Impacts and Mechanisms of Natural Organic Matter and pH on the Transport of Nanobiochar

doi:10.19657/j.geoscience.1000-8527.2018.01.11

Abstract

Abstract:

Biochar, a kind of typical black carbon, has attracted attention for its application development in recent years. Since biochar is applied into the soils, some would gradually become fragmented into micro or nano sized biochar particles under the long term supergene geochemical process. It is very important to investigate the transport of biochar, specially, more reactive nanobiochar. Whereas, such research is few up to now. Hence, the column experiments were conducted on the transport of nanobiochar in quartz sand column to explore the breakthrough curve and retention curve. The aim of the present study is to elucidate the mechanism of the effects of natural organic matter (NOM) and different pH values (pH=4,7,10) on nanobiochar transport behavior. The results showed that humic acid (HA, a model NOM) enhanced the mobility of nanobiochar, and neutral or alkaline aqueous medium favored nanobiochar transport. One reason is that the dispersibility of nanobiochar was improved. The other is due to net negative charge of biochar and quartz particles increased in the presence of HA and alkaline environment. So, the Zeta potential of particles increased and electrostatic repulsion force strengthened, which was beneficial to the transport of nanobiochar. This work is of importance to understand the geochemical transport behavior of nanobiochar and the potential risk of contaminant adsorption onto nanobiochar transported in the environment.

Key words: nanobiochar, transport, column experiment, humic acid, pH value in the environment

CLC Number:

X142

YANG Meihong, LI Zhixiong, LIU Yuyan, MA Shaoqiang, CHEN Jiawei. Impacts and Mechanisms of Natural Organic Matter and pH on the Transport of Nanobiochar[J]. Geoscience, 2018, 32(01): 113-120.

Figures/Tables 9

Fig.1 Sketch of column experiment

Fig.2 The absorbance curve of nanobiochar suspension (A) UV-Vis scanning spectra;(B) Standard curve

Fig.3 TEM image of biochars (A) Biochar micro-particle;(B) Boichar nanoparticle

Fig.4 Aggregation size distribution of biochar nanoparticles under the effect of HA

Fig.5 Transport of nanobiochar under the effect of HA (A) Breakthrough curve;(B) Retention curve

Table 1 Mass balance of total nanobiochar (Mtot) from effluent (Meff) and retention (Mret)

柱实验编号	HA/ (mg/L)	pH	M_eff/%	M_ret/%	M_tot/%
1	0	7	80.9	18.6	99.5
2	15	4	86.7	18.8	105.5
3	15	4	86.7	16.5	103.2
4	15	7	94.0	12.1	106.1
5	15	7	94.1	12.1	106.2
6	15	10	98.1	12.4	110.5
7	15	10	98.1	13.4	111.5

Fig.6 Effect of pH on the transport of nanobiochar (A) Breakthrough curve;(B) Retention curve

Fig.7 Zeta potential of quartz sand and nanobiochar (A) The presence or absence of HA;(B) Different pH condition

Fig.8 Mechanism of transport of nanobiochar under the effect of pH and humic acid

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