In situ nano-silicate functionalized magnetic composites by (poly)dopamine to improve MB removal

Starch-Based Polymer Materials as Advanced Adsorbents for Sustainable Water Treatment: Current Status, Challenges, and Future Perspectives

Over the past three decades, chemical and biological water contamination has become a major concern, particularly in the industrialized world. Heavy metals, aromatic compounds, and dyes are among the harmful substances that contribute to water pollution, which jeopardies the human health. For this reason, it is of the utmost importance to locate methods for the cleanup of wastewater that are not genuinely effective. Owing to its non-toxicity, biodegradability, and biocompatibility, starch is a naturally occurring polysaccharide that scientists are looking into as a possible environmentally friendly material for sustainable water remediation. Starch could exhibit significant adsorption capabilities towards pollutants with the substitution of amide, amino, carboxyl, and other functional groups for hydroxyl groups. Starch derivatives may effectively remove contaminants such as oil, organic solvents, pesticides, heavy metals, dyes, and pharmaceutical pollutants by employing adsorption techniques at a rate greater than 90%. The maximal adsorption capacities of starch-based adsorbents for oil and organic solvents, pesticides, heavy metal ions, dyes, and pharmaceuticals are 13,000, 66, 2000, 25,000, and 782 mg/g, respectively. Although starch-based adsorbents have demonstrated a promising future for environmental wastewater treatment, additional research is required to optimize the technique before the starch-based adsorbent can be used in large-scale in situ wastewater treatment.

Immobilization of psychrophile Psychrobacter sp. ANT206 onto novel reusable magnetic nanoparticles and its application for nitro-aromatic compounds biodegradation under low temperature

Efficient biodegradation may offer a solution for the treatment of nitro-aromatic compounds (NACs) with toxicity, mutagenicity and persistence in the environment. In this study, dopamine (DA) functionalized magnetic nanoparticles with biocompatibility and hydrophilicity were synthesized and utilized for the immobilization of nitro-aromatic compounds degrading psychrophile Psychrobacter sp. ANT206 harboring the cold-adapted nitroreductase. The prepared nanocarriers were characterized using multiple methods. The highest immobilization yield of cells immobilized by Fe3O4@SiO2@DA was 90.67% under the optimized conditions of 10 °C, pH 7.5, 2 h and cell/support 1.2 mg/mg, and the activity recovery was 89.41%. In addition, the obtained immobilized cells displayed excellent salinity stability and reusability. Moreover, immobilized P. sp. ANT206 strains showed remarkable biodegradation capability on nitrobenzene and p-nitrophenol. This study introduced those novel Fe3O4@SiO2@DA nanoparticles could be applied as ideal and low-cost nanocarriers for the immobilization of cells and large-scale bioremediation of hazardous NACs with perspective applications under low temperature.

Eco-Friendly NiO/Polydopamine Nanocomposite for Efficient Removal of Dyes from Wastewater

The rapid development of industries discharges huge amounts of wastewater that contain surface water. For this reason, we used NiO/polydopamine (NiO/PDA) nanocomposite as an efficient material for the removal of Methyl violet 2B from water. It was synthesized and then characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), and Brunauer–Emmett–Teller (BET). The EDX analysis confirmed the presence of O, Ni, N, and C. The composite has an average particle size of 18 nm. Its surface area is 110.591 m2/g. It was found that the efficiency of dye removal by adsorption on NiO/PDA exceeded that of bare NiO. The adsorption capacity of NiO and NiO/PDA are 126 and 284 mg/g, respectively. The effects of adsorbent dose, dye concentration, and pH on the removal efficiency were examined. The efficiency increased with increasing the adsorbent dose and pH, but dropped from 85 to 73% within 30 min as the initial dye concentration was increased from 0.984 to 4.92 mg/L. Such a drop in the removal efficiency is due to the blocking of the surface-active sites of NiO/PDA, with the high population of dye molecules derived from the continuous increase in dye concentration. The adsorption results of the dye fitted well with the pseudo-second-order kinetics and Langmuir isotherm. The reusability data showed that NiO/PDA was stable across three adsorption–regeneration cycles, thus it can be considered a good recyclable and efficient adsorbent. Because of these results, it can be considered that this method can be applied for the treatment of wastewater.

A novel Fe3+-stabilized magnetic polydopamine composite for enhanced selective adsorption and separation of Methylene blue from complex wastewater

Herein, a novel Fe³⁺-stabilized magnetic polydopamine composite (Fe₃O₄/PDA-Fe³⁺) was facilely constructed, systematically characterized, and subsequently applied for the first time as a versatile adsorbent for treatment of Methylene blue (MB) in complex wastewater. Results showed that as-prepared material had prominent adsorption ability toward MB in its single dye solution over a wide pH range (3-10) with q_max value of 608.8 mg/g at 318 K. More interestingly, MB could be selectively captured by resulting adsorbent from mixed dye solutions (MB-cationic dye and MB-anionic dye) and complex aqueous solution with high ionic strength up to 0.5 mol/L NaCl. It was eventually revealed that the enhanced and selective adsorption of MB by as-resultant adsorbent was due to the synergistic effects between multiple uptake mechanisms. What's more, its adsorption efficiency toward MB in simulated wastewater still maintained higher than 80 % of its original uptake performance after several runs of adsorption-desorption. Additionally, it exhibited more superior uptake performance toward MB than commercial powder activated carbon (PAC) in column adsorption system. Thus, the outstanding sorption ability, unique capture selectivity, as well as excellent stability and recyclability for model wastewater endow it a promising candidate adsorbent for selective adsorption and separation of MB from complex wastewater.

Polydopamine modified cyclodextrin polymer as efficient adsorbent for removing cationic dyes and Cu2

An eco-friendly polydopamine composite adsorbent (CD-CA/PDA) based on cyclodextrin polymer was prepared for cationic dyes and metals removing. CD-CA/PDA, combining the advantages of cyclodextrin and polydopamine, which has quite abundant carboxyl and catechol groups, so methylene blue (MB), malachite green (MG), crystal violet (CV) and copper ion (Cu²⁺) can be easily removed by electrostatic force. Adsorption kinetic results showed all adsorption process fitted well with pseudo-second-order model. In addition, the isotherm fitted results showed that the adsorption processes of CD-CA/PDA on MG and Cu²⁺ were consistent with sips model, while the adsorption processes of MB and CV agreed well with Freundlich and Langmuir model, respectively. The fitted adsorption capacities of CD-CA/PDA for MB, MG, CV and Cu²⁺ were 582.95 mg/g (1.82 mmol/g), 1174.67 mg/g (3.22 mmol/g), 473.01 mg/g (1.16 mmol/g) and 73.64 mg/g (1.16 mmol/g), respectively. Moreover, it is worth noting that cationic dyes have no competitive adsorption in series. CD-CA/PDA is of great recyclability, and can be reused by at least 5 times. Due to the facile and eco-friendly preparation process and excellent adsorption performance, CD-CA/PDA has a great potential in the field of wastewater treatment.

The polyaminocarboxylated modified hydrochar for efficient capturing methylene blue and Cu(II) from water

The polyaminocarboxylated modified hydrochar (ACHC) was synthesized to introduce abundant amino, hydroxyl and carboxylate multifunctional groups onto the surface of hydrochar by etherification, amination and carboxylated reaction. The ACHC was systematically characterized and used to evaluate adsorption properties of Cu(II) and methylene blue (MB) by batch sorption tests. The adsorption process toward Cu(II) and MB by ACHC obeyed the pseudo-second-order kinetic model and Langmuir model. Characteristic analysis indicated the surface chelation was mainly contribute to Cu(II) adsorption by large amounts of amino and carboxylate groups while π-π interaction, hydrogen bonding and electrostatic attraction dominated MB adsorption. The maximum adsorption capacities of ACHC were 140.65 and 1238.66 mg·g^-1 for Cu(II) and MB at 303 K, respectively. Approximately 97% of the adsorptive uptakes for two pollutants were removed within merely 5 min for kinetic experiment. Competitive adsorption of Cu(II) and MB, and treatment of electroplating wastewater by ACHC were also investigated.