Influence of different carbon monolith preparation parameters on pesticide adsorption

The capacity of carbon monolith for pesticide removal from water, and the mechanism of pesticide interaction with carbon surface were examined. Different carbon monolith samples were obtained by varying the carbonization and activation parameters. In order to examine the role of surface oxygen groups in pesticide adsorption, carbon monolith surface was functionalized by chemical treatment in HNO3, H2O2 and KOH. The surface properties of the obtained samples were investigated by BET surface area, pore size distribution and temperature-programmed desorption. Adsorption of pesticides from aqueous solution onto activated carbon monolith samples was studied by using five pesticides belonging to different chemical groups (acetamiprid, dimethoate, nicosulfuron, carbofuran and atrazine). Presented results show that higher temperature of carbonization and the amount of activating agent allow obtaining microporous carbon monolith with higher amount of surface functional groups. Adsorption properties of the activated carbon monolith were more readily affected by the amount of the surface functional groups than by specific surface area. Results obtained by carbon monolith functionalisation showed that π-π interactions were the main force for adsorption of pesticides with aromatic structure, while acidic groups play an important role in adsorption of pesticides with no aromatic ring in the chemical structure

Uklanjanje olova i kadmijuma iz vodenog rastvora koristeći okrakalcijum-fosfat kao adsorbent

Octacalcium phosphate (OCP) is a material from the calcium phos-phate group with a crystal structure similar to hydroxyapatite. The removal process of lead and cadmium in aqueous solution using octacalcium phosphate material was investigated. OCP material was synthesized by the solution pre-cipitation method. The structural and phase properties of OCP before and after the removal process were determined by the X-ray diffraction (XRD) method. Microstructural and semi-quantitative analysis of the material was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS). Characteristic bands and functional group determination were revealed using the Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR). As target pollutants, Cd(II) and Pb(II) were chosen in adsorption experiments. Results show that OCP in the first 10 min has a very fast removal rate for Pb(II); the equilibrium state was reached after 10 min with more than 98 % adsorption efficiency. Results for Cd(II), results showed the same removal rate but somewhat lower adsorption efficiency, amounted to approximately 63 %

Nanoemulsification synthesis route for obtaining highly efficient Ag3PO4 photocatalytic nanomaterial

Nanoemulsion technique based on Ouzo effect was applied for the fast and simple synthesis of Ag3PO4 at room temperature. X-ray powder diffraction analysis and Raman spectroscopy reviled that synthesized powder was single-phase. Using scanning electron microscopy analysis, it was found that the synthesized Ag3PO4 particles were near-spherical shape with an average diameter of 100 nm. The high value for the specific surface area of obtained powder was measured by Brunauer–Emmet–Teller method. Finally, the Ag3PO4 product was used as a photocatalyst for the photodegradation of crystal violet dye in an aqueous solution. Nanoemulsion strategy procedure provides a simple pathway to obtain a highly efficient single-phase Ag3PO4 photocatalyst

Hydroxyapatite/TiO2 Nanomaterial with Defined Microstructural and Good Antimicrobial Properties

Due to the growing number of people infected with the new coronavirus globally, which weakens immunity, there has been an increase in bacterial infections. Hence, knowledge about simple and low-cost synthesis methods of materials with good structural and antimicrobial properties is of great importance. A material obtained through the combination of a nanoscale hydroxyapatite material (with good biocompatibility) and titanium dioxide (with good degradation properties of organic molecules) can absorb and decompose bacteria. In this investigation, three different synthesis routes used to prepare hydroxyapatite/titanium dioxide nanomaterials are examined. The morphology and semiquantitative chemical composition are characterized by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX). The obtained materials’ phase and structural characterization are determined using the X-ray powder diffraction method (XRD). The crystallite sizes of the obtained materials are in the range of 8 nm to 15 nm. Based on XRD peak positions, the hexagonal hydroxyapatite phases are formed in all samples along with TiO2 anatase and rutile phases. According to SEM and TEM analyses, the morphology of the prepared samples differs depending on the synthesis route. The EDX analysis confirmed the presence of Ti, Ca, P, and O in the obtained materials. The IR spectroscopy verified the vibration bands characteristic for HAp and titanium. The investigated materials show excellent antimicrobial and photocatalytic properties

HEMP FIBERS AGAIN IN SERBIA: OLD FIBERS – NEW APPLICATIONS

This paper attempts to summarize the historical facts about the cultivation and use of hemp in the world, and especially in Serbia, with a special emphasis on the research and new application brought by the renaissance of hemp production at the end of the 20th century. Hemp (Cannabis Sativa L.) as one of the oldest cultivated plants represents a renewable and sustainable source of fibers, mainly for textile production. Due to their specific chemical composition, structure and properties, such as high specific strength, non-toxic, biocompatible and biodegradable nature, hemp fibers become ideal candidates for a wide range of applications. Being lignocellulosic, hemp can be used alone, or as combined with different kinds of polymers to provide a wide range of useful composites in textiles, construction, automotive industry, and soil conservation. Also, hemp fibers have proven to be efficient biosorbents and suitable precursors for the production of low-cost carbon materials for adsorption applications.U ovom radu su sumirane istorijske činjenice o gajenju i upotrebi konoplje u Srbiji i svetu, sa posebnim osvrtom na istraživanja i nove primene sa renesansom konoplje krajem 20. veka. Konoplja (Canabis Sativa L) je jedna od najstarijih gajenih biljaka, i predstavlja obnovljiv i održiv izvor vlakana, uglavnom za tekstilnu industriju. Zbog svog specifičnog hemijskog sastava, strukture i svojstava, kao što su visoka specifična čvrstoća, netoksičnost, biokompatibilnost i biorazgradivost, vlakna konoplje imaju visok potencijal za primenu u različitim oblastima. Sama, ili kao kompozit u kombinaciji sa različitim vrstama polimera, konoplja nalazi primenu u oblastima tekstila, građevinarstva, automobilske industrije, očuvanja životne sredine. Takođe, vlakna konoplje su se pokazala kao efikasni biosorbenti i pogodni prekursori za proizvodnju jeftinih ugljeničnih adsorbenata za prečišćavanje vode od organskih i neorganskih zagađujućih materija

The effect of boron doping on the structure and properties of carbonized hydrothermal carbon

Structural and surface characterization of pristine and boron doped carbonized hydrothermal carbons (CHTC) is reported. Boron was introduced into glucose precursor solution with concentration of 0.2% and 1%. Following hydrothermal treatment, samples were carbonized to 1000oC and examined by Raman spectroscopy and temperature programmed desorption. Characterization of obtained samples as material for carbon paste electrode was performed by cyclic voltammetry measurements of the Fe (CN)6 3-/4- redox couple. Structural analysis showed that lower boron content in precursor solution induced structure ordering, while higher amount of boron caused structural disorder of CHTC sample. Boron presence in CHTC samples reduced number of surface active sites for oxygen adsorption and consequently improved their electrochemical response as electrode material for carbon paste electrode

Thermal treatment influence on the surface characteristics of the borondoped hydrothermal carbon

Structural and surface characterization of pristine and boron doped carbonized hydrothermal carbons (CHTC) is reported. Boron was introduced into glucose precursor solution with concentration of 0.2% and 1%. Following hydrothermal treatment, samples were carbonized to 1000oC and examined by Raman spectroscopy and temperature programmed desorption. Characterization of obtained samples as material for carbon paste electrode was performed by cyclic voltammetry measurements of the Fe (CN)6 3-/4- redox couple. Structural analysis showed that lower boron content in precursor solution induced structure ordering, while higher amount of boron caused structural disorder of CHTC sample. Boron presence in CHTC samples reduced number of surface active sites for oxygen adsorption and consequently improved their electrochemical response as electrode material for carbon paste electrode

Carbon cryogel as an adsorbent for removal of Cd(II), Zn(II) and Ni(II) ions from water

Zagađenje vodenih tokova teškim metalima je jedan od najakutnijih ekoloških problema današnjice. S obzirom na to da teški metali nisu biorazgradivi, oni se akumuliraju u životnoj sredini i na taj način ulaze u lanac ishrane ljudi i životinja, pa kao veoma toksične materije, mogu izazivati niz opasnih i često neizlečivih bolesti. Iz tog razloga, istraživači godinama u nazad razvijaju nove i usavršavaju postojeće tehnike za prečišćavanje otpadnih voda od ovih zagađujućih materija [1]. Za prečišćavanje vode zagađene teškim metalima mogu se koristiti različite metode: hemijska precipitacija, elektrohemijski tretmani, filtracija, reverzna osmoza, jonska izmena, membranski procesi, adsorpcija. Jedna od najčešće korišćenih je adsorpcija, koja zbog mogućnosti regenerisanja adsorbenta, odgovarajućim desorpcionim procesom, predstavlja veoma efektivnu i ekonomičnu metodu. Zahvaljujući razvijenoj specifičnoj površini i poroznosti, kao i prisustvu funkcionalnih grupa na površini, različiti ugljenični materijali pokazuju visoku efikasnost u uklanjanju teških metala iz vode. Karbon kriogel (CC) predstavlja ugljenični materijal razvijene mezoporoznosti čije se adsorpcione karakteristike mogu poboljšati optimizacijom i kontrolisanjem parametara dobijanja. U ovom radu je ispitana mogućnost uklanjanja jona teških metala (Cd2+, Ni2+ i Zn2+) iz vode, korišćenjem karbon kriogela i hemijski modifikovanog karbon kriogela. Prvi korak u sintezi karbon kriogela je polikondenzacija rezorcinola i formaldehida, u prisustvu natrijum-karbonata kao katalizatora. Organski kriogel pripremljen je solgel tehnologijom uz naknadno sušenje postupkom zamrzavanja, dok je karbonizacija organskog kriogela vršena u inertnoj atmosferi argona na temperaturi od 800 o C [2]. U cilju poboljšanja adsorpcionih karakteristika karbon kriogela, izvršeno je hemijsko modifikovanje korišćenjem 5 M HNO3 . Karakterizacija materijala izvršena je merenjem specifične površine BET metodom, određivanjem tačke nultog naelektrisanja metodom masene titracije, kao i određivanjem vrsta funkcionalnih grupa prisutnih na površini materijala, metodom infracrvene spektroskopije sa Furijeovom transformacijom (FTIR). Ispitan je uticaj pH vrednosti rastvora, početne koncentracije jona metala u rastvoru, kao i vremena kontakta na adsorpciju teških metala uzorcima karbon kriogela.Primenjenom hemijskom modifikacijom karbon kriogela ne dolazi do bitnijih promena u specifičnoj površini i poroznosti materijala. S druge strane, ovim postupkom dolazi do izmene površinske hemije materijala, uvođenjem novih, i povećanjem broja postojećih kiselih površinskih grupa, što je pokazano FTIR analizom i smanjenjem vrednosti tačke nultog naelektrisanja sa pHPZC = 9,3 na pHPZC = 3,1. Adsorpcija jona teških metala na modifikovanom i nemodifikovanom karbon kriogelu vršena je na pH = 6, jer pri ovoj pH vrednosti materijali pokazuju najveći adsorpcioni kapacitet, a ujedno je izborom ove pH izbegnuta precipitacija hidroksida metala. Izmene u hemiji površine dovode i do izmena adsorpcionih karakteristika karbon kriogela. Kako površinske grupe predstavljaju aktivna mesta za adsorpciju jona teških metala, povećanje količine površinskih grupa kod modifikovanog karbon kriogela dovodi do višestrukog povećanja adsorpcionog kapaciteta

Voltammetric determination of linuron insecticide in methanol using a boron doped, glassy carbon and commercial glassy carbon electrode

This paper presents voltametric studies of the linuron insecticide (3-(3,4-dichlorophenyl)-1methoxy-1-methylureum) on a boron doped glassy carbon (GCB), glassy carbon (GC) prepared in our laboratory and commercial glassy carbon electrode. The method, operated in the differential pulse voltammetric mode, works in the concetracion range from 0.62 to 26.09 mg L-1. We determined a peak potential, Ep, (1.25V), linear range and LOD for linuron in the sulfuric acid as a supporting electrolyte (pH=0.7) for all applied electrodes. GCB shows the broadest linear range and sensitivity. This appears to be the first aplication of a boron doped glassy carbon electrode to the voltammetric determination of linuron insecticide

Mathematical modeling of pesticide adsorption on activated hemp fibers

Activated carbon obtained by carbonization and activation of waste hemp fibers was used as an efficient, low-cost sorbent for pesticide removal. Data obtained from batch and continuous process of pesticide adsorption was used for development of the mathematical model that describes the phenomenon of pesticide transport through the porous sorbent matrices. Effective diffusion coefficient and the pesticide concentration profile within the activated hemp fibers, obtained as results of proposed model, give the insight in the mechanism and the rate of adsorption process and pesticide transport through the sorbent. A good agreement between model prediction and the experimental data indicates that the proposed mathematical model can be successfully used for optimization and selection of appropriate adsorption process for pesticide removal