Površinska svojstva i otapanje koloidnih čestica SiO2

master's thesis

• Title (english): Surface properties and dissolution of SiO2 colloid particles
• Author: Dragutin Hasenay
• Mentor: Tajana Begović (mentor)
• Committee member: Tajana Begović (predsjednik povjerenstva)
• Committee member: Ivan Nemet (član povjerenstva)
• Committee member: Đani Škalamera (član povjerenstva)
• Committee member: Josip Požar (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Chemistry); Zagreb
• Defense date and country: 2023-02-24, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry

Abstract

Mjerena su površinska svojstva i otapanje čestica amorfne silike veličine 200 nm. Metodom potenciometrijske masene titracije određen je interval u kojem se nalazi točka nul-naboja. Metodom elektroforeze određena je izoelektrična točka čestica silike u vodenoj otopini pri dvije ionske jakosti u prisutnosti i odsutnosti otopljene silikatne kiseline. Proces otapanja koloidnih čestica silike u vodenim otopinama različite pH vrijednosti praćen je metodama dinamičkog i statičkog raspršenja svjetlosti te spektrometrijom masa uz induktivno spregnutu plazmu. Silika se otapa otpuštanjem SiO(OH)+ i OH– iona s površine pri čemu nastaju nabijene praznine koje mijenjaju površinski naboj. Površinski naboj određuje brzinu otapanja silike. Nastanak pozitivno nabijenih praznina ubrzava otpuštanje SiO(OH)+, a nastajanje negativno nabijenih praznina ubrzava otpuštanje OH– iona. Brzina otapanja amorfne silike povećava se od rc ≈ 10– 16 mol s–1cm–2(pri pH = 3) do rc ≈ 10–14 mol s–1cm–2(pri pH = 11). Vrijednosti brzine otapanja
uspoređene su s empirijskom jednadžbom za otapanje amorfne silike prethodno predloženoj u literaturi.

Abstract (english)

Surface properties and dissolution of 200 nm amorphous silica particles were measured. The interval of point of zero charge of silica particles in aqeous solutions was determined by means of potentiometric mass titration. The isoelectric point was determined electrophoreticaly at two ionic strenghts, and in the presence and the absence of dissolved silicic acid. Dissolution process of silica particles in aqueous solutions with different pH values was monitored by means of dynamic and static light scattering, and inductively coupled plasma - mass spectrometry. Silica dissolution occurs via removal of SiO(OH)+, and OH– from the silica surface. Surface charge regulates the rate of silica dissolution. Creation of positively charged vacancies accelerates the removal of SiO(OH)+, while creation of negatively charged vacancies accelerates the removal of OH– ions. The rate of dissolution i.e. the rate of cation removal from silica surface, increases from rc ≈ 10–16 mol s–1cm–2 (at pH = 3) to rc ≈ 10–14 mol s–1cm–2(at pH = 11). The values of dissolution rate were compared with previously proposed empirical equation for amorphous silica dissolution.

• Keywords: električni međupovršinski sloj; koloidni sustav; otapanje; raspršenje svjetlosti; silika
• Keywords (english): colloid system; dissolution; electrical interfacial layer; light scattering; silica
• Language: croatian
• URN:NBN: urn:nbn:hr:217:118971
• Project: Number: IP-2020-02-9571; Title: Fizikalna kemija procesa na međupovršini mineral/otopina (poli)elektrolita; Title: Physical chemistry of processes at mineral/(poly)electrolyte solution interface; Acronym: POLYMIN2; Leader: Tajana Begović; Jurisdiction: Croatia; Funder: HRZZ; Funding stream: IP
• Study programme: Title: Graduate university studies in chemistry; specializations in: Research programme; Course: Research programme; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra kemije (magistar/magistra kemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Embargoed access; Embargo expiration date: 2024-08-24
• Created on: 2023-03-21 13:52:04