Editing Litter box (section)

===Silica gel litter===
[[File:Kattengrit-2.jpg|thumb|right|Silica "crystal" litter]]
[[Silica gel]] litter, often referred to as "crystal litter", is a porous granular form of [[silicon dioxide]], has the highest absorbency of any litter, and has excellent moisture control and complete odor elimination for an extended period of time compared to other litters. It is typically prepared through a sol-gel process, which involves the hydrolysis and condensation of silica precursors such as tetraethylorthosilicate (TEOS) or sodium silicate (Na2SiO3).<ref>{{Cite journal |last=Demirdöğen |first=R. E. |title=Chemical Synthesis Method for Production of Silica Gel as a Sorbent Material |s2cid=208628750 }}</ref> The porous structure of silica gel enables it to trap moisture within its network of interconnected pores, effectively locking away urine and preventing it from spreading or leaking. Moreover, many silica gel litter formulations incorporate activated carbon or other odor-neutralizing compounds, which further enhance the litter's ability to control unpleasant smells.<ref>{{Cite journal |last1=Zhuang |first1=Guo-Liang |last2=Tseng |first2=Hui-Hsin |last3=Wey |first3=Ming-Yen |date=October 2014 |title=Preparation of PPO-silica mixed matrix membranes by in-situ sol–gel method for H2/CO2 separation |url=http://dx.doi.org/10.1016/j.ijhydene.2014.08.050 |journal=International Journal of Hydrogen Energy |volume=39 |issue=30 |pages=17178–17190 |doi=10.1016/j.ijhydene.2014.08.050 |issn=0360-3199|url-access=subscription }}</ref> In addition to its physical structure, the chemical composition of silica gel also contributes to its performance as a cat litter. The surface of silica gel is covered with silanol (Si-OH) and siloxane (Si-O-Si) functional groups.<ref>{{Cite journal |last1=Meti |first1=Puttavva |last2=Wang |first2=Qi |last3=Mahadik |first3=D. B. |last4=Lee |first4=Kyu-Yeon |last5=Gong |first5=Young-Dae |last6=Park |first6=Hyung-Ho |date=January 2023 |title=Evolutionary Progress of Silica Aerogels and Their Classification Based on Composition: An Overview |journal=Nanomaterials |language=en |volume=13 |issue=9 |pages=1498 |doi=10.3390/nano13091498 |doi-access=free |pmid=37177045 |pmc=10180228 |issn=2079-4991}}</ref> These groups interact with water molecules through hydrogen bonding and dipole-dipole interactions, enabling the material to absorb and retain moisture effectively.<ref>{{Cite journal |doi=10.1016/j.apsusc.2023.158616 |s2cid=263687166 |title=Dominant factors for moisture resistance of sol–gel silica coatings: Surface chemical composition or inner microstructure? |date=2024 |last1=Zhang |first1=Chen |last2=Wang |first2=Hongqiang |last3=Shen |first3=Jun |last4=Wang |first4=Xiaodong |journal=Applied Surface Science |volume=642 |bibcode=2024ApSS..64258616Z }}</ref>

Some owners praise its absorbency because {{convert|4|-|5|lb|kg}} can absorb liquid and odor for up to 30 days for one healthy normal weight cat.{{citation needed|date=December 2018}} It is important to lightly stir the crystals daily while scooping the solid waste, otherwise urine can pool in the box. When crystal litter is saturated, at the end of 30 days or so, it begins to smell and is visibly saturated (the white crystals have turned slightly yellow). In comparison, over the same time period it may take {{convert|20|–|30|lb|kg|abbr=on}}{{Citation needed|date=August 2019}}<ref>{{cite web |url= http://pets.thenest.com/liquid-absorbing-properties-cat-litter-9654.html |title=Liquid Absorbing Properties of Cat Litter |last=Anne |first=Melodie |website=Pets.TheNest.com |access-date=2 August 2019}}</ref> or more of clay or clumping litter, because it is necessary to replenish the litter that is removed when the clumped urine is scooped out. No replenishing is necessary with silica gel (crystal) litter.