9.24.3
Ca bonized Apples and Quinces
S illage o Elec omagne ic
Shielding
Mila Milenko ic, Wa da Saeed, Muhammad Yasi , Dusan Mili oje ic, Ali Azmy, Kamal E. S. Nassa ,
Zois Sy giannis, Ioannis Spanopoulos, Danica Bajuk-Bogdano ic, Snežana Male ić e al.
A icle
h ps://doi.o g/10.3390/nano14231882
Ci a ion: Milenko ic, M.; Saeed, W.;
Yasi , M.; Mili oje ic, D.; Azmy, A.;
Nassa , K.E.S.; Sy giannis, Z.;
Spanopoulos, I.; Bajuk-Bogdano ic,
D.; Male i´c, S.; e al. Ca bonized
Apples and Quinces S illage o
Elec omagne ic Shielding.
Nanoma e ials 2024,14, 1882. h ps://
doi.o g/10.3390/nano14231882
Academic Edi o : Jose L. A ias
Recei ed: 3 Oc obe 2024
Re ised: 29 Oc obe 2024
Accep ed: 22 No embe 2024
Published: 23 No embe 2024
Copy igh : © 2024 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
A icle
Ca bonized Apples and Quinces S illage o Elec omagne ic
Shielding
Mila Milenko ic 1, Wa da Saeed 2, Muhammad Yasi 2,* , Dusan Mili oje ic 1, Ali Azmy 3,
Kamal E. S. Nassa 3, Zois Sy giannis 3, Ioannis Spanopoulos 3, Danica Bajuk-Bogdano ic 4,
Snežana Male i´c 5, Dju dja Ke kez 5, Tanja Ba udžija 1and S e lana Jo ano i´c 1,*
1Vinˇca Ins i u e o Nuclea Sciences—Na ional Ins i u e o he Republic o Se bia, Uni e si y o Belg ade,
P.O. Box 522, 11000 Belg ade, Se bia; [email p o ec ed] (M.M.)
2Depa men o Compu ing Science, Mic o obo ics and Con ol Enginee ing, Ca l on Ossie zky Uni e si ä
Oldenbu g, 26129 Oldenbu g, Ge many; [email p o ec ed]
3Depa men o Chemis y, Uni e si y o Sou h Flo ida, Tampa, FL 33620, USA; [email p o ec ed] (I.S.)
4Facul y o Physical Chemis y, Uni e si y o Belg ade, S uden ski T g 12–16, 11158 Belg ade, Se bia
5
Depa men o Chemis y, Biochemis y and En i onmen al P o ec ion, Facul y o Science, Uni e si y o No i
Sad, T g Dosi eja Ob ado i´ca 3, 21000 No i Sad, Se bia
*Co espondence: [email p o ec ed] (M.Y.); [email p o ec ed] (S.J.)
Abs ac : Elec omagne ic wa es (EMWs) ha e become an in eg al pa o ou daily li es, bu hey
a e causing a new o m o en i onmen al pollu ion, mani es ing as elec omagne ic in e e ence (EMI)
and adio equency signal leakage. As a esul , he demand o inno a i e, eco- iendly ma e ials
capable o blocking EMWs has escala ed in he pas decade, unde sco ing he signi icance o ou
esea ch. In he ealm o mode n science, he c ea ion o new ma e ials mus conside he s a ing
ma e ials, p oduc ion cos s, ene gy usage, and he po en ial o ai , wa e , and soil pollu ion. He ein,
we u ilized biowas e ma e ials gene a ed du ing he dis illa ion o ui schnapps. The biowas e
om apple and quince schnapps dis illa ion was used as s a ing ma e ial, mixed wi h KOH, and
ca bonized a 850
◦
C, in a ni ogen a mosphe e. The s uc u e o samples was in es iga ed using
a ious echniques (in a ed, Raman, ene gy-dispe si e X- ay, X- ay pho oelec on spec oscopies,
he mog a ime ic analysis, BET su ace a ea analyze ). Encou agingly, hese ma e ials demons a ed
he abili y o block EMWs wi hin a equency ange o 8 o 12 GHz. Shielding e iciency was measu ed
using wa eguide adap e s connec ed o po s (1 and 2) o he ec o ne wo k analyze using adio-
equency coaxial cables. A a equency o 10 GHz, ca bonized biowas e blocks 78.5% o he inciden
elec omagne ic wa e.
Keywo ds: g aphene; g aphene oxide; biowas e; ca boniza ion; elec omagne ic in e e ence shielding
1. In oduc ion
Aside om he adi ional o ms o pollu ion caused by chemicals in gaseous, liquid,
o solid s a es, such as mic o- and nano-plas ics, mode n socie y is now g appling wi h a
new ype o pollu ion, i.e., elec omagne ic wa es (EWs). The p oli e a ion o de ices in ou
daily li es, he expansion o elecommunica ion in as uc u e, and he e olu ion o wi eless
echnologies has unde sco ed he c i ical need o inno a i e ma e ials capable o blocking
he p opaga ion o EWs. Elec omagne ic in e e ence (EMI) is pa icula ly de imen al
in he case o sensi i e measu emen de ices, po en ially leading o a educ ion in he
ins umen ’s li espan, unwan ed in e e ence signals, and p olonged measu ing imes.
Thus, new ma e ials, in he o m o powde , oil, and ab ic, which can e icien ly block
elec omagne ic wa e p opaga ion, ha e become mo e c i ical in ecen yea s [
1
–
3
]. S udies
ha e sugges ed ha me als, me al composi es, and conduc i e polyme s ha e excellen
EMI shielding p ope ies [
4
–
6
]. New nanoma e ials, such as silk- lowe -like NiO wi h
a hie a chical s uc u e, showed a e lec ion loss (R
L
) o –65.1 dB a 13.9 GHz due o i s
Nanoma e ials 2024,14, 1882. h ps://doi.o g/10.3390/nano14231882 h ps://www.mdpi.com/jou nal/nanoma e ials
Nanoma e ials 2024,14, 1882 2 o 16
hie a chical and po ous s uc u es, mul iple sca e ing e ec s om nanoshee s, olds and
oids, di e en impedance ma ching cha ac e is ics, and clus e ed de ec s, whe e oxygen
acancies could dis up he cha ge dis ibu ion balance and induce dipole pola iza ion
and ela ed elaxa ions [
7
]. A lexible, semiconduc i e de ice was ab ica ed using ca bon
nano ubes wi h a unable elec omagne ic wa e abso p ion equency [
8
]. Howe e , hese
ma e ials a e o en sensi i e o en i onmen al condi ions, such as humidi y [
9
], o ha e
limi ed p ocessabili y, e.g., conduc i e polyme [
10
]. Fu he mo e, he ques ion o he
sus ainabili y o he p oduc ion, ca bon oo p in , and ecyclabili y o hese new ma e ials
is open.
G aphene and i s de i a es show p omising EMI shielding p ope ies [
11
–
13
]. De ec -
ee single-laye g aphene shows an EMI shielding e iciency (SE) o 2.27 dB [
14
], while
ew-laye ed g aphene, g aphene doped wi h mo e elec onega i e a oms, and mul ilaye
ilm made o small and la ge g aphene lakes show he abili y o block 99% o he inciden
elec omagne ic wa e [
11
,
15
–
18
]. The main shielding mechanism o g aphene is abso p-
ion [
14
], which is a desi able shielding mechanism compa ed o ma e ials ha e lec
EMWs, such as me als, which cause seconda y pollu ion [
19
]. Apa om elec ical conduc-
i i y, bo h high dielec ic loss and low densi y make g aphene a e y a o able ma e ial as
an EMW abso be , while a de i a e o g aphene, g aphene oxide (GO), possesses oxygen
unc ional g oups ha induce s ong dipola pola iza ion and in e acial pola iza ion, im-
p o ing mic owa e a enua ion a GHz equencies [
20
]. Composi es based on g aphene
and i s de i a es block EMWs by abso p ion, e lec ion, and mul iple e lec ions [21,22].
Combining g aphene o g aphene oxide wi h a me al-based nanos uc u e such as
sil e nanowi es (AgNWs) enhances he conduc i i y and imp o es EMI SE, om 17 dB as
measu ed o educed g aphene oxide o 38 dB as ob ained o a composi e o g aphene
wi h AgNWs [
23
]. By adding AgNWs as a middle laye be ween wo educed g aphene
oxide laye s, Kuma e al. c ea ed a sandwich s uc u e, wi h an elec ical conduc i i y o
6.5
×
10
4
S m
−1
, able o block EMWs dominan ly by abso p ion o wa es [
23
]. Conside ing
ha me als a e e icien shielding ma e ials based mainly on EMW e lec ion, conduci e
g aphene-based composi es also show desi able EMI SE, wi h he ad an age ha he
shielding mechanism o en in ol es bo h e lec ion and abso p ion [22].
He ein, we in es iga ed he possibili y o ui biowas e usage as a s a ing ma e ial
in p oducing new, en i onmen - iendly EMI shielding ma e ials. The e o e, we selec ed
a side p oduc om he ui schnapps manu ac u ing p ocess. These byp oduc s a e
called dis ille y s illage. S illage is discha ged in la ge quan i ies by dis ille ies: o 1 L
o p oduced alcohol, be ween 8 and 15 L o s illage is gene a ed [
24
]. Due o high le els
o compounds wi h ni ogen and a ious o ganic molecules, hese was e ma e ials mus
be p ope ly managed, which demands addi ional cos s in he disposal o o ea men o
s illage [
25
,
26
]. One solu ion o s illage managemen is o p oduce e ilize o li es ock
eed, bo h low- alue p oduc s [
27
]. Recen ly de eloped echnology o eco e ing phenolic
acids has been epos ed, con ibu ing o mo e e icien s illage alo iza ion [28].
In his s udy, we used s illage collec ed a e dis illa ion o apple and quince schnapps
and py olyzed a 850
◦
C. We analyzed he s uc u al and mo phological p ope ies, as
well as he abili y o he ma e ials o block EMWs in he X-band equency egion. To
in es iga e he s uc u e o ca bonized ma e ials a bo h quali a i e and quan i a i e le els,
se e al spec oscopic echniques we e used: in a ed, Raman, ene gy-dispe si e X- ay,
X- ay pho oelec on spec oscopies, he mog a ime ic analysis, and BET su ace a ea
analyze . I was p e iously epo ed ha biocha p oduced om lignin inc eased he SE o
cemen [
29
], while sewage sludge biocha showed an SE alue >10 dB [
29
,
30
]. By explo ing
he possibili y o con e ing s illage in o alue-added, new, and highly demanded ma e ial,
his s udy aims o answe he need o hese new sus ainable p oduc s and gi e a new
pe spec i e on educing he en i onmen al bu den o s illage discha ge.
Nanoma e ials 2024,14, 1882 3 o 16
2. Ma e ials and Me hods
Samples o ca bonized biomass we e p oduced s a ing om esidual was e ma e ial
a e ui schnapps dis illa ion, i.e., dis ille y s illage. Two di e en ui schnapps esidual
dis ille y s illages we e used. Namely, esiduals om apples and quinces we e collec ed.
The dis ille y “Sk bic”, Nes in, Republic o Se bia, dona ed he s illages.
The expe imen al p ocedu e was conduc ed in he ollowing s ages:
1.
S illages we e i s dilu ed, using demine alized wa e p oduced by he Millipo e
Milli-Q
®
wa e sys em, Bu ling on, MA, USA. The olume a io o s illage o wa e
was 1:2.
2.
Dilu ed s illage was mechanically homogenized: he mix u es we e homogenized
mechanically using a ki chen choppe wi h a powe o 2000 W in 4 cycles o 15 min.
La ge pa icles and agmen s o he s a ing ma e ials ha could lead o inhomogene-
i y in he esul ing ma e ial we e emo ed by il a ion h ough il e pape .
3.
Homogenized, dilu ed s illage was il a ed: he esul ing solu ion was il e ed
h ough a Wha man Fil e Pape , G ade 4 (20–24
µ
m pa icle e en ion, Wha man
plc, Maids one, UK). The collec ed il a e was used o u he p oduc ion, while he
ma e ial le on he su ace o he il e pape was disca ded.
4.
D ying o he il a es: a e collec ing il a es, hey we e d ied a a mosphe ic p es-
su e a 85 ◦C. Consequen ly, black powde s we e ob ained.
5.
P e-ca boniza ion s ep: o achie e ca boniza ion, d ied biomass was mixed wi h KOH
( eagen g ade, 90%, lakes, Sigma Ald ich, S . Louis, MO, USA) in a mass a io o 1:1.
6. Ca boniza ion s ep: samples we e hea ed o 1 h a 850 ◦C in he s eam o N2.
7.
Cleaning s ep: a e ca boniza ion, he samples we e washed wi h demine alized
wa e o emo e KOH. Speci ically, black powde s ob ained a e ca boniza ion we e
imme sed in wa e . The powde s we e sepa a ed om wa e by simple decan a ion
a e clean wa e was added o he powde . The p ocedu e was epea ed un il he pH
was 7.
8.
A e KOH was emo ed, black powde s we e collec ed and d ied a 70
◦
C a a
educed p essu e.
The sample p oduced om esiduals ha emained a e e hanol dis illa ion in he
p ocess o apple schnapps p oduc ion was named BA, and he o he sample p oduced
om quince schnapps esiduals was named BQ. These powde s we e hen used o u he
analysis.
Raman spec a we e eco ded on a DXR Raman mic oscope (The mo Fishe Scien i ic,
Wal ham, MA, USA). Each spec um was ob ained a oom empe a u e using a 532 nm
exci a ion line wi h a powe o 2 mW. The da a we e analyzed h ough a spec ome e
equipped wi h 800 lines/mm ape u e and a 50
µ
m pinhole. The acquisi ion ime was
10 ×10 s.
Fo Fou ie - ans o m in a ed spec oscopy (FTIR) analysis, powde ed biomass sam-
ples we e mixed wi h KB and comp essed in o pelle s. FTIR spec a we e eco ded using
an FTIR Spec ome e (The mo Scien i ic Nicole iS20 FTIR Spec ome e , The mo Scien-
i ic™, Wal ham, MA, USA), in he ange o 4000–400 cm
−1
a 32 scans pe spec um and a
esolu ion o 4 cm−1.
The he mal s abili y o he BA and BQ samples was in es iga ed using a Me le
Toledo TGA/DSC 1 ins umen (Me le Toledo, Columbus, OH, USA). Pe each analysis,
a ound 3 mg o powde samples we e used. Samples we e hea ed om 40
◦
C o 750
◦
C a a
hea ing a e o 5 K min
−1
a a ni ogen low a e o 20 mL min
−1
. Each measu emen was
epea ed wo imes.
The s uc u al analysis o he syn hesized ma e ial was conduc ed using he X- ay
di ac ion (XRD) me hod by employing a Sma Lab
®
X- ay di ac ome e (Rigaku Co.,
Tokyo, Japan), wi h Cu K
α
adia ion a a con inuous scanning mode (40 kV, 30 mA, and
λ= 1.542 Å
). Measu emen s we e made in he a ious di ac ion angles anging om 6 o
35◦wi h a s ep size o 0.02◦and a measu emen speed o 2◦min−1.
Nanoma e ials 2024,14, 1882 4 o 16
Scanning elec on mic oscopy wi h an ene gy-dispe si e X- ay spec oscopy (SEM–
EDS) was pe o med on an INCAx-ac LN2- ee analy ical silicon d i de ec o o cha -
ac e is ic X- ays wi h he Pen aFET
®
P ecision and Az ec 4.3 so wa e package (Ox o d
Ins umen s, Ox o d, UK) connec ed o a TESCAN Mi a3 XMU (20 kV, SE de ec o , B no,
Czech Republic). Samples o py olyzed biomass we e deposi ed on double-sided conduc-
i e and adhesi e ype and we e analyzed.
To in es iga e he s uc u e o BA and BQ in de ail, X- ay Pho oelec on Spec oscopy
(XPS) was used. These measu emen s we e pe o med using a Physical Elec onics Indus-
ies PHI 5400 LS XPS (Physical Elec onics, Chanhassen, MN, USA) equipped wi h a 10-360
Sphe ical Capaci o Analyze (SCA). The SCA was se a ape u e 2 small, yielding an
analysis a ea o 600 mic ons. Aluminum K-alpha X- ays we e used as a sou ce. The powe
was se o 350 wa s. SCA pass ene gy was se o 178.95 eV. The eV/s ep was 0.250 eV.
Powde ed BA and BQ samples we e p essed on o Indium oil, which se ed as suppo .
The speci ic su ace a ea was ob ained by pe o ming ni ogen (N
2
) adso p ion. The
mesopo e and mic opo e olumes we e de e mined using he BJH and - es me hods, and
u ilizinga Quan ach ome au oso b TMiQ (Quan ach ome Ins umen s, Boyn on Beach, FL,
USA) su ace a ea analyze .
To in es iga e he shielding e iciency, BA and BQ powde s we e weighed and mixed
wi h a sodium silica e esin o p oduce a homogenous pas e. The concen a ion o p e-
pa ed BA and BQ pas es was 0.4 g mL
−1
(0.004 g/10
µ
L). BA and BQ pas es we e de-
posi ed on a 0.2 mm hick plexiglass shee co e ed wi h a pape mold and o med in o a
22.86 mm ×10.16 mm
hin ilm. The hickness o he ilms was also 0.2 mm, co esponding
o he hickness o he plexiglass shee . This size co esponds o he inne dimensions o
WR-90 wa eguide adap e s which we e used o he elec omagne ic shielding measu e-
men . The p epa ed ilms o BA and BQ samples a e shown in Figu e 1. The ansmission
coe icien s in he X-band (8–12 GHz equency ange) we e measu ed using a Rohde &
Schwa z ZVA 24 Vec o Ne wo k Analyze (VNA, Munich, Ge many).
− −
ff ff
α
λ ff
−
ffi
−
(a) (b)
Figu e 1. P epa ed ilms o BA (a) and BQ (b) samples.
The measu emen se up is shown in Figu e S1. I consis ed o wo WR90 wa eguide
adap e s connec ed o po s 1 and 2 o he VNA using RF coaxial cables. The hin ilm
o med was placed be ween he wo wa eguide adap e s and he S
21
sca e ing pa ame e
was measu ed o bo h ilms, as p e iously epo ed [31].
The shielding e ec i eness due o ansmission (SE
T
), Shielding E ec i eness due
o dissipa ion (SE
A
) and Shielding E ec i eness due o e lec ion (SE
R
) a e plo ed using
Equa ions (1)–(3):
SET=−S21 dB (1)
SER=−10log(1 −|S11|2) (2)
SEA=−10log(|S21|2/(1 −|S11|2)) (3)
Nanoma e ials 2024,14, 1882 5 o 16
whe e S
11
and S
21
ep esen he e lec ion and ansmission coe icien s, espec i ely, which
ha e been ob ained om he Vec o Ne wo k Analyze a e he measu emen o he
biomass samples.
3. Resul s and Discussion
To in es iga e he chemical composi ion, SEM–EDS analysis was ini ially pe o med.
Figu e 2shows SEM images o he py olyzed biomass samples. I can be obse ed ha
bo h BA and BQ a e homogeneous and ha e g anula mo phology.
ff ff
ff
−
− −
− −
ffi
Figu e 2. SEM images and associa ed EDS spec a o BA (a,b) and BQ (c,d), espec i ely.
Acco ding o EDS analysis (Figu e 2b,d and Table 1), he main chemical elemen s in
bo h samples a e C (77.82 o 75.66 w %) and O (13.90 and 16.49 w %), while o he elemen s,
such as Mg, Ca, Si, S, K, and Al, we e also de ec ed bu in e y small amoun s. The p esence
o oxic me als in biocha p o ides impo an in o ma ion o es ima ing he en i onmen al
impac o hese newly p oduced ma e ials [
32
]. EDS analysis shows ha Fe is p esen in
1.3 w % in BA, while o he hea y me als we e no de ec ed.
Table 1. Elemen al composi ion o BA and BQ samples in w % and a omic%.
BA BQ
Elemen w % A omic% Elemen w % A omic%
C 77.82 85.18 C 75.66 83.05
O 13.90 11.43 O 16.49 13.59
Mg 0.56 0.30 Mg 1.90 1.03
Al 0.48 0.24 Al 0.25 0.12
Si 4.21 1.97 Si 2.33 1.09
S 0.11 0.04 P 0.26 0.11
K 0.62 0.21 S 0.21 0.09
Ca 0.99 0.32 K 0.28 0.09
Fe 1.30 0.31 Ca 2.22 0.73
Nanoma e ials 2024,14, 1882 6 o 16
EDS maps we e ob ained o in es iga e homogenei y in e ms o chemical composi ion
(Figu e 3). These esul s indica ed an equal dis ibu ion o all de ec ed elemen s on he
su ace o bo h samples.
−
−
Figu e 3. SEM–EDS maps o BA (a,b) and BQ (c,d) o C, O, Si, Ca, and Mg.
FTIR spec oscopy was used o in es iga e he s uc u e o ca bonized biomass sam-
ples, and collec ed spec a a e p esen ed in Figu e 4. All spec a show he band a 3412 cm
−1
.
This band is assigned o OH g oups, a ached o hyd oxyl g oups o he ca bon skele on
o he ma e ial, o could be associa ed wi h physically abso bed wa e . Two low-in ensi y
bands a 2922 and 2851 cm
−1
a e also obse ed. These bands a e commonly obse ed in
FTIR spec a o a ious ca bon-based nanoma e ials, in g aphene oxide, g aphene quan-
um do s, and ca bon nano ubes [
33
,
34
], and s em om he asymme ic and symme ic
s e ching ib a ions o alkyl and alipha ic CH
2
bonds [
35
]. These bands a e p ominen in
he FTIR spec um o BQ bu could ha dly be obse ed in he BA spec um. This change
is associa ed wi h a lowe con en o me hyl g oups in he sample o BA [
36
]. All spec-
a show a p ominen band a 1570 cm
−1
esul ing om ib a ions o C=C bonds and
p o es he p esence o sp
2
domains in all samples. A low-in ensi y band a 1384 cm
−1
is
de ec ed and assigned o C-O bonds in COOH g oups. Addi ionally, wo bands a 1240
and 1110 cm
−1
a e associa ed wi h s e ching ib a ions o C-O bonds in epoxy and alkoxy
g oups, espec i ely [33,34].
Nanoma e ials 2024,14, 1882 7 o 16
−
−
−
− −
−
−
ff
−
Figu e 4. FTIR (a) and Raman (b) spec a o BA (black cu e) and BQ ( ed cu e).
Raman spec oscopy was used o in es iga e he s uc u e o BA and BQ samples,
and spec a a e p esen ed in Figu e 4b. The wo mos p ominen bands a e obse ed in
all spec a, one a 1349 cm
−1
and he second a 1585 cm
−1
. The i s band s ems om
de ec s in g aphi ic, sp
2
s uc u e due o g ain edges, a ious acancies, amo phous ca bon,
and unc ional g oups ha c ea e sp
3
si es [
37
–
39
]. This band is called he D-band and i s
in ensi y is associa ed wi h he le el o s uc u al diso de . The second band is called he
g aphi ic o G-band. This band s ems om he i s -o de sca e ing o he E
2g
phonon o
he bonds be ween sp
2
ca bon a oms [
40
]. The band a ound 2700 cm
−1
was also de ec ed.
This band is called G’ band o 2D which in ol es a wo-phonon double esonance Raman
sca e ing p ocess [
41
]. An addi ional low-in ensi y band could be no iced a 2875 cm
−1
.
This band is named he D + G band and is obse ed in o he g aphene samples p oduced
om biomass [
42
]. Applying he Knigh and Whi e equa ion [
43
], c ys alline size (La) was
calcula ed and i s alues a e p esen ed in Table 2. These calcula ions show ha an adequa e
size o he basal plane is simila o BA and BQ samples ob ained om di e en s a ing
ma e ials and compa able o GO p oduced using he modi ied Humme s me hod.
Table 2. Posi ion o G bands, ID/IG a ios, and c ys alline size (La) alues o BA and BQ.
Sample G Posi ion ID/IGLa = 4.4 (ID/IG)−1
BA 1583 0.96 4.58
BQ 1588 0.98 4.48
GO 1580 0.88–0.95 [34] 5.00
G aphi e 1575 0.04 [44] 110
Figu e 4a,b indica es ha BA and BQ possess bo h sp
2
and sp
3
C in hei s uc u e,
as well as a ious oxygen-con aining unc ional g oups, such as hyd oxyl, ca bonyl, and
ca boxyl.
Figu e 5a shows he TGA cu es o ca bonized biomass samples. Bo h TGA cu es
a e simila o p e iously obse ed he mog ams ob ained o ca bonized ice husks [
45
].
The py olysis p ocess is di ided in o h ee main phases: dehyd a ion, de ola iliza ion, and
ca boniza ion [
46
,
47
]. In he i s s age, up o 150
◦
C, a majo weigh loss o 21.08% o
BQ and 32.01% o BA was measu ed. This weigh loss is associa ed wi h he e apo a ion
o physically abso bed wa e , including inbound wa e [
48
]. Addi ionally, deg ada ion o
ola ile compounds wi h a small molecula weigh could also occu a his s age [
49
,
50
].
In he second s ep, in he empe a u e ange o 150–400
◦
C, he mino mass weigh s we e
measu ed: 3.80% o BQ and 6.27% o BA. In g aphene-based ma e ials, weigh loss in
his empe a u e ange is o en associa ed wi h he decomposi ion o oxygen-con aining
unc ional g oups, such as OH and epoxy g oups [
51
]. These weigh losses could be
Nanoma e ials 2024,14, 1882 8 o 16
associa ed wi h he decomposi ion o oxygen-con aining unc ional g oups, such as OH,
and epoxy g oups om he g aphi ic egions o ca bonized biomass [
52
–
54
]. As a hi d
s ep (in he empe a u e ange o 400–600
◦
C), weigh losses o 2.64% o BQ, and 2.73%
o BA we e measu ed. FTIR analysis showed he p esence o di e en oxygen-con aining
unc ional g oups, such as ca boxyl, ca bonyl, and hyd oxyl. I is assumed ha hese
g oups we e decomposed du ing s ages 2 and 3. Thus, he BQ sample showed less, while
BA showed signi ican ly la ge amoun s o he o al % o oxygen-con aining g oups. A
he inal s age, a 740
◦
C, he esidual sample weigh was 69.73% o BQ and 56.12% o
BA. These esul s indica e ha he BQ sample is e minally he mos s able wi h he lowes
con en o unc ional g oups.
ff
ff θ
ff
ff
Figu e 5. TGA cu es (a) and XRD pa e ns (b) o BA (black) and BQ ( ed).
XRD pa e ns o BA and BQ show wo di ac ion peaks in he 2
θ
ange o 25.5
◦
and
43.5
◦
(Figu e 5b). These bands co espond o di e en ypes o c ys alline g aphi e: (002)
and (100) planes, espec i ely [
55
,
56
]. No ably, he (002) la ice di ac ion peak pa e ns a e
mo e p onounced. These peaks sugges he o ma ion o he g aphi ic c ys alline s uc u e
du ing he ca boniza ion p ocess [
57
,
58
]. The highe in ensi y o he peaks a 25.5
◦
o BA
han in he BQ sample is ela ed o a highe -deg ee g aphi ic c ys alline s uc u e. Bo h
samples show a peak a 29.46
◦
assigned o he (104) plane o CaCO
3
[
59
]. The expe imen al
da a we e compa ed wi h he s anda d ICDD da abase (#00-005-0586). Elemen Ca was
obse ed in EDS spec a o BQ and BA samples, bu highe a and mass% was de ec ed
in BQ (Table 1), analogous o he in ensi y o he peak a 29.46
◦
in he XRD pa e n. The
s uc u e o ca bonized biomasses was in es iga ed using XPS and he esul s o hese
measu emen s a e displayed in Figu es 6and 7. Figu e 6shows su ey spec a and e eals
ha bo h samples con ain he ollowing elemen s: C, O, N, and In. The indium (In) p esence
in bo h spec a is due o he In oil being used as a sample suppo . The egions indica ed
by C1s, O1s, and N1s we e u he analyzed (see Figu e 7).
In bo h spec a, in he C 1s egion, h ee main con ibu ions we e iden i ied (
Figu e 7a,d
):
ca bon in C-C/C=C bonds a 284.8 eV and 284.6 eV, he C
−
O ca bon a ibu e o bo h epoxy
and hyd oxy g oups a 286.2 and 285.4 eV, and he C=O ca bon a 291.1 and 288.2 eV, in
BA and BQ spec a, espec i ely. Bonds iden i ied in he C 1s egion we e con i med by
inspec ion o he O 1s egion, whe e oxygen in single and double bonds we e iden i ied
in he BA spec um a 533.0 o C
−
O, and 531.9 a C=O eV, C-O,
∼
=
535.3 eV, and C=O,
∼
=532.8 eV in BQ. In C-O/C=O bonds, O was also de ec ed in ca bona es in bo h samples.
The egions indica ed by C1s, O1s, and N1s we e u he analyzed (see
Figu es 7and S2,
Supplemen a y Ma e ials). In bo h spec a, in he C 1s egion, h ee main con ibu ions
we e iden i ied (Figu e 7a,c): ca bon in C-C/C=C bonds, a 284.8 eV and 284.6 eV, he C
−
O
ca bon a ibu e o bo h epoxy and hyd oxy g oups, a 286.2 and 285.4 eV, and he C=O
ca bon a 291.1 and 288.2 eV, in BA and BQ spec a, espec i ely. Bonds iden i ied in he
C 1s egion we e con i med by inspec ion o he O 1s egion (Figu e 7b,d), whe e oxygen
in single and double bonds we e iden i ied in he BA spec um a 533.0 o C
−
O, and a
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