Effect of irrigation protocols on smear layer removal, bond strength and nanoleakage of fiber posts using a self-adhesive resin cement

Alessi Rodrigo Stadler,Jitumori Renata Terumi,Bittencourt Bruna Fortes,Gomes Giovana Mongruel,Gomes João Carlos 대한치과보존학회 2023 Restorative Dentistry & Endodontics Vol.48 No.3

Objectives This study aimed to investigate the effect of the application method of 2% chlorhexidine (CHX) and its influence on the adhesion of fiberglass posts cemented with a self-adhesive resin cement. Materials and Methods Sixty human mandibular premolars were endodontically treated and divided into 5 groups (n = 12), according to the canal irrigant and its application method: 2 groups with conventional syringe irrigation (CSI)—2.5% sodium hypochlorite (NaOCl) (control) and 2% CHX— and 3 groups with 2% CHX irrigation/activation—by passive ultrasonic irrigation (PUI), Easy Clean file, and XP-Endo Finisher file. Two roots per group were evaluated for smear layer (SL) removal by scanning electron microscopy. For other roots, fiber posts were luted using a self-adhesive resin cement. The roots were sectioned into 6 slices for push-out bond strength (BS) (7/group) and nanoleakage (NL) (3/group). Data from SL removal were submitted to Kruskal-Wallis and Student-Newman-Keuls tests (α = 0.05). Data from BS and NL were evaluated by 2-way analysis of variance and Tukey’s test (α = 0.05). Results For SL removal and BS, the CHX irrigation/activation promoted better values than CSI with CHX (p < 0.05), but it was not significantly different from CSI with NaOCl (p > 0.05). For NL, the lowest values were obtained by the chlorhexidine irrigation/activation groups (p < 0.05). Conclusions Active 2% CHX irrigation can be used to improve the post space cleaning and adhesion before fiber post cementation with self-adhesive resin cements. Objectives This study aimed to investigate the effect of the application method of 2% chlorhexidine (CHX) and its influence on the adhesion of fiberglass posts cemented with a self-adhesive resin cement. Materials and Methods Sixty human mandibular premolars were endodontically treated and divided into 5 groups (n = 12), according to the canal irrigant and its application method: 2 groups with conventional syringe irrigation (CSI)—2.5% sodium hypochlorite (NaOCl) (control) and 2% CHX— and 3 groups with 2% CHX irrigation/activation—by passive ultrasonic irrigation (PUI), Easy Clean file, and XP-Endo Finisher file. Two roots per group were evaluated for smear layer (SL) removal by scanning electron microscopy. For other roots, fiber posts were luted using a self-adhesive resin cement. The roots were sectioned into 6 slices for push-out bond strength (BS) (7/group) and nanoleakage (NL) (3/group). Data from SL removal were submitted to Kruskal-Wallis and Student-Newman-Keuls tests (α = 0.05). Data from BS and NL were evaluated by 2-way analysis of variance and Tukey’s test (α = 0.05). Results For SL removal and BS, the CHX irrigation/activation promoted better values than CSI with CHX (p < 0.05), but it was not significantly different from CSI with NaOCl (p > 0.05). For NL, the lowest values were obtained by the chlorhexidine irrigation/activation groups (p < 0.05). Conclusions Active 2% CHX irrigation can be used to improve the post space cleaning and adhesion before fiber post cementation with self-adhesive resin cements.

Dynamic analysis of piezoelectric perforated cantilever bimorph energy harvester via finite element analysis

Yousef A. Alessi,Ibrahim Ali,Mashhour A. Alazwari,Khalid Almitani,Alaa A Abdelrahman,Mohamed A. Eltaher Techno-Press 2023 Advances in aircraft and spacecraft science Vol.10 No.2

This article presents a numerical analysis to investigate the natural frequencies and harmonic response of a perforated cantilever beam attached to two layers of piezoelectric materials by using the finite element method for the first time. The bimorph piezoelectric is composed of 3 layers; two of them at the outer are piezoelectric, and the inner isotropic material. A higher order 3-D 20-node solid element that exhibits quadratic displacement behavior is exploited to discretize the isotropic layer, and coupled piezoelectric 3D element with twenty nodes is used to mesh the top and bottom layers. CIRCU94 element is added to act as a resistor part of the model. The proposed model is validated with previous works. The numerical parametric studies are presented to illustrate the effects of perforation geometry, the number of rows, the resistance on the natural frequencies, frequency response, and power. It is found that the thickness has a positive relationship with the natural frequency. Perforations help in producing higher voltage, and the best shape is rectangular perforations, and to produce higher voltage, two rows of rectangular perforations should be applied.

Biochar as a replacement material in advanced separation technologies

Daniel S. Alessi 대한환경공학회 2019 대한환경공학회 학술발표논문집 Vol.2019 No.-

Mechanisms of antimony adsorption onto soybean stover-derived biochar in aqueous solutions

Vithanage, M.,Rajapaksha, A.U.,Ahmad, M.,Uchimiya, M.,Dou, X.,Alessi, D.S.,Ok, Y.S. Academic Press 2015 Journal of environmental management Vol.151 No.-

Limited mechanistic knowledge is available on the interaction of biochar with trace elements (Sb and As) that exist predominantly as oxoanions. Soybean stover biochars were produced at 300 <SUP>o</SUP>C (SBC300) and 700 <SUP>o</SUP>C (SBC700), and characterized by BET, Boehm titration, FT-IR, NMR and Raman spectroscopy. Bound protons were quantified by potentiometric titration, and two acidic sites were used to model biochar by the surface complexation modeling based on Boehm titration and NMR observations. The zero point of charge was observed at pH 7.20 and 7.75 for SBC300 and SBC700, respectively. Neither antimonate (Sb(V)) nor antimonite (Sb(III)) showed ionic strength dependency (0.1, 0.01 and 0.001 M NaNO<SUB>3</SUB>), indicating inner sphere complexation. Greater adsorption of Sb(III) and Sb(V) was observed for SBC300 having higher -OH content than SBC700. Sb(III) removal (85%) was greater than Sb(V) removal (68%). Maximum adsorption density for Sb(III) was calculated as 1.88 x 10<SUP>-6</SUP> mol m<SUP>-2</SUP>. The Triple Layer Model (TLM) successfully described surface complexation of Sb onto soybean stover-derived biochar at pH 4-9, and suggested the formation of monodentate mononuclear and binuclear complexes. Spectroscopic investigations by Raman, FT-IR and XPS further confirmed strong chemisorptive binding of Sb to biochar surfaces.

Selection criteria for oxidation method in total organic carbon measurement

Yoon, GeunSeok,Park, Sang-Min,Yang, Heuiwon,Tsang, Daniel C.W.,Alessi, Daniel S.,Baek, Kitae Elsevier 2018 CHEMOSPHERE - Vol.199 No.-

<P><B>Abstract</B></P> <P>During the measurement of total organic carbon (TOC), dissolved organic carbon is converted into CO<SUB>2</SUB> by using high temperature combustion (HTC) or wet chemical oxidation (WCO). However, the criteria for selecting the oxidation methods are not clear. In this study, the chemical structures of organic material were considered as a key factor to select the oxidation method used. Most non-degradable organic compounds showed a similar oxidation efficiency in both methods, including natural organic compounds, dyes, and pharmaceuticals, and thus both methods are appropriate to measure TOC in waters containing these compounds. However, only a fraction of the carbon in the halogenated compounds (perfluorooctanoic acid and trifluoroacetic acid) were oxidized using WCO, resulting in measured TOC values that are considerably lower than those determined by HTC. This result is likely due to the electronegativity of halogen elements which inhibits the approach of electron-rich sulfate radicals in the WCO, and the higher bond strength of carbon-halogen pairs as compared to carbon-hydrogen bonds, which results in a lower degree of oxidation of the compounds. Our results indicate that WCO could be used to oxidize most organic compounds, but may not be appropriate to quantify TOC in organic carbon pools that contain certain halogenated compounds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Concentration of organic matter is not suitable to determine oxidation method. </LI> <LI> Chemical structure is a key factor determining oxidation of organic matter. </LI> <LI> Wet chemical oxidation oxidized partially halogenated compounds. </LI> </UL> </P>

Removal of hexavalent chromium in aqueous solutions using biochar: Chemical and spectroscopic investigations

Rajapaksha, Anushka Upamali,Alam, Md. Samrat,Chen, Ning,Alessi, Daniel S.,Igalavithana, Avanthi Deshani,Tsang, Daniel C.W.,Ok, Yong Sik Elsevier BV 2018 Science of the Total Environment Vol.625 No.-

<P><B>Abstract</B></P> <P>Biochar is an emerging low-cost sorbent used for removing trace metals from water. In this study, we evaluated the removal potential of aqueous hexavalent chromium (Cr(VI)) by biochars produced from soybean (<I>Glycine</I> <I>max</I> L.) and burcucumber (<I>Sicyos angulatus</I> L.) residues. The highest Cr(VI) removal from solution occurred at low pH values (pH2–5), and adsorption decreased approximately tenfold when the pH increased from 2 to 10. Synchrotron-based X-ray absorption spectroscopy (XAS) investigations showed that Cr(VI) species were reduced to trivalent chromium (Cr(III)) at the biochar surface following Cr(VI) adsorption. Linear combination fitting (LCF) of X-ray absorption near edge structure (XANES) data indicated that approximately 90% of the total Cr(VI) (962μM) was reduced to Cr(III). Extended X-ray absorption fine structure (EXAFS) fitting results yielded interatomic chromium (CrCr) distances consistent with the formation of Cr(III) precipitates as Cr(OH)<SUB>3</SUB>. Trivalent chromium is far less soluble than Cr(VI) and typically precipitates as amorphous Cr(III) solids. Thus, biochars produced by soybean and burcucumber residues are a promising technique for both adsorbing and reductively immobilizing Cr(VI) from aqueous solutions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Removal potential of aqueous Cr(VI) by biochar was evaluated. </LI> <LI> The highest Cr(VI) removal occurred at low pH values. </LI> <LI> Cr(VI) species can be reduced to Cr(III) at the biochar surface. </LI> <LI> Biochar properties determine the coordination environment of Cr(III) products. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Stability of heavy metals in soil washing residue with and without biochar addition under accelerated ageing

Shen, Zhengtao,Hou, Deyi,Zhao, Bin,Xu, Wendi,Ok, Yong Sik,Bolan, Nanthi S.,Alessi, Daniel S. Elsevier 2018 Science of the Total Environment Vol.619 No.-

<P><B>Abstract</B></P> <P>Soil washing residue (SWR), which typically concentrates the washed toxic metals and is comprised of high contents of clay particles, may pose risks to the surrounding environment. This study aims to simulate accelerated ageing to assess the stability of selected metals (Cd<SUP>2+</SUP> (132mg/kg), Cu<SUP>2+</SUP> (248mg/kg) and Pb<SUP>2+</SUP> (3470mg/kg)) in a SWR (89.68% of clay) with and without biochar treatment. The soil was incubated under constant moisture and wet-dry cycles (accelerated ageing), respectively, and the mobility and fractions of heavy metals in the soils with and without biochar treatment were examined. Under the constant moisture condition, biochar addition at 5% w/w reduced the leached Cd<SUP>2+</SUP> (by 1.81%) and Cu<SUP>2+</SUP> (by 8.70%) from SWR at day 1 and the leached Cu<SUP>2+</SUP> (by 51.08%) and Pb<SUP>2+</SUP> (by 25.36%) from SWR at day 14; however, the leached metals in the TCLP solution from the biochar-amended soils still exceed the regulatory limits (1mg/L for Cd<SUP>2+</SUP>, 5mg/L for Pb<SUP>2+</SUP>, no regulatory limits for Cu<SUP>2+</SUP>). Conversely, accelerated ageing (14days) significantly increased the fractions of exchangeable Cd<SUP>2+</SUP> (from 3.63–3.94% to 6.21–6.29%) and Pb<SUP>2+</SUP> (from 0.025–0.027% to 0.034–0.041%) as well as the TCLP leachabilities of Cd<SUP>2+</SUP> (from 2.91–3.28% to 3.46–3.73%), Cu<SUP>2+</SUP> (from 0.08–0.10% to 0.03–0.06%) and Pb<SUP>2+</SUP> (from 0.25–0.35% to 0.52–0.57%) in the soils, as compared with those incubated under constant moisture, regardless of biochar addition. This study reveals challenges associated with stabilising SWR due to the presence of residual fine-grained particles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cd<SUP>2+</SUP> and Pb<SUP>2+</SUP> in soil washing residue (SWR) exceeds TCLP regulation limit. </LI> <LI> Heavy metal mobility in SWR was reduced by biochar addition. </LI> <LI> Accelerated ageing mobilised heavy metals in SWR regardless of biochar addition. </LI> <LI> Accelerated ageing show SWR poses long-term risks to the environment. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of dissolved organic carbon from sludge, Rice straw and spent coffee ground biochar on the mobility of arsenic in soil

Kim, Hye-Bin,Kim, Seon-Hee,Jeon, Eun-Ki,Kim, Do-Hyung,Tsang, Daniel C.W.,Alessi, Daniel S.,Kwon, Eilhann E.,Baek, Kitae Elsevier 2018 The Science of the total environment Vol.636 No.-

<P><B>Abstract</B></P> <P>To date, studies on the mobility of arsenic (As) in soil amended with biochar have primarily relied on broad empirical observations, resulting in a gap between the behavior of As in amended soil and the chemical mechanisms controlling that behavior. This study focuses on the influence of abiotic factors in As mobility in As-contaminated soils amended with biochar. In order to understand the leaching of DOC and phosphate across a range of biomass feedstock and pyrolysis temperature, rice straw and granular sludge from an anaerobic digester were pyrolyzed at 300, 550, and 700 °C, and subjected to leaching studies by mixing air dried soil with 10 wt% of biochar at a soil: water ratio of 1:1(w/v). The concentration of DOC in the presence of granular sludge biochar and rice straw biochar increased from 190 mg L<SUP>−1</SUP> to 2605 mg L<SUP>−1</SUP> and 1192 mg L<SUP>−1</SUP>, respectively, which considerable accelerated the mobilization of Fe and As. More specifically, DOC drove the reduction of Fe(III) to Fe(II). Our results suggest enhanced release of As via the reductive dissolution of iron oxides, including by the chelating-enhanced dissolution of Fe oxides, and competitive desorption by DOC and phosphate from biochar. The influence of DOC and phosphate was further evaluated using realistic application amounts (1, 3, and 5 wt%) of biochars derived from pyrolysis of granular sludge, rice straw and spent coffee ground at 300 and 550 °C. The results from these experiments further confirm that DOC is a key factor for influencing the mobility of As in the amendment of biochar to As-contaminated soil, which indicates that biochar having low levels of leachable carbon should be amended to As-contaminated soils, and with caution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dissolved organic carbon from biochar increased mobility of As in soil. </LI> <LI> Biochar enhanced reductive dissolution of Fe oxides in soil. </LI> <LI> Dissolved organic carbons extract Fe via chelating enhanced dissolution. </LI> <LI> Phosphate enhanced As mobility via competitive desorption </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Modified sequential extraction for biochar and petroleum coke: Metal release potential and its environmental implications

von Gunten, Konstantin,Alam, Md. Samrat,Hubmann, Magdalena,Ok, Yong Sik,Konhauser, Kurt O.,Alessi, Daniel S. Elsevier 2017 Bioresource technology Vol.236 No.-

<P><B>Abstract</B></P> <P>A modified Community Bureau of Reference (CBR) sequential extraction method was tested to assess the composition of untreated pyrogenic carbon (biochar) and oil sands petroleum coke. Wood biochar samples were found to contain lower concentrations of metals, but had higher fractions of easily mobilized alkaline earth and transition metals. Sewage sludge biochar was determined to be less recalcitrant and had higher total metal concentrations, with most of the metals found in the more resilient extraction fractions (oxidizable, residual). Petroleum coke was the most stable material, with a similar metal distribution pattern as the sewage sludge biochar. The applied sequential extraction method represents a suitable technique to recover metals from these materials, and is a valuable tool in understanding the metal retaining and leaching capability of various biochar types and carbonaceous petroleum coke samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Modified four step sequential extraction method suitable for pyrolyzed materials. </LI> <LI> Untreated biochar may easily release alkaline earth and transition metals. </LI> <LI> Wood biochar releases metals more readily than does sewage sludge biochar. </LI> </UL> </P>

Risk evaluation of biochars produced from Cd-contaminated rice straw and optimization of its production for Cd removal

Shen, Zhengtao,Fan, Xiaoliang,Hou, Deyi,Jin, Fei,O'Connor, David,Tsang, Daniel C.W.,Ok, Yong Sik,Alessi, Daniel S. Pergamon Press 2019 Chemosphere Vol. No.

<P><B>Abstract</B></P> <P>Based on the “waste-treat-waste” concept, biochars were produced from cadmium (Cd)-contaminated rice straw (CRSBs) at 300, 500, and 700 °C (CRSB300, CRSB500, and CRSB700). The risks of the Cd remaining in CRSBs were evaluated and the optimal biochar pyrolysis temperature for Cd removal was investigated. It was observed that 41% of the total Cd in the raw rice straw was exchangeable, which may pose significant risks to crops and humans. Pyrolyzing at 300 °C did not significantly alter the Cd fractions, while the exchangeable fraction of Cd greatly dropped to 5.79% at 500 °C and further to 2.12% at 700 °C. Increasing the highest pyrolysis temperature resulted in CRSBs with higher pH values, greater surface area, and smaller pore sizes, thus providing more rapid and efficient removal of Cd from aqueous solutions. For Cd removal tests, increasing pyrolysis temperature (300–700 °C) increased the total (24.8–55.1 mg/g) and non-exchangeable (18.9–52.8 mg/g) Cd concentrations immobilized on the CRSBs and significantly decreased the exchangeable Cd fraction (23.7%–4.85%). It is suggested based on the study from aqueous solutions that CRSB700 was the most suitable for the remediation of Cd contaminated soil on site due to the lowest risks of remained Cd from feedstock, fastest and highest Cd removal, and most stable immobilization of Cd.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 41% of Cd in raw rice straw was exchangeable, posing great environmental risks. </LI> <LI> Pyrolyzing at 300 °C did not significantly alter Cd fractions remained in biochar. </LI> <LI> Exchangeable fraction of Cd dropped to 5.79% at 500 °C and to 2.12% at 700 °C. </LI> <LI> Increasing temperature decreased exchangeable Cd fraction immobilized on biochar. </LI> <LI> CRSB700 has the fastest and highest Cd removal, and most stable Cd immobilization. </LI> </UL> </P>