Efficient removal of Cd (II) from aqueous solution by chitosan modified kiwi branch biochar.

Production of cost-efficient composite materials from low-cost modified biochar for the removal of Cd (II) from wastewater is much needed to meet the growing needs of industrial wastewater treatments. A novel chitosan-modified kiwi branch biochar (CHKB) was fabricated as low-cost modified biochar for the removal of Cd (II) from aqueous solution. Batch adsorption and characterization experiments indicated that the modification of kiwi biochar (KB) by chitosan remarkably improved its adsorption performance. The results revealed that the adsorption isotherms can be best described by a Langmuir model and that a pseudo-second-order model fits the Cd (II) adsorption kinetics well, which indicates that it is a monolayer process controlled by chemisorption. CHKB exhibited a Langmuir maximum adsorption capacity of Cd (II) (126.58 mg g-1), whereas that of KB was only 4.26 mg g-1. The adsorption ability of CHKB was improved by increasing the surface area and an abundance of surface functional groups (-OH, -NH, CO, etc.). The cation exchange, electrostatic interaction, surface complexation, and precipitation were the main mechanisms in the sorption of Cd (II) on CHKB. Excellent adsorption performance, low cost, and environmental-friendliness made CHKB a fantastic adsorbent for the removal of Cd (II) in wastewater.

Novel Zn-Fe engineered kiwi branch biochar for the removal of Pb(II) from aqueous solution.

In this study, a novel adsorbent made from kiwi branch biochar modified with Zn-Fe (KB/Zn-Fe) was compared with original biochar to the Pb(II)'s adsorptivity from waste water. The adsorbent was synthetized by liquid-phase deposition. Batches of sorption tests were performed, and the biochars' representative properties were tested. Characterizations revealed the physicochemical properties of biochars and showed that the KB/Zn-Fe composites were successfully synthesized. The Langmuir model and pseudo-second-order kinetic model were proven to satisfactorily fit the original biochar and KB/Zn-Fe. The KB/Zn-Fe showed Langmuir maximum adsorption ability to Pb (II) in aqueous solution of 161.29 mg g-1, compared with 36.76 mg g-1 for original biochar. The adsorption ability of Pb(II) decreased and the Pb(II) removal efficiency increased with increasing biochar dose. The effect of co-existence of NO3- to the absorptive capacity of KB/Zn-Fe on Pb(II) was unremarkable, but Cl- could increase the absorptive capacity. Multiple Pb(II) adsorption mechanisms by KB/Zn-Fe include surface precipitation of metal hydroxides, complexation with active functional groups and ion-exchange. This work provides guidance for future production of biochar with efficient adsorption ability, which could be used to remove Pb(II) ions from wastewater.

Co-transport of graphene oxide and heavy metal ions in surface-modified porous media.

The ability to predict the transport of heavy metal ions in porous media with different surface characteristics is crucial to protect groundwater quality and public health. In this study, the effects of graphene oxide (GO) on co-transport and remobilization of Pb2+ and Cd2+ in humic acid (HA), smectite, kaolinite, and ferrihydrite-coated sand media were evaluated via laboratory packed-column experiments. Scanning electron microscope and energy dispersive X-ray analysis showed that the surface morphology of the coated sands was quite different and that ∼56.7-89.9% of the surface was covered by the coating and the major elemental components were C, O, Si, Al, and Fe. GO exhibited high mobility in HA, kaolinite, and smectite-coated sand, but showed high retention in ferrihydrite-coated sand. While GO reduced the transport of Pb2+ and Cd2+, both metal ions also reduced the mobility of GO in coated-sand columns. Elution experiments revealed that GO led to the remobilization and release of the previously sorbed Pb2+ and Cd2+ from the coated sand. However, GO could not release Pb2+ and Cd2+ from smectite-coated sand columns, probably because smectite has stronger adsorption affinity to the heavy metals than GO. Derjaguin-Landau-Verwey-Overbeek calculations were employed and explained the GO transport behavior in the columns well. Furthermore, the advection-dispersion-reaction equation simulated the cotransport of Pb2+ and Cd2+ with GO in the coated sand well. These results are expected to provide insight into the potential impact of coexisting nanomaterials with contaminants in vulnerable soil and groundwater systems.

[Effect of Long-term Organic Amendments on Nitric Oxide Emissions from the Summer Maize-Winter Wheat Cropping System in Guanzhong Plain].

Agricultural soil is a significant source of nitric oxide (NO). The primary aim of this study was to quantify the effect of long-term organic amendments on NO emissions from the summer maize-winter wheat cropping system in Guanzhong Plain. NO fluxes were regularly measured by the static chamber method for one year (June 2016 to June 2017). Field experiments included four fertilizer treatments that commenced in 1990. The control (CK, 0 kg·hm-2) treatment was unfertilized throughout the years. The fertilized treatments were synthetic fertilizer (NPK, 165 kg·hm-2), synthetic fertilizer plus maize stalk (NPKS, (165+40) kg·hm-2), and synthetic fertilizer plus dairy manure (NPKM, (50+115) kg·hm-2) during the winter wheat season. They were fertilized with synthetic fertilizer (188 kg·hm-2) during the summer maize season. The results showed small NO emission [<12.2 g·(hm2·d)-1] from the CK treatment within the experimental period. Large NO fluxes [up to 112.0 g·(hm2·d)-1 in NPK treatment] were captured following sowing and fertilization during the summer maize season and following fertilization during the winter wheat season for all fertilized treatments. Annual NO emissions and direct emission factors ranged from 0.13 to 0.57 kg·hm-2 and from 0.04% to 0.12%, respectively. Annual NO emissions from the NPKS and NPKM treatments were 17.6% lower and 68.0% (P<0.05) larger than those from the NPK treatment, respectively. Seasonal NO emissions from the NPKS and NPKM treatments were 41.1%-60.0% (P<0.05) lower than those from the NPK treatment during the winter wheat season, indicating that organic amendments reduced NO emissions. Seasonal NO emissions from the NPKS and NPKM treatments were 25.2%-292.1% (P<0.05) larger than that from the NPK treatment during the summer maize season, mostly due to the positive effect of soil organic matter content on NO emissions.

Preparation and physical properties of a novel biocompatible porcine corneal acellularized matrix.

This study was to investigate the stability, physico-mechanical property and biocompatibility of porcine corneal acellularized matrix (PCAM) that was prepared using human sera treatment to decellularize corneas. The stability (the rate of biodegradation) and physico-mechanical property (water uptake, density, and porosity) of PCAM were not compromised, compared with porcine fresh cornea matrix (PFCM, p > 0.05). The contact and extract cytotoxicity tests with human corneal epithelial cells and human keratocytes showed that PCAM has a good biocompatibility ex vivo and no cytotoxic effect. These results present the ability to create safety scaffolds that function as cornea grafts and provide a novel experimental approach for the study of cornea tissue engineering using acellular porcine cornea.