Adsorption properties of cellulose/guar gum/biochar composite hydrogel for Cu2+, Co2+ and methylene blue.

Herein, Typha angustifolia was used as a charcoal source and chemically modified with a strong oxidizing agent, potassium permanganate (KMnO4), to obtain modified Typha angustifolia (MTC). Then, the green, stable and efficient CMC/GG/MTC composite hydrogel was successfully prepared by compounding MTC with carboxymethyl cellulose (CMC) and guar gum (GG) by free radical polymerization. Various variables that influence adsorption performance were explored, and optimal adsorption conditions were determined. The maximum adsorption capacity calculated from the Langmuir isotherm model was 805.45, 772.52, and 598.28 mg g-1 for Cu2+, Co2+, and methylene blue (MB), respectively. The XPS results revealed that the main mechanism of removing pollutants by adsorbent is surface complexation and electrostatic attraction. After five adsorption-desorption cycles, the CMC/GG/MTC adsorbent still exhibited good adsorption and regeneration capacity. This study provides a low-cost, effective and simple method for preparation of hydrogels from modified biochar, which has excellent application potential in the removal of heavy metal ions and organic cationic dye contaminants from wastewater.

Preparation of modified reed carbon composite hydrogels for trapping Cu2+, Ni2+ and methylene blue in aqueous solutions.

The pollution of heavy metal ions and organic dyes seriously endangers human health and causes acute environmental problems. The adsorption method is extensively adopted in the treatment of water pollution which is more harmful to human health. In this work, the original reed carbon (ORC) was functionalized by polyethyleneimine (PEI). By means of radical polymerization, PEI-modified reed carbon (PRC), sodium alginate and lysine were made into carbon-composite acrylic hydrogel (SA/LS/PRC). Meanwhile, SEM, FTIR, TGA, and Zeta potential were used to characterize the adsorbent. The elimination capacity of SA/LS/PRC for Cu2+, Ni2+, and Methylene blue (MB) was researched through batch adsorption experiments. The adsorption behavior of SA/LS/PRC is more suitable for the pseudo-second-order kinetic model of chemical removal of pollutants and the Langmuir model relying on monolayer adsorption. The maximum adsorption capacities of SA/LS/PRC for Cu2+, Ni2+ and MB are 1245.27, 1239.47 and 627.29 mg g-1, respectively, and the adsorption performance is better than those reported in most literatures. The interaction of Cu2+, Ni2+, and MB were studied via binary mixed adsorption experience. Surface complexation and electrostatic interactions are the major removal mechanisms for contaminants. The adsorption capacity of SA/LS/PRC kept above 81% after five cycles. The SA/LS/PRC green hydrogel can be effectively applied in the mixed adsorption process of heavy metal ions and the removal of dyes.

Chitosan-based composite microspheres for treatment of hexavalent chromium and EBBR from aqueous solution.

Hexavalent chromium is widely used in industrial fields, but its pollution has posed a great threat to the environment due to its high toxicity. We created a chitosan-based microsphere biosorbent (CP) by combining polyethyleneimine with chitosan adopting inverse emulsion polymerization method. Under the optimal conditions (pH = 3), the maximum adsorption capacity of composite microspheres can reach 299.89 mg g-1, which is much higher than that of chitosan microspheres (168.91 mg g-1). When the amount of CP is 0.25 g L-1, the removal rate of 50 mg L-1 Cr(VI) and 50 mg L-1 Eriochrome blue-black R (EBBR) can reach 95% and 99%, respectively. The time required for CP to reach adsorption equilibrium (180 min) was significantly shorter than that of chitosan microspheres (540 min), and the adsorption rate was significantly improved. Langmuir isotherm model, pseudo-second-order kinetic model and thermodynamic calculation results penetrated an endothermic spontaneous, monolayer, and chemical adsorption process. Biomass composite microspheres CP has obvious selectivity and the adsorption capacity retention rate of CP was still 71.32% after four adsorption cycles. This work proposed an easily prepared and biomass-based microspheres for the effective removal of Cr(VI) in printing and dyeing wastewater pollution through adsorption.

Functionalized cotton charcoal/chitosan biomass-based hydrogel for capturing Pb2+, Cu2+ and MB.

In this work, a porous multi-functional biomass carbon was prepared by acid-base modification method, which realized the reuse of waste cotton material. Then, the modified biochar was combined with the acrylic-based hydrogel by radical polymerization, and the biochar acrylic-based hydrogel (CS/EDTA/CBC) composite with chitosan and ethylenediamine tetraacetic acid was successfully prepared. This not only increases the adsorption performance of the adsorbent but also improves the stability of hydrogel. These characteristics provide high-efficiency adsorption capacity for pollutants (1105.78 mg g-1 for Pb2+, 678.04 mg g-1 for Cu2+, and 590.72 mg g-1 for methylene blue (MB)), which is far superior to most reported adsorbents. Meanwhile, the adsorbent would have a strong chemical interaction with Pb2+ and Cu2+, can form a stable chelating structure, and showed stronger selective adsorption. The adsorption process is more suitable for the Langmuir isotherm and follows a pseudo-second-order kinetic model, which indicates that the adsorption is a single-layer adsorption, and the rate-limiting step is a chemical chelation reaction. XPS results confirmed that surface complexation and electrostatic attraction are the main mechanisms of the adsorption reaction. After five cycles, the adsorption capacity of the adsorbent and the recovery of heavy metal ions remained at a high level.