Linglin Zhou

Synthesis of a Multifunctional Graphene Oxide-Based Magnetic Nanocomposite for Efficient Removal of Cr(VI)

A novel magnetic nanocomposite was synthesized using graphene oxide (GO), polyethylenimine (PEI), and Fe3O4 to removal hexavalent chromium (Cr(VI)) from water and soil. Therein, GO was functionalized with plenty of -NH2 by the modification of PEI through an amidation reaction, and the resulting GO/PEI reacted with FeSO4·7H2O and NaBH4 to obtain RGO/PEI/Fe3O4 (the optimal one is designated as ORPF) through an oxidation-reduction reaction. ORPF could effectively adsorb Cr(VI) through electrostatic attraction, and the adsorbed Cr(VI) ions were partially reduced to trivalent chromium (Cr(III)) with low toxicity by RGO (π electron). Afterward, the resulting ORPF-Cr could be conveniently removed from water with a magnet, achieving the maximum Cr(VI) removal capacity of 266.6 mg/g. Importantly, ORPF, once carried by sponge particles, could efficiently remove Cr(VI) from soil, and the resulting mixture could be facilely collected with a magnet on a filter net. Besides, the leaching experiment suggested that, when supported by filter paper, ORPF was able to decrease the number of leached Cr(VI) ions and meanwhile reduce them to Cr(III). This work provides a promising approach to remediate Cr(VI)-contaminated water and soil using a nanocomposite, which has a huge number of application prospects.

Immobilizing arsenic and copper ions in manure using a nanocomposite

Livestock manure (Man) commonly contains a certain quantity of heavy metal ions, such as arsenic (As) and copper (Cu) ions, resulting in a high risk on soil contamination. To solve this problem, heavy metal of manure was immobilized into sodium carbonate/biosilica/attapulgite composite (Na2CO3/BioSi/Attp), which was developed using a nanocomposite consisting of anhydrous sodium carbonate (Na2CO3), straw ash-based biochar and biosilica (BioSi), and attapulgite (Attp). When Na2CO3/BioSi/Attp was mixed with Man/AsCu, the obtained nanocomposite (Na2CO3/BioSi/Attp/Man/AsCu) with a porous nano-network structure could effectively control the release of As and Cu ions from manure through adsorption and chemical reaction. Meanwhile, a pot experiment indicated that Na2CO3/BioSi/Attp/Man/AsCu could increase the pH value of acid soil, promote the growth of rice, and significantly decrease the uptake of As and Cu ions by rice. Therefore, this work provides a promising approach to immobilize heavy metal ions in manure and, thus, lower the contamination risk to the environment. Na2CO3, BioSi, and Attp powders were mixed evenly with a weight ratio of WNa2CO3/WBioSi/WAttp = 3:1:2.

Sandwich-like Nanosystem for Simultaneous Removal of Cr(VI) and Cd(II) from Water and Soil

In this work, a novel nanosystem with a sandwich-like structure was synthesized via face-to-face combination of two pieces of waste cotton fabrics (CFs) carrying ferrous sulfide (FeS) and carboxyl-functionalized ferroferric oxide microsphere (CFFM), respectively, and the obtained nanosystem was named as FeS/CFFM/CF. Therein, FeS has high reduction and adsorption capabilities for hexavalent chromium (Cr(VI)), CFFM possesses a high adsorption ability on cadmium ion (Cd(II)) through electrostatic attraction and chelation, and CF displays high immobilization ability for FeS and CFFM and adsorption performance on Cd(II). FeS/CFFM/CF could simultaneously remove Cr(VI) and Cd(II) from water and inhibit the uptake of Cr and Cd by fish and water spinach, ensuring the food safety. Besides, this technology could efficiently control the migration of Cr(VI) and Cd(II) in the sand-soil mixture, which was favorable to prevent their wide diffusion. Importantly, FeS/CFFM/CF possessed a high flexibility and could be conveniently produced with needed scale and shape and easily separated from water and soil, displaying a promising approach to remediate Cr(VI)-/Cd(II)-contaminated water and soil and a huge application potential.

Controlling the Hydrolysis and Loss of Nitrogen Fertilizer (Urea) by using a Nanocomposite Favors Plant Growth

Urea tends to be hydrolyzed by urease and then migrate into the environment, which results in a low utilization efficiency and severe environmental contamination. To solve this problem, a network-structured nanocomposite (sodium humate-attapulgite-polyacrylamide) was fabricated and used as an excellent fertilizer synergist (FS) that could effectively inhibit the hydrolysis, reduce the loss, and enhance the utilization efficiency of nitrogen. Additionally, the FS exerted significant positive effects on the expression of several nitrogen-uptake-related genes, ion flux in maize roots, the growth of crops, and the organic matter in soil. The FS could modify the microbial community in the soil and increase the number of bacteria involved in nitrogen metabolism, organic matter degradation, the iron cycle, and photosynthesis. Importantly, this technology displayed a high biosafety and has a great potential to reduce nonpoint agricultural pollution. Therefore, this work provides a promising approach to manage nitrogen and to promote the sustainable development of agriculture and the environment.

Waste Carton-Derived Nanocomposites for Efficient Removal of Hexavalent Chromium

A new nanocomposite (SCZ), microspherical carbon (SC) loaded with nanoscale zerovalent iron (ZVI), was fabricated to efficiently remove hexavalent chromium (Cr(VI)) in water. Therein, SC was derived from waste carton through hydrothermal treatment after pretreatment of removing hemicellulose and lignin, and the optimal hydrothermal conditions (200 °C, hydrothermal time of 12 h) for the preparation of SC were obtained. Subsequently, SC could effectively load ZVI nanoparticles which displayed high dispersion on the surface of SC and in the pores among SC particles owing to steric hindrance effect. The obtained SCZ displayed a high removal efficiency of 100% within 5 h on Cr(VI) (20 mg/L), and the resultant SCZ-Cr could be conveniently separated from water because of its magnetism. Importantly, SCZ could be loaded in cardboard, and the obtained system could serve as a stable filter for removal of Cr(VI) in water. This work provides a cheap and effective method for Cr(VI) removal, which also greatly facilitates the recycling of waste carton.