Search

The complete removal of low concentration organic pollutants from wastewater to obtain clean water has always been a highly desired but challenging issue. In response to this, we proposed a new strategy to fabricate a carbon-in-silicate nanohybrid composite by recycling dye-loaded layered clay adsorbent and converting them to new heterogeneous carbon-in-silicate nanocomposite through an associated calcination-hydrothermal activation process. It has been confirmed that most of the dye molecules were present in waste rectorite adsorbent using an intercalation mode, which can be in situ converted to carbon in the confined interlayer spacing of rectorite. The further hydrothermal activation process may further improve the pore structure and increase surface active sites. As expected, the optimal composite shows extremely high removal rates of 99.6% and 99.5% for Methylene blue (MB) and Basic Red 14 (BR) at low concentrations (25 mg/L), respectively. In addition, the composite adsorbent also shows high removal capacity for single-component and two-component dyes in deionized water and actual water (i.e., Yellow River water, Yangtze River water, and seawater) with a removal rate higher than 99%. The adsorbent has good reusability, and the adsorption efficiency is still above 93% after five regeneration cycles. The waste clay adsorbent-derived composite adsorbent can be used as an inexpensive material for the decontamination of dyed wastewater. [ABSTRACT FROM AUTHOR]

In this study, the novel pH‐sensitive s‐IPN consist of sodium alginate integrated with poly(HEMA‐co‐MA) hydrogel matrix are prepared by using two‐step methodology. In the first step, 2‐hydroxyethyl methacrylate (HEMA)/maleic acid (MA) copolymeric hydrogels are prepared by gamma radiation polymerization. Then, poly(HEMA‐co‐MA) hydrogel was immersed in sodium alginate solution (SA) and finally gamma radiation polymerization was carried out. The swelling, pH‐sensivity and diffusion properties of the prepared s‐IPN gels in deionized water and in dye solutions were investigated. Methylene Blue (MB) was used as a model dye. MB adsorption capacities of the hydrogels were found to be 0.26, 0.40 and 13.77 mg MB/g dry gel in PHEMA, P(HEMA‐co‐MA) and s‐IPN SA/P(HEMA‐co‐MA) hydrogels, respectively. MB release data was fitted to various kinetic models to study the dye release behavior. The MB release from all the prepared hydrogels fitted the Korsmeyer‐Peppas model. Swelling, diffusion and MB adsorption properties of the new s‐IPN hydrogel were improved with the inclusion of SA and MA in the gel structure. [ABSTRACT FROM AUTHOR]

Methylene blue dye can cause damage to the eyes of humans and animals, as well as skin irritation. Also, it can result in nausea, cancer, vomiting, convulsions, and diarrhea. Consequently, in this work, an aqueous solution of sodium metasilicate pentahydrate (12 g dissolved in 50 mL of deionized water) reacted separately with two aqueous solutions of magnesium nitrate hexahydrate (8.47 g dissolved in 50 mL of deionized water and 11.47 g dissolved in 50 mL of deionized water) to obtain sodium magnesium silicate hydrate/sodium magnesium silicate hydroxide as novel nanostructures via the sol–gel method. Besides, the synthesized nanostructures were utilized for the efficient removal of methylene blue dye from aqueous media. The mean crystallite sizes of the nanostructures, which were synthesized using 8.47 and 11.47 g of magnesium nitrate hexahydrate, are 73.17 and 60.25 nm, respectively. The nanostructures, which were synthesized using 8.47 and 11.47 g of magnesium nitrate hexahydrate, were composed of cubes, spheres, and irregular shapes with mean grain sizes of 175 and 110 nm, respectively. The BET surface areas of the nanostructures, which were synthesized using 8.47 and 11.47 g of magnesium nitrate hexahydrate, are 171.04 and 189.90 m2/g, respectively. The maximum adsorption capacities of the nanostructures, which were synthesized using 8.47 and 11.47 g of magnesium nitrate hexahydrate, toward methylene blue dye are 384.62 and 404.86 mg/g, respectively. The adsorption of methylene blue dye using the synthesized nanostructures is consistent with the pseudo-second-order kinetic model and the Langmuir equilibrium isotherm. Also, the adsorption of the methylene blue dye is chemical and exothermic. [ABSTRACT FROM AUTHOR]

The efficiency of saturated Activated Carbon (AC) electrochemical regeneration was evaluated. Reactor configurations in cathodic/anodic process, applied current effect on the properties of AC and Methylene Blue MB-AC interactions and adsorption/desorption mechanisms were studied. The efficiency was measured by adsorption capacity adsorption/regeneration cycles and changes in the adsorbent characteristic were analyzed through FTIR, BET, Optical Microscopy (OM) and SEM before and after the regeneration. The energy consumption was analyzed to assess the economic feasibility. It was found that the electrochemical treatment was efficient in returning the AC adsorption capacity, maximum efficiencies of approximately 79% and 84% were reached when the Carbon Fiber Cloth-AC electrode was subjected to anodic and cathodic currents, respectively, at a current of 0.1 A. In addition, the material demonstrated good stability through adsorption-regeneration cycles by cathodic process, with the material's adsorption capacity being almost totally recovered for 8 consecutive cycles. The removal percentage around 80% was kept after the cycles, with optimal conditions when the electrode was subjected to cathodic currents, NaCI as electrolyte at a current of 0.1 A for 2 h. The characterization techniques provided results that allow to explain the higher and prolonged efficiency of the cathodic current. Furthermore, these reactor configurations achieved an electrical energy consumption of 2.3 and 2.1 kWh kg-1 of material for cathodic and anodic, respectively. These results indicate that the electrochemical is an economical and environmental suitable technique capable of restore carbon adsorbents to be reusable for several water treatment cycles. [ABSTRACT FROM AUTHOR]

Low-cost adsorbents from cassava leaves (CLP) were prepared by simply washing the leaf powder with deionized water. The adsorption of methylene blue (MB) from the aqueous solution was measured in order to examine the adsorbent performance. The effect of the pH of the solution was studied by varying pH from 2 to 10. The kinetics of MB adsorption onto CLP followed the pseudo-second-order kinetic model with a k-value of 0.087907 g mg-1 min-1 and 0.094081 g mg-1 min-1 for CLP before and after washing, respectively. The adsorption isotherm for both adsorbents followed the Langmuir isotherm model with qm values of 178.5 mg g-1 and 243.9 mg g-1. The existence of disturber ions was investigated by adding NaCl into the MB solutions at a variety of concentrations. [ABSTRACT FROM AUTHOR]

Polysaccharide-based hydrogel adsorbents become popular because of their high adsorption capacity and fast adsorption rate, but their low removal rate and poor pH resistance have always been fatal shortcomings. Herein, a feasible strategy was proposed to strengthen the ability of hydrogel adsorbent to remove organic pollutants (i.e., dye) by incorporating natural rectorite (REC) into chitosan- g -poly (2-acrylamido-2-methyl-propane-sulfonic-acid) hydrogel network to form a rectorite-in-polymer network structure. The introduction of less dosage of REC (1.2 wt%) into the hydrogel facilitates to improve its adsorption capacities toward methylene blue (MB) in deionized water, tap water, seawater, Yangtze River water, and Yellow River water (1083.39–1303.49 mg/g); while incorporating higher content of REC (15.8 wt% REC) helps to improve the removal rate (99.6% for MB in real waters), which are greatly superior to commercial activated carbons. The adsorbent keeps high adsorption efficiency in a broad pH range (2–11), and can be reused for >4 times. [Display omitted] • Synthesized chitosan-based hydrogel has a rectorite-in-polymer composite network. • The hydrogel shows high adsorption capacity (1303.49 mg/g) and removal rate (99.6 %). • Removal efficiency keeps high in real waters (Yangtze River, Yellow River, seawater). • The hydrogel's adsorption capacity far exceeds that of commercial activated carbon. • This method is universal to enhance the removal efficiency of hydrogel adsorbent. [ABSTRACT FROM AUTHOR]