Release Of Hydroxyl Ions Research Articles

The Efficacy of Aloe vera Against Enterococcus faecalis as an Intracanal Medicament: A Systematic Review and Meta-Analysis.

Calcium hydroxide (CaOH) is commonly used as an intracanal medicament due to its antimicrobial properties; its antibacterial property depends on the release of hydroxyl ions. By analyzing experimental in vitro studies related to the research question, many studies carried out bacterial inoculation on extracted human teeth or laboratory Petri dishes.This review article seeks to assess the antimicrobial efficacy of Aloe vera (AV) againstEnterococcus faecalisin comparison to CaOH as an intracanal medicament.After being retrieved from databases such as PubMed, Scopus, the Cochrane Library, and EBSCOhost, publications from 2013 to 2024 were screened against our inclusion criteria. As a result, seven papers were included in the systematic review and four in the meta-analysis. Using a meta-analysis (Stata software version 16.0, StataCorp LLC, College Station, TX) to compare colony-forming units (CFUs) formed by CaOHand AV, forest plots were created to record the specimen size, mean, and standard deviation value of the outcome in CFU, at 95% confidence intervals. AV exhibits bactericidal qualities that are equal to or comparable to those of CaOH. AV displayed a nonsignificantly reduced CFU count than CaOH in a meta-analysis (p > 0.05). In summary, AV exhibits antibacterial/antimicrobial capabilities against E. faecalis that are equal to or comparable to CaOH.

Comparative Analysis of Calcium and Hydroxyl Ion Release from Pulp Dressing Materials in Pulpotomized Premolars.

BACKGROUND The aim of this study was to evaluate the time-dependent release of calcium (Ca⁺⁺) and hydroxyl (OH⁻) ions from 3 different pulp dressing materials used to cap root canal orifices in pulpotomized premolars. MATERIAL AND METHODS Freshly extracted (n=40) premolars were subjected to standardized pulpotomy procedure and finally restored in 5 groups using resin-modified glass ionmmer liner (RMGI) and bonded resin composite directly against the pulp chamber's floor (Control, G2) and over 3 different orifices' capping materials - Dycal (G3), Endo Sequence root repair material (ESRRM, G4), and mineral trioxide aggregate (MTA) Angelus (G5). Another 10 sound premolars served as the Reference group (G1). The restored teeth were incubated at 37±1°C in sealed containers filled with deionized water to assess Ca⁺⁺ and OH⁻ ions release after 24 h and at 1, 4, and 8 weeks. Two-way ANOVA and Tukey's comparisons at alpha=0.05 were used to statistically analyze the collected data. RESULTS Two-way ANOVA revealed significant differences in Ca⁺⁺ ions between test groups at different testing time intervals (P<0.05). Despite the constant (Tukey's, P<0.05) pH levels (OH⁻ release), Group 5 specimens exhibited higher Ca⁺⁺ ion release in comparison to Groups 4 and 3 at different testing timepoints (Tukey's, P<0.05). CONCLUSIONS Although all the assessed pulp dressing materials had equivalent and stable pH levels, ESRRM and MTA-Angelus had the highest Ca⁺⁺ ion release at the assessment intervals.

The sealing ability of different endodontic biomaterials as an intra-orifice barrier: evaluation with high-performance liquid chromatography.

This study evaluated the sealing ability of different biomaterials as intra-orifice barriers in the internal bleaching of discolored teeth with the walking bleaching technique. The release of hydroxyl ions from the bleaching materials can cause cervical root resorption, making it necessary to use intra-orifice barrier materials to prevent this issue. In the current study, the high-performance liquid chromatography (HPLC) method was used to measure the released hydroxyl ions. The study included 90 single-rooted and single-canal premolars, which were divided into four groups based on the intra-orifice barrier materials used (mineral trioxide aggregate [MTA], calcium-enriched mixture [CEM], Biodentine, and MTA+PG) and the type of bleaching material (sodium perborate + water or sodium perborate + hydrogen peroxide 30%). Two control groups were also considered in this study: a positive control group, where sodium perborate and hydrogen peroxide were placed inside the pulp chamber without any intra-orifice barriers; and a negative control group, where no bleaching agent or surgical obstruction was used, and the root surface was covered with wax up to the cemento-enamel junction (CEJ) level. The results showed that there was a significant difference in the concentration of hydroxyl ions released among the studied groups. The amount of hydroxyl ion released was highest in the positive control group and lowest in the CEM group. Among the intra-orifice barrier materials used, CEM cement was found to be the most appropriate material for use in the step-by-step internal bleaching method. The study highlights the importance of using appropriate intra-orifice barrier materials to prevent root cervical resorption in internal bleaching procedures.

Hydroxyl ion release ability from mixture of Indonesian White Portland Cements - Bi2O3 - Light Cured Methacrylate Based Resin as a Potential Pulp Capping Material

ABSTRACTIntroduction: The bioactivity property of pulp capping materials is determined by the hydroxyl ion release ability, which may alter the environmental pH to become alkaline. Calcium silicate-based materials are antibacterial, able to induce reparative dentin and have a good bacteria-tight seal. The poor handling of calcium silicate-based materials can be overcome by adding resin, so the materials will be easier to handle. Therefore, the purpose of this study was to synthesize a mixture of Indonesian White Portland Cements - Bi2O3 – UDMA and analyzed its hydroxyl ion release ability. Methods: The Indonesian White Portland Cements - Bi2O3 mixture was prepared using the simple solution method and mixed with UDMA. The sample’s ability to release hydroxyl ions was measured using a pH meter and titration test. Results: This study showed that the mixture of Indonesian White Portland Cements - Bi2O3 - UDMA had an initial pH of 11.04 and increased to its peak on 168 hours mark, or on day seven, to pH 11,77 with hydroxyl ion release value of 10-2.23 Conclusion: The mixture of Indonesian White Portland Cements - Bi2O3 -UDMA had an alkaline pH, was able to release hydroxyl ion and had a potential to be used as a pulp capping material.Keywords: The mixture Indonesia White Portland Cements - Bi2O3 – UDMA, Hydroxyl ion, Release Ability

An Overview of Antibacterial Dental Restorative Materials

Antibacterial dental restorative materials (ADRM) have been developed to prevent or treat dental caries and other infections. Glass ionomer cements (GICs), composite resins, calcium hydroxide-based materials, mineral trioxide aggregate (MTA), bioactive glasses, silver-containing materials, quaternary ammonium compounds (QACs), chlorhexidine, nanoparticles, and photodynamic therapy (PDT) are common types of ADRMs. They have antibacterial properties due to the release of fluoride ions, QACs, silver nanoparticles, calcium and hydroxyl ions. ADRMs can prevent tooth decay, promote healing of pulp tissue and regenerate damaged tissues. Researchers are exploring new agents like nanoparticles and antimicrobial peptides to improve the antibacterial properties of ADRMs. PDT is a promising technology for improving the antibacterial properties of dental restorative materials. Antibacterial bioactive dental materials like bioactive glasses, calcium phosphate-based materials, hydroxyapatite-based materials, antibacterial peptides, and silver-containing materials have been developed to provide an additional layer of protection against infection and improve the longevity of dental restorations.

Alkalizing Properties of Six Calcium-Silicate Endodontic Biomaterials.

Introduction: Calcium silicate-based cements (CSC), are self-setting hydraulic biomaterials widely used for reparative procedures in dentistry and endodontics. These materials possess physical properties, such as ion release, porosity, solubility, and radiopacity. Their biological properties are connected to their alkalizing activity and calcium release capacity. Materials and Methods: Six calcium silicate-based materials were selected for this study: TheraCal LC (Bisco Inc., Schaumburg, IL, USA), MTA Plus (PrevestDenpro, Jammu, India Avalon Biomed Inc., Bradenton, FL, USA), Biodentine (Septodont, Saint-Maur-des-Fossés, France), RetroMTA (BioMTA, Seoul, Korea), MTA Flow (Ultradent Products, Inc., South Jordan, UT, USA), and OrthoMTA (BioMTA, Seoul, Korea). The pH was analyzed immediately after immersion (baseline) and after 1 h, 3 h, 1 day, 2 days, 3 days, 1 week, 2 weeks, 3 weeks, and 1 year with a pH meter, previously calibrated with solutions of known pH. All testing materials had alkaline pH. Results: Analysis of the tested materials showed statistically significant differences in terms of pH changes as a function of the time showed a gradual rise in the pH of all materials. Conclusions: All tested materials exhibited continuous hydroxyl ion release resulting in a rise in pH until the end of time of experience.

Sealing ability of mineral trioxide aggregate, Biodentine, and EndoSequence RRM putty used as retrograde restorative material: An in vitro bacterial leakage model study

Sealing ability of mineral trioxide aggregate, Biodentine, and EndoSequence RRM putty used as retrograde restorative material: An in vitro bacterial leakage model study

Comparison of calcium and hydroxyl ion release ability and in vivo apatite-forming ability of three bioceramic-containing root canal sealers.

Bioceramic-containing root canal sealers promote periapical healing via Ca2+ and OH- release and apatite formation on the surface. This study aimed to compare Ca2+ and OH- release and in vivo apatite formation of three bioceramic-containing root canal sealers: EndoSequence BC sealer (Endo-BC), MTA Fillapex (MTA-F), and Nishika Canal Sealer BG (N-BG). Polytetrafluoroethylene tubes filled with sealers were immersed in distilled water for 6 and 12h and for 1, 7, 14, and 28days to measure Ca2+ and OH- release. Additionally, tubes filled with sealers were implanted in the backs of rats for 28days, and in vivo apatite formation was analyzed using an electron probe microanalyzer. Endo-BC released significantly more Ca2+ than the other sealers at 6 and 12h and 1day. Ca2+ release was significantly lower from N-BG than from Endo-BC and MTA-F at 14 and 28days. OH- release was significantly higher from Endo-BC than from the other sealers throughout the experiment, except at 1day. OH- release was lower from N-BG than from MTA-F at 6h and 7days. Only Endo-BC implants exhibited apatite-like calcium-, phosphorus-, oxygen-, and carbon-rich spherulites and apatite layer-like calcium- and phosphorus-rich, but radiopaque element-free, surface regions. Ca2+ and OH- release is ranked as follows: Endo-BC > MTA-F > N-BG. Only Endo-BC demonstrated in vivo apatite formation. Endo-BC could promote faster periapical healing than MTA-F and N-BG.

DNAzyme-based colorimetric assay and its application for lipopolysaccharide analysis assisted by oxime chemistry

Herein, for the first time, we propose that the cleavage activity of DNAzyme is accompanied by the release of hydroxyl ions, which can be used for colorimetric assay. Subsequently, we further construct a colorimetric strategy for lipopolysaccharide (LPS) analysis by using this property. Detailly, DNAzyme is split into two fragments separately modified with aldehyde group and hydroxylamine group, which can be linked together through oxime chemistry and the presence of LPS can prevent the formation of oxime bond. The formed whole DNAzyme can mediate the release of hydroxyl ions serving for colorimetric signal output. Taking LPS as model targets, DNAzyme-based colorimetric assay has been successfully constructed. This work not only provides a colorimetric strategy to analyze DNAzyme activity, but also gives a new insight to enrich the versatility of DNAzymes and to enhance their multifunctionality.

Comparative evaluation of diffused calcium and hydroxyl ion release from three different Indirect pulp capping agents in permanent teeth – An in vitro study

BackgroundIndirect pulp capping therapy has gained increased popularity in paediatric dentistry since it is less invasive, and is of low cost. The aim of the present study was to evaluate and to compare the diffusion of calcium (Ca2+) and hydroxyl (OH–) ions through coronal dentin into pulp after indirect pulp capping in vitro using TheraCal LC, ProRoot MTA and Calcimol LC. Materials and methodsTotal of 60 human caries-free maxillary first premolars were selected for the study. Samples were divided into 4 groups with 15 in each group: Group 1 TheraCal LC; Group 2 ProRoot MTA; Group 3 Calcimol LC; Group 4 Control Group. Indirect pulpcapping on the coronal RDT (remaining dentine thickness) system was performed using pulp-capping materials, such as TheraCal LC, ProRoot MTA and Calcimol LC, on the respective samples. The control group was completely filled with composite. Ca2+ ions (ppm) and OH– ions (pH) were analysed in deionized water using a multimeter connected to a calcium probe (calcium ion electrode) and pH metre connected to a temperature-compensated pH probe after 3 h, 24 h, 7 days, 14 days, 28 days and 60 days. ResultsCalcium release was significantly higher (P < 0.05) in the TheraCal LC group than in the other groups. Slightly alkaline pH values were observed in all the groups except for the control. ConclusionTheraCal is a new light-curable pulp capping material that initially releases high Ca2+ ions and creates an environmental pH close to physiological pH after 60 days.

Calcium Silicate-Based Biocompatible Light-Curable Dental Material for Dental Pulpal Complex.

Dental caries causes tooth defects and clinical treatment is essential. To prevent further damage and protect healthy teeth, appropriate dental material is a need. However, the biocompatibility of dental material is needed to secure the oral environment. For this purpose, biocompatible materials were investigated for incorporated with dental capping material. Among them, nanomaterials are applied to dental materials to enhance their chemical, mechanical, and biological properties. This research aimed to study the physicochemical and mechanical properties and biocompatibility of a recently introduced light-curable mineral trioxide aggregate (MTA)-like material without bisphenol A-glycidyl methacrylate (Bis-GMA). To overcome the compromised mechanical properties in the absence of Bis-GMA, silica nanoparticles were synthesized and blended with a dental polymer for the formation of a nano-network. This material was compared with a conventional light-curable MTA-like material that contains Bis-GMA. Investigation of the physiochemical properties followed ISO 4049. Hydroxyl and calcium ion release from the materials was measured over 21 days. The Vickers hardness test and three-point flexural strength test were used to assess the mechanical properties. Specimens were immersed in solutions that mimicked human body plasma for seven days, and surface characteristics were analyzed. Biological properties were assessed by cytotoxicity and biomineralization tests. There was no significant difference between the tested materials with respect to overall physicochemical properties and released calcium ions. The newly produced material released more calcium ions on the third day, but 14 days later, the other material containing Bis-GMA released higher levels of calcium ions. The microhardness was reduced in a low pH environment, and differences between the specimens were observed. The flexural strength of the newly developed material was significantly higher, and different surface morphologies were detected. The recently produced extract showed higher cell viability at an extract concentration of 100%, while mineralization was clear at the conventional concentration of 25%. No significant changes in the physical properties between Bis-GMA incorporate material and nanoparticle incorporate materials.

Evaluation of the diffusion of calcium hydroxide-based medicaments through the dentinal tubules and apical foramen: A mass spectrometry study.

Aims:This mass spectrometry study investigated the diffusion of hydroxyl and calcium ions from a calcium hydroxide intracanal medicament (Pulpdent®) when used alone or mixed in equal parts with a steroid–antibiotic paste (Ledermix®).Materials and Methods:The pH (using pH meter) and calcium ion concentration (using inductively coupled plasma-mass spectrometry) of the diffused medicaments were assessed using endodontically prepared human extracted teeth with either a sealed or a patent apex, at time intervals of 1, 3, 8, 24, and 168 h.Statistical Analysis:A one-way ANOVA was used to explore differences between and within groups, with Tukey–Kramer/Games–Howell posttests.Results:In both situations tested, Pulpdent® showed greater release of both calcium and hydroxyl ions than when mixed in equal parts with Ledermix®. Greater initial release of both ions occurred in roots with a patent apex, but by 1 week there was no significant difference between the two. If a 50:50 combination of Pulpdent® paste and Ledermix® paste is used, there is a lower release of calcium ions and hydroxyl ions than using Pulpdent® paste alone.Conclusion:With both Pulpdent® paste alone and Pulpdent® paste mixed equally with Ledermix® paste, the major pathway for movement of hydroxyl ions and calcium ions is diffusion through the dentine of the root, with the apex playing only a minor role.

Influence of exposure to phosphoric and polyacrylic acids on selected microscopic and physical/chemical properties of calcium hydroxide cements

This study aimed to evaluate if the contact of calcium hydroxide cements with polyacrylic and phosphoric acids would alter selected microscopic and physical and chemical properties. Chemically activated (Hydro C and Dycal Advanced Formula II) and resin-modified photoactivated (Ultra-blend Plus) calcium hydroxide cements were examined after exposure to the following different strategies: contact with no substance (control group); rinsing with water and drying; contact with polyacrylic acid, rinsing with water, and drying; and contact with phosphoric acid, rinsing with water, and drying. Surface morphology, determined by scanning electron microscopy (SEM), water sorption and solubility, and the release of hydroxyl ions were evaluated. SEM showed a greater impact of the conditioning acids on the surface of the chemically activated cements. Ultra-blend Plus obtained the highest value of sorption (516.8 μg/mm3) and solubility (381.1 μg/mm3) and Hydro C had the lowest values 251.9 μg/mm3 and 206.3 μg/mm3 respectively. Considering the release of hydroxyl ions in comparison with time, Hydro C and Ultra-blend Plus presented significant statistical difference for polyacrylic and phosphoric acid subgroups. Hydro C and Dycal presented intensification of surface irregularities after contact with conditioning acids. The chemically activated materials suffered a decrease in sorption and solubility. The action of the conditioning acids promotes greater increase of the release of hydroxyl ions for Hydro C and Dycal.

Silane modification of layered silicates and the mechanism of network formation from exfoliated layers

The edges of a synthetic layered silicate, Laponite XLG, was successfully modified with various amounts of ethoxytrimethylsilane, a monofunctional silane compound. The occurrence of the reaction was confirmed with various techniques. Thermogravimetric measurements and Fourier-transform infrared spectroscopy (FTIR) carried out on both the treated filler and the reaction medium yielded a saturation like correlation as a function of the amount of the silane used for treatment. The analysis of the bonded amount of silane by FTIR spectroscopy showed that a side reaction takes place during modification. Although the expected dimerization did not occur, the silane hydrolyzed, thus systematically changing the amount of bonded silane determined from the FTIR absorption of oxygen containing groups. Only vibrations related to the absorption of the SiCH3 group can be used for quantitative analysis. X-ray diffraction (XRD) measurements proved that the silane is bonded onto the surface of the silicate and it does not enter the interlamellar space. Approximately 50 mg silane is bonded to 1 g silicate corresponding to almost complete reaction of the surface OH groups. The results of the measurements were supported by model calculations and extremely good agreement was found between the calculated and the measured values. Surface modification did not hinder the formation of a house-of-card structure showing that the generally accepted mechanism of network formation needs revision. An explanation was offered based on the release of hydroxyl ions from the MgOH moiety of the silicate. The modification of the edges of layered silicates may facilitate exfoliation or help functionalization, but does not prevent network formation and cannot be used for the control of rheological properties.

Chitosan/gelatin as a new nano-carrier system for calcium hydroxide delivery in endodontic applications: Development, characterization and process optimization

The main aim of this study is preparation, optimization and in vitro characterization of Chitosan/Gelatin nano-carriers (NCs) for calcium hydroxide (CH) to improve its therapeutic potential. The designed system can be used in the endodontic applications demanding a sustained release of calcium and hydroxyl ions. Modeling and optimization of CH loaded polymeric NCs were performed using response surface methodology (RSM) based on central composite surface statistical design. The effect of Chitosan concentration (0.1–1% w/v), Gelatin concentration (0.1–1% w/v) and CH concentration (0.05–0.4% w/v) on the particle size, polydispersity index (PDI), drug loading (DL) and encapsulation efficiency (EE) of CH loaded polymeric NCs were investigated. Optimized CH loaded polymeric NCs formulation which obtained using RSM showed spherical and smooth surface with a particle size of 292 nm, PDI of 0.32, DL of 88.8% and EE of 99%. Optimized formulation was evaluated for in vitro calcium ion release in phosphate buffer solution (PBS) at pH 7.4 for 14 days. The presence of hydrogen bonding and some intermolecular interactions between Chitosan/Gelatin polymeric materials were confirmed using Fourier transform infrared (FTIR) analysis. These interactions enable Chitosan/Gelatin NCs to load CH and maintain sustained release of Calcium ions from CH during experimental period.

A comparison of hydroxyl ion diffusion through root dentine from various calcium hydroxide preparations.

Different calcium hydroxide [Ca(OH)2 ] formulations are available. The aim was to assess differences in hydroxyl ion release with different formulations. Sixty-six teeth were divided one control (n = 6) and four experimental (n = 15) groups: (i) Pulpdent Paste; (ii): DT Temporary Dressing; (iii): Ca(OH)2 powder/saline; (iv): Ca(OH)2 points; (v): no medicament. pH was measured in inner dentine and outer dentine cavities over 12 weeks. Inner dentine pH rose rapidly for all groups except the points and controls. Peak pH was reached by day 2 before dropping and stabilising (8.0-9.2). Outer dentine pH rose steadily until day 21 for aqueous solutions and then stabilised (8.0-8.5). The points had minimal pH increase for the entire period. There were no significant differences in hydroxyl ion release between the aqueous solutions. Type of paste base did not affect release and diffusion of hydroxyl ions which continued for 84 days.

IN VITRO BIO-INTERACTIVITY OF MTA MIXED WITH DIFFERENT ACCELERANT SOLUTIONS

Aim: To evaluate and compare the biointeractivity (calcium and hydroxyl ion release into the leachate) of mineral trioxide aggregate (MTA) mixed with three different accelerant solutions. Methods: MTA was mixed with 5% calcium chloride (Group CL), 15% disodium hydrogen orthophosphate (Group NaP), 0.1% citric acid (Group CA) or distilled water (Group DW) as control; each group comprised ten specimens (n=10). The specimens were prepared by packing the mixtures into plastic tubes, 1.5 mm in internal diameter and 10 mm in length. Each specimen was immersed in 10 ml deionized water. The calcium ion release and pH were measured in the leachate after 24, 72 and 168h of material immersion using an atomic absorption spectrophotometer and a digital pH-meter respectively. Data were analysed using 2-way analysis of variance (ANOVA) with repeated measures, 1-way ANOVA and Tukey post hoc test; p-values less than 0.05 indicated statistical significance (p<0.05). Results: The accelerant type and time significantly influenced both calcium ion release and pH (p 0.05). Group NaP showed the highest leachate pH compared to Group DW at all time points. In general, calcium ion release and pH decreased over the 168-hour duration. Conclusions: Within the conditions of this study, it could be concluded that, among the used MTA accelerants, 5% calcium chloride solution could yield the highest calcium ion release, while 15% disodium hydrogen orthophosphate solution may have the highest alkalizing activity; such accelerants could provide MTA with enhanced biointeractive qualities besides accelerating its setting.

Comparison of Commercial Calcium Hydroxide Pastes for Prolonged Antibacterial Effect using a Colourimetric Assessment.

The anti-microbial activity of calcium hydroxide pastes used in endodontics is dependent on establishing high levels of hydroxyl ions in dentine. This study investigated hydroxyl ion diffusion from different commercial calcium hydroxide pastes using a novel colourimetric method. In this method, human tooth roots were stained with anthocyanin dye, which changed their colour according to the local pH conditions. Prepared root canals were filled with pastes formulated with the vehicle of water (Pulpdent™, Calasept Plus™), polyethylene glycol (PEG) (Calmix™) or a mixture of water, PEG and ibuprofen (Odontocide™). The changes in dye colour at fixed distances from the canal wall were monitored using standardised digital photography over a period of 3 weeks. A repeated measures analysis tracked changes in each root from baseline. Release of hydroxyl ions varied between the different commercial compositions containing water or PEG as solvents. The colour changes in the dentine, due to released hydroxyl ions, were greatest and more prolonged for completely non-aqueous compositions, when using PEG 400 as the vehicle. When water was present in the product, the duration of the pH changes was shorter. This was attributed to the presence of hydroxyl ions in the water (the common-ion effect) and a more vigorous buffering of hydroxyl ions by dentine proteins.

Hydroxyl Ion Diffusion through Radicular Dentine When Calcium Hydroxide Is Used under Different Conditions.

Calcium hydroxide’s anti-bacterial action relies on high pH. The aim here was to investigate hydroxyl ion diffusion through dentine under different conditions. Teeth were divided into control (n = 4) and four experimental groups (n = 10): Group 1—no medicament; Group 2—Calmix; Group 3—Calmix/Ledermix; Group 4—Calasept Plus/Ledermix; Group 5—Pulpdent/smear layer. Deep (inner dentine) and shallow (outer dentine) cavities were cut into each root. pH was measured in these cavities for 12 weeks. The inner and outer dentine pH in Group 2 was significantly higher than all groups. Inner dentine pH in Group 3 was slightly higher than that in Group 4 initially but subsequently comparable. After Day 2, Group 5 had significantly lower pH than Groups 3 and 4. The outer dentine pH in Group 3 started higher than that in Groups 4 and 5, but by Day 28 the difference was insignificant. The time for the inner dentine to reach maximum pH was one week for Group 2 and four weeks for Groups 3 and 4. The time for the outer dentine to reach maximum pH was eight weeks for all experimental groups. Mixing different Ca(OH)2 formulations with Ledermix gave similar hydroxyl ion release but pH and total diffusion was lower than Ca(OH)2 alone. The smear layer inhibited diffusion.

Removal of metals from industrial wastewater and urban runoff by mineral and bio-based sorbents

The study was performed to evaluate chemically modified biosorbents, hydrochloric acid treated peat (HCl-P) and citric acid treated sawdust (Citric acid-SD) for their metal removal capacity from dilute industrial wastewater and urban runoff and compare their efficiency with that of commercially available mineral sorbents (AQM PalPower M10 and AQM PalPower T5M5 magnetite). Batch and column experiments were conducted using real water samples to assess the sorbents' metal sorption capacity. AQM PalPower M10 (consisting mainly of magnesium, iron and silicon oxides) exhibited excellent Zn removal from both industrial wastewater and spiked runoff water samples even at low dosages (0.1 g/L and 0.05 g/L, respectively). The high degree of Zn removal was associated with the release of hydroxyl ions from the sorbent and subsequent precipitation of zinc hydroxide. The biosorbents removed Ni and Cr better than AQM PalPower M10 from industrial wastewater and performed well in removing Cr and Cu from spiked runoff water, although at higher dosages (0.3–0.75 g/L). The main mechanism of sorption by biosorbents was ion exchange. The sorbents required a short contact time to reach equilibrium (15–30 min) in both tested water samples. AQM PalPower T5M5 magnetite was the worst performing sorbent, leaching Zn into both industrial and runoff water and Ni into runoff water. Column tests revealed that both HCl-P and AQM PalPower M10 were able to remove metals, although some leaching was witnessed, especially As from AQM PalPower M10. The low hydraulic conductivity observed for HCl-P may restrict the possibilities of using such small particle size peat material in a filter-type passive system.