Using FTIR-photoacoustic spectroscopy for phosphorus speciation analysis of biochars

Highly effective removal of malachite green from aqueous solution by hydrochar derived from phycocyanin-extracted algal bloom residues through hydrothermal carbonization

“…The intensities of peaks around 2924 and 2853 cm À1 are increased in the hydrochars. Previous study has shown that these peaks are clearly visible in biomass as well as in the biochars produced at low temperature, but gradually diminished and indiscernible when HTC temperature is above 450 C. 31 In the present study, the temperature of HTC was 200 C, so the C-H stretching vibrations were still present in the samples before and aer HTC treatment. There are no obvious shis of these two peaks with adsorption of MG onto the both hydrochars.…”

“…These peaks are also visible in the spectra of biochars produced by pyrolysis. 31 Obvious shis to 1454 and 1453 cm À1 are also present in the hydrochars with the adsorption of MG, conrming the interaction between the aromatic C-H groups and MG. A broad peak at about 1080 cm À1 corresponding to C-O stretching are separated into two peaks at about 1081 and 1030 cm À1 aer the HTC treatment. The peak at 1030 cm À1 is assigned to Si-O stretching, 32 so it indicates that SiO 2 is formed in the HTC treatment.…”

Characterization and ammonia adsorption of biochar prepared from distillers' grains anaerobic digestion residue with different pyrolysis temperatures

“…The indicator of residual lignin (aromatic C=C stretching) at 1516 cm −1 gradually decreased with increasing temperature. The peak corresponding to symmetric C-H bending (1384 cm −1 ) was already removed at 400 ∘ C, which was higher than the results of Bekiaris et al 38 of 300 ∘ C. The band intensities at 1100 cm −1 due to the stretching of silicon-containing groups (Si-O-Si) indicated that the BR had large amounts of silicon. 39 At 300 ∘ C, a broad, weak peak at 800 cm −1 assigned to the C-H out of plane vibration of aromatic compounds 40 appeared and remained visible until 600 ∘ C.…”

“…8 The intensity of the peak around 1600 cm −1 was only visible as a shoulder at 600 ∘ C, then absent in the spectra at 700 and 800 ∘ C, which may be explained by dilution of the aromatic compounds in the increasing ash content (Table 1). 38 Higher temperature, especially 700 and 800 ∘ C, resulted in more substantial chemical transformations. The indicator of residual lignin (aromatic C=C stretching) at 1516 cm −1 gradually decreased with increasing temperature.…”

Changes in structural and chemical properties of rice husk biochar co-pyrolysed with Eppawala rock phosphate under different temperatures

“…Certain new peaks were formed as a result of the ERP incorporation during pyrolysis which showed by wave numbers 973 cm -1 and 1175 cm -1 . According to Bekiaris et al (2016) weak stretch at 975 cm -1 represented tribasic calcium phosphates and 1160 cm -1 corresponded to amorphous dibasic calcium phosphate. Since the chemical formula of the main constituent of ERP, apatite, is (Ca5(PO4)3.OH,F,Cl), the observed stretches at 973 and 1175 cm -1 could be due to the reactions between ERP and carbon structure of rice husk biochar.…”