Size,composition,and mixing state of individual aerosol particles in a South China coastal city

Aerosol samples were collected in summer in Macao, a coastal city of the Pearl River Delta Region in China. Morphology, size, elemental composition, and mixing state of individual aerosol particles were determined by scanning electron microscopy coupled energy dispersive X-ray （SEM/EDX） and transmission electron microscopy （TEM）. Based on the morphologies of 5711 aerosol particles, they consist of soot （32%）, mineral （17%）, secondary-（22%）, and unknown fine particles （29%）. The sizes of these particles were mostly distributed between 0.1 and 0.4 μm. Compositions of 202 mineral particles were obtained by SEM/EDX. Mineral particles were mainly classified into three types： Si-rich, Ca-rich, and Na-rich. The compositions of typical mineral particles can indicate their sources in sampling location. For example, mineral particles, collected along the main street, were associated with trace amounts of heavy metals, such as Zn, Ti, Mn, Ba, Pb, and As. TEM observations indicate that most Na-rich particles were aged sea salt particles （e.g., Na2SO4 and NaNO3） which formed through heterogeneous chemical reactions between sea salt and acidic gases. Additionally, aging time of soot was short in Macao due to high humidity, high temperature, and high levels of sunlight in Macao. Most of soot and fine mineral dust particles were internally mixed with secondary particles.

Mg(NO_(3))_(2)·6H_(2O)-Assisted insitu-Fabrication of Tea Residual Biochar for Ultra-Fast and High Adsorption of Rhodamine B

In this work,porous biochar(MN-TRB_(750))was fabricated via direct pyrolysis of tea residue(TR)and Mg(NO_(3))_(2)·6H_(2)O(MN).The as-synthesized MN-TRB_(750) reached a specific surface area of 839.54 m^(2)·g^(-1)and an average pore size of 3.75 nm with multi-level pore architecture.MN decreased TR's carbonization temperature and promoted the aromatics extent,pore structure for the frizzly flake-like biochar.Rhodamine B(RhB)was chosen as the adsorbate to explore the removal performance of organic dyes in this study.The results indicated that the maximum adsorption capacity of RhB on MN-TRB_(750) at 20℃ is up to 809.0 mg·g^(-1)with isotherms fitted well to Freundlich and Dubinin-Radushkevic models.The adsorption kinetics followed pseudo-second-order and Elovich models with an equilibrium adsorption capacity of 757.6 mg·g^(-1)as the initial concentration of RhB is 260 mg·L^(-1).High pore filling,hydrogen bond,π-πinteraction determined the adsorption of RhB onto MN-TRB850 through a multi-active center and exothermic chemical sorption process.

Calcinated Activated Carbon/MgFe-Layered Double Hydroxides for Enhanced Adsorption of Methyl Orange

Series of activated carbon(AC)modified MgFe-layered double hydroxides(LDH/ACs)were synthesized using ultrasonic-assisted co-precipitation method.Herein the mass ratio of Mg/Fe-LDH and AC was varied at 1.55,2.34,and 2.86,respectively.The calcinations of corresponding LDH/ACs were obtained at 723 K for 5 h and named as LDO-AC-1.55,LDO-AC-2.34 and LDO-AC-2.86,respectively.These products were characterized by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),Brunauer-Emmett-Teller(BET)measurements and scanning electron microscopy(SEM).LDO-ACs were applied for the removal of methyl orange(MO).The result showed that aggregation degree of MgFe-LDH decreased in the existence of AC.The pore sizes of LDO-AC-1.55,LDO-AC-2.34 and LDO-AC-2.86 markedly increased with the sharp decreasing of surface area.The values of the statured adsorption capacity of LDO-AC-1.55,LDO-AC-2.34 and LDO-AC-2.86 were obviously higher than those of MgFe-layered double hydroxides fabricated by traditional method(LDO0).The mechanism for the enhanced adsorption may be that the loose macrospore structure of LDO-AC-1.55,LDO-AC-2.34 and LDO-AC-2.86 abbreviates the diffusion resistance and bore repulsive force of MO molecular coupled with its space confinement effect in contrast with LDO0,which is favor for the free self-assembly of MO to form intercalation compound.MO-loaded LDO-AC-2.34 was regenerated by calcination and reused several times,still retaining its original adsorption capacity.