as pH of the dye solution, the amount of adsorbent, initial dye concentration, and contact time, affecting the uptake process were optimized and isotherm and kinetic studies were conducted to find the possible mechanism involved in the process. For both AF and AO dyes, the Langmuir isotherm model and the PFO kinetic model show the most agreement with the experimental data. According to the Langmuir isotherm, the calculated maximum adsorption capacity for AF and AO were found to be 574.5 mg g−1 and 605.9 mg g−1, respectively, surpassing most adsorption capacities reported until now which is indicative of the high potential of mesoporous MF-KCC-1 as an adsorbent for removal applications. [ABSTRACT FROM AUTHOR]

To date, many nanoadsorbents have been developed and used to eliminate heavy metal contamination, however, one of the challenges ahead is the preparation of adsorbents from processes in which toxic organic solvents are used in the least possible amount. Herein, we have developed a new carboxylic acid-functionalized layered double hydroxide/metal–organic framework nanocomposite (LDH/MOF NC) using a simple, effective, and green in situ method. UiO-66-(Zr)-(COOH)2 MOF nanocrystals were grown uniformly over the whole surface of COOH-functionalized Ni50Co50-LDH ultrathin nanosheets in a green water system under a normal solvothermal condition at 100 °C. The synthesized LDH/MOF NC was used as a potential adsorbent for removal of toxic Cd(II) and Pb(II) from water and the influence of important factors on the adsorption process was monitored. Various non-linear isotherm and kinetic models were used to find plausible mechanisms involved in the adsorption, and it was found that the Langmuir and pseudo-first-order models show the best agreement with isotherm and kinetic data, respectively. The calculated maximum adsorption capacities of Cd(II) and Pb(II) by the LDH/MOF NC were found to be 415.3 and 301.4 mg g−1, respectively, based on the Langmuir model (pH = 5.0, adsorbent dose = 0.02 g, solution volume = 20 mL, contact time = 120 min, temperature = 25 ℃, shaking speed 200 rpm). [ABSTRACT FROM AUTHOR]

Oxidized activated carbon (OAC) was prepared from a waste mixture containing palm stem, paper, and plastic and used for the removal of Co(II) from aqueous medium. Adsorption was studied as a function of OAC dose (0.03-0.1 g), time (10-180 min), pH (2-6) and initial Co(II) concentration (50 mg L-1). The maximum adsorption capacity was found 83.6 mg g-1 at pH 4. The adsorption process followed the Freundlich isotherm model and pseudo-second-order kinetics. The OAC showed better efficiency comparable with other reported adsorbents. The results suggested that the prepared OAC could be used as a cost-effective adsorbent for the Co(II) removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

In this study, the potential of natural pumice (NP) and iron-coated pumice stone (Fe-CP) as novel low-cost adsorbents to remove ethidium bromide (EtBr) from aqueous solutions was investigated. The operational parameters affecting removal efficiency and adsorption capacity such as adsorbent dose, initial EtBr concentration, pH, and contact time were studied in order to maximize EtBr removal. The maximum amount of adsorbed EtBr (qm) using NP and Fe-CP was 40.25 and 45.08 mg g‒1, respectively. It was found that EtBr adsorption followed the Freundlich isotherm model and fitted the pseudo-second-order kinetics equation for both adsorbents. In addition, the experimental system could be easily modeled by artificial neural network calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eco-design of a highly efficient Cr(VI) adsorbent with bimodal micro-/mesoporous structure. • Green synthesis approach utilizing Sorghum waste as a sustainable silica source for the adsorbent. • A one-pot synthesis method led to homogeneously distributed adsorption sites on the MI-Cl-FDU-12. • MI-Cl-FDU-12 demonstrated a high adsorption capacity of 416.9 mg g-1 at 313 K for Cr(VI) • MI-Cl-FDU-12 adsorbent revealed excellent regeneration performance by six consecutive cycles. This paper presents an eco-design approach to the synthesis of a highly efficient Cr(VI) adsorbent, utilizing a positively charged surface mesoporous FDU-12 material (designated as MI-Cl-FDU-12) for the first time. The MI-Cl-FDU-12 anion-exchange adsorbent was synthesized via a facile one-pot synthesis approach using sodium silicate extracted from sorghum waste as a green silica source, 1-methyl-3-(triethoxysilylpropyl) imidazolium chloride as a functionalization agent, triblock copolymer F127 as a templating or pore-directing agent, trimethyl benzene as a swelling agent, KCl as an additive, and water as a solvent. The synthesis method offers a sustainable and environmentally friendly approach to the production of a so-called "green" adsorbent with a bimodal micro-/mesoporous structure and a high surface area comparable with the previous reports regarding FDU-12 synthesis. MI-Cl-FDU-12 was applied as an anion exchanger for the adsorption of toxic Cr(VI) oxyanions from aqueous media and various kinetic and isotherm models were fitted to experimental data to propose the adsorption behavior of Cr(VI) on the adsorbent. Langmuir model revealed the best fit to the experimental data at four different temperatures, indicating a homogeneous surface site affinity. The theoretical maximum adsorption capacities of the adsorbent were found to be 363.5, 385.5, 409.0, and 416.9 mg g−1 at 298, 303, 308, and 313 K, respectively; at optimal conditions (pH=2, adsorbent dose=3.0 mg, and contact time of 30 min), surpassing that of most previously reported Cr(VI) adsorbents in the literature. A regeneration study revealed that this adsorbent possesses outstanding performance even after six consecutive recycling. [ABSTRACT FROM AUTHOR]

• Olive stone and Date pit upcyled into improved biosorbent material for Cr(VI) removal. • DETA and epichlorohydrin used to introduce amine groups onto DP and OS. • Cr(VI) removed from aqueous solutions via reduction and adsorption mechanism. • New materials have superior removal capacity in compared to other materials. Chemically modified date pit (CM-DP) and olive stone (CM-OS) were studied for their biosorption capacity for hexavalent chromium (Cr(VI)) removal in the aqueous phase. The effect of changing the process conditions, such as the initial Cr (VI) concentration, pH, biosorbent dosage, ionic strength, presence of other ions and temperature were investigated. It showed that at pH = 2, biosorbent dosage >4 g/L and a low ionic strength, both biosorbents showed best biosorption capacity of the Cr(VI) removal. Various isotherm models were applied to fit the experimental data and the Freundlich isotherm model was the best fitting isotherm model for the biosorption experimental data of both biosorbents. The maximum biosorption capacities of CM-DP and CM-OS were found to be 82.63 and 53.31 mg/g respectively, which is comparable to other materials. In the kinetic study, the pseudo second order model can best describe the biosorption process of both biosorbents and the intraparticle diffusion was not the rate-limiting step indicating the contribution of film diffusion in the Cr(VI) removal processes. [ABSTRACT FROM AUTHOR]

Limestone and coffee waste were used during the wet co-granulation process for the production of efficient adsorbents to be used in the removal of anionic and cationic dyes. The adsorbents were characterized using different analytical techniques such as XRD, SEM, FTIR, organic elemental analysis, the nitrogen adsorption method, with wettability, strength and adsorption tests. The adsorption capacity of granules was determined by removal of methylene blue (MB) and orange II (OR) from single and mixed solutions. In the mixed solution, co-granules removed 100% of MB and 85% of OR. The equilibria were established after 6 and 480 h for MB and OR, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1-Methylimidazolium/tetrasulfide/amine-multifunctionalized KCC-1 was synthesized. • This material was used as an adsorbent for acid orange II and acid fuchsin removal. • This adsorbent has a high surface area (555 m2 g−1) and pore volume (0.94 cm3 g−1) • This adsorbent has a high uptake capacity and a low adsorption time for the dyes. In the last few decades, the adsorption technique has attracted tremendous attention as a promising methodology for removing toxic dye pollutants from aquatic environments. Nanoporous adsorbents are one of the most popular adsorbents for dye removal. With comparing two different adsorbents, two important factors, namely adsorption capacity and adsorption time are of particular importance; the higher the adsorption capacity and the shorter the adsorption time, the better and more effective is the adsorption performance. In this paper, a multifunctionalized micro-mesoporous nano-silica KCC-1 (MF-KCC-1) adsorbent bearing 1-methylimidazolium/tetrasulfide/amine groups is synthesized by a simple post-functionalization of the pure KCC-1 for adsorption of acid orange II (AO) and acid fuchsin (AF) from water. In order to investigate the feasible mechanisms involved in the adsorption process, isotherm and kinetic studies were conducted. Among the various isotherm and kinetic models, the Langmuir isotherm and pseudo-first-order kinetic models showed the best agreement with the experimental data. The MF-KCC-1 showed a high adsorption capacity (676.7 and 621.3 mg g−1 for AO and AF) and a short adsorption time (20 min) under constant conditions (pH=3.0, adsorbent dose=0.100 g L–1, solution volume=30 mL, temperature=298 K, shaking speed=180 rpm). The results obtained in this study reveal the positive effect of surface functional groups on the adsorption performance of MF-KCC-1 as a promising nanoadsorbent. [ABSTRACT FROM AUTHOR]