Significant concerns have been raised over pollution of antibiotics including tetracyclines in aquatic environments in recent years. Graphene oxide (GO) is a potential effective absorbent for tetracycline antibiotics and can be used to remove them from aqueous solution. Tetracycline strongly deposited on the GO surface via π-π interaction and cation-π bonding. The adsorption isotherm fits Langmuir and Temkin models well, and the theoretical maximum of adsorption capacity calculated by Langmuir model is 313 mg g(-1), which is approximately in a close agreement with the measured data. The kinetics of adsorption fits pseudo-second-order model perfectly, and it has a better rate constant of sorption (k), 0.065 g mg(-1) h(-1), than other adsorbents. The adsorption capacities of tetracycline on GO decreased with the increase in pH or Na(+) concentration. The adsorption isotherms of oxytetracycline and doxycycline on GO were discussed and compared.

Adsorption and removal of tetracycline antibiotics from aqueous solution by graphene oxide

Review of antibiotic resistance in China and its environment

Advanced oxidation process-mediated removal of pharmaceuticals from water: A review.

The very wide use of glyphosate to control weeds in agricultural, silvicultural and urban areas throughout the world requires that special attention be paid to its possible transport from terrestrial to aquatic environments. The aim of this review is to present and discuss the state of knowledge on sorption, degradation and leachability of glyphosate in soils. Difficulties of drawing clear and unambiguous conclusions because of strong soil dependency and limited conclusive investigations are pointed out. Nevertheless, the risk of ground and surface water pollution by glyphosate seems limited because of sorption onto variable-charge soil minerals, e.g. aluminium and iron oxides, and because of microbial degradation. Although sorption and degradation are affected by many factors that might be expected to affect glyphosate mobility in soils, glyphosate leaching seems mainly determined by soil structure and rainfall. Limited leaching has been observed in non-structured sandy soils, while subsurface leaching to drainage systems was observed in a structured soil with preferential flow in macropores, but only when high rainfall followed glyphosate application. Glyphosate in drainage water runs into surface waters but not necessarily to groundwater because it may be sorbed and degraded in deeper soil layers before reaching the groundwater. Although the transport of glyphosate from land to water environments seems very limited, knowledge about subsurface leaching and surface runoff of glyphosate as well as the importance of this transport as related to ground and surface water quality is scarce.

Fate of glyphosate in soil and the possibility of leaching to ground and surface waters: a review.

Carbon quantum dots (CDs) have been frequently used for broadening spectrum light response due to their superior up-conversion photoluminescence (UPPL) property and effective charge separation capacity. In this study, a novel CDs modified Z-scheme photocatalyst (CDs/g-C3N4/MoO3) was successfully constructed. The morphologies, chemical compositions, and optical properties of the prepared catalysts were investigated via a series of characterization techniques. Systematic studies indicated that the CDs/g-C3N4/MoO3 photocatalyst exhibited remarkably enhanced visible-light photocatalytic activity for the degradation of tetracycline (TC) compared to pristine g-C3N4 and MoO3/g-C3N4 composite. Doping 0.5% CDs resulted in the highest TC degradation rate, which was 3.5 and 46.2 times higher than that of MoO3/g-C3N4 and g-C3N4, respectively. The enhanced photocatalytic performance of CDs/g-C3N4/MoO3 can be attributed to the synergistic effects of CD properties (i.e., excellent UPPL activity and high charge separation capacity and the Z-scheme heterojunction structure). Reactive species scavenging experiments revealed that photogenerated holes are the main active species during the photocatalytic process. Possible photocatalytic degradation pathways of TC were proposed through the identification of intermediates using HPLC-MS and the frontier electron density calculation. Experimental results showed that the newly fabricated Z-scheme CDs/g-C3N4/MoO3 is a promising photocatalyst for the removal of TC from the environment.

Construction of carbon dots modified MoO3/g-C3N4 Z-scheme photocatalyst with enhanced visible-light photocatalytic activity for the degradation of tetracycline

http://www.soilrem.ac.cn/files/project/20131031153245355.pdf

Photocatalytic degradation of tetracycline in aqueous solution by nanosized TiO2.

Land application of wastes generated from concentrated animal feeding operations may result in accumulation of tetracyclines (TCs) and metals in agricultural soils. Adsorption of TCs and metals on soil minerals strongly affects their mobility. This study was conducted to evaluate the interaction between tetracycline (TC) and Cu(ll) with regard to their adsorption and cosorption on montmorillonite as affected by solution pH. When solution pH was below 6.5, the presence of TC increased Cu(ll) adsorption on montmorillonite, which could be due to increasing Cu(II) adsorption via the TC bridge, or due to the stronger affinity of TC-Cu(II) complex to the mineral than Cu2+ ion itself. Zeta potential of the montmorillonite significantly decreased after the adsorption of TC, suggesting a strong interaction between TC and montmorillonite. Addition of Cu(ll) ions increased TC adsorption on the mineral in a wide range of pH. The experimental data were well fit with the weighted sum model. The complexes of TC and Cu(II) (CuH2L(2+), CuHL+, and CuL) had higher sorption coefficients (K(d)) than that of the corresponding TC species (H3L+, H2L, and HL-). Increasing adsorption of TC and Cu(II) on montmorillonite as they coexist in the normal pH environment may thus reduce their mobility.

Adsorption and cosorption of tetracycline and copper(II) on montmorillonite as affected by solution pH.

http://www.soilrem.ac.cn/files/project/20131031161556194.pdf

Subacute toxicity of copper and glyphosate and their interaction to earthworm (Eisenia fetida).

Phosphate affects the adsorption of tetracycline on two soils with different characteristics

Phosphate compounds and related materials are effective amendments for immobilization of heavy metals in contaminated soils. A greenhouse pot experiment with ryegrass (Lolium perenne) as the test plant was conducted to explore the impact of nanoparticle hydroxyapatite (HAP) on the immobilization and bioavailability of Cu and Zn in a heavy metal-polluted soil. The addition of nanoparticle HAP significantly decreased the uptake of Cu and Zn by ryegrass. As a result, the biomass of ryegrass increased as the rate of nanoparticle HAP increased. The toxicity characteristic leaching procedure (TCLP) and physiologically based extraction test (PBET) results of the treatments showed that the leachable and bioaccessible concentrations of Cu and Zn were significantly reduced after the soil stabilized with nanoparticle HAP. The XRD pattern of nanoparticle HAP was not changed by the presence of Cu and Zn, which suggests that Cu and Zn were immobilized by the formation of solid amorphous phosphate. Nanoparticle HAP was an effective material to immobilize heavy metals in contaminated soils.

Rui-Juan Sun

Papers

Photocatalytic degradation of tetracycline in aqueous solution by nanosized TiO2.

Adsorption and cosorption of tetracycline and copper(II) on montmorillonite as affected by solution pH.

Subacute toxicity of copper and glyphosate and their interaction to earthworm (Eisenia fetida).

Phosphate affects the adsorption of tetracycline on two soils with different characteristics

Effect of nanoparticle hydroxyapatite on the immobilization of Cu and Zn in polluted soil.