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CHEM 375 > Midterm 2 > Flashcards

Midterm 2 Flashcards

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1
Q

What are colloidal particles?

A

small perticles that are often on the order of wavelength of light - causes scattering
- colloidal facilitated transport - small particles normally absorbed by sediments but instead transported through hydrosphere

  • clay is also one of these
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2
Q

Important feature of colloids

A
  • ability to adsorb molecules or ions from the surrounding solution
  • may be reversible
  • may bring about decreased concentrations of solutes in water or may facilitate movement instead
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3
Q

What metals would be found in high pE environments that can be oxidized to form colloidals

A

Fe2O3xH2O and MnO2xH2O

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4
Q

What form would metals be found in in a low pE environment - anoxic conditions

A

found in deep water sediments
- insoluble Fe and Mn oxides are reduced
- can find colloidal FeS and MnS in anoxic sediments

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5
Q

What colloids are formed in low pH environments?

A
  • waters containing DOM encounter acid env
  • acid insoluble humic acid forms
  • organic colloids can be produced in marine organisms
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6
Q

What colloids are found in a high pH environment?

A
  • CaCO3
  • biomass synthesis raises pH during the day
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7
Q

Can colloidal MnO2 have negative and positive surface charges?

A

yes can have OH+ and OH-
- means they can bind cations or anions depending on pH

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8
Q

How would adsorption of metal cations work on MnO2?

A

Metal can coordinate with OH – O groups
- will result in a change in protons - may change pH

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9
Q

How does adsorption of anions on MnO2 work?

A

trickier than cataions
- anion like a phosphate will fully diplace OH- instead of just H and two O from PO4 will bindq

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10
Q

What is coagulation?

A

the reduction of electrostatic repulsion such as colloidal particles of identical materials may aggregate

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11
Q

What is flocculation?

A

uses bridging compounds which form chemically bonded links between colloidal particles and enmesh the particles in relatively large masses called floc networks

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12
Q

What is double layer compression?

A

Hydrophobic colloids that are stabilized by electrostatic repulsion may be coagulated by the addition of small quantities of salts that contribute ions to the solution, reducing the electrostatic repulsion between particles.

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13
Q

What flocculants should be used when?

A

use opposite charge flocculant to colloidal

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14
Q

What will happen to pollutant compound when encountering colloidal humic substances in the soil?

A

will bind and complex reducing toxicity

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15
Q

How was adsorption of HA and FA on SiO2 affected by different size particles and pH/ ionic strength

A

much stronger adsorption on smaller particles - same mass but can create much larger surface area

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16
Q

What is humic acid?

A

material that precipitates from the acidified extract ( less oluble) and contain more arimatic groups

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17
Q

What is fulvic acid?

A

an organic material that remains in the acidified solution , richer in carboxylic acids, more alipathic groups thn humic acid

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18
Q

Humic acids

A

material that precipitates from the acidified extract less soluble and contain more aromatic groups vs aliphatic groups, higher mol weight, more ionizable groups

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19
Q

Fulvic acids

A

organic material that remains in the acidificied solution (more soluble), richer in carbacids, phenol and ketone groups, more alipathic groups than humic acids, lower mol weight, low sol, less ionizable groups but still polar

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20
Q

Which species are more strongly bound in the SiO2 expt, fulvic or humic acids

A

Humic acids by about double the strength

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21
Q

What are the surface charges above and below teh IEP / PHo

A

When pH is below IEP / pHo the surface charge is positive
when pH is above IEP / pHo, then the surface charge is negative

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22
Q

How does ionic strength impact the surface charge in different pH

A

basically makes less extremes, higher ionic strength will have a slightly lower surface charge than less ionic strength

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23
Q

What are the three kinds of water

A
  • purification for domestic use / drinking water
  • treatment for specialized industrial fabrication - microchips
  • treatment of wastewater to make it acceptable for release or reuse - ne
    ed to get rid of contaminants / microbes etc
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24
Q

What needs to be removed from water

A
  • volatiles H2S CH4
  • solids / colloids
    -excess water hardness
  • excess iron and manganese
  • Dissolved organics
  • pathogens
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25
3 categories of water treatment
- drinking water - high standards see notes - industrial use - release of water back to the environment
26
What impacts water quality guidelines
- physical properties - general chemical properties - pH, salinity, hardness - specific elements - radiological properties - microbial properties
27
Why might pH affect the bioavialbility of pesticides / fungicides
acidic pH could protonate groups increasing charge and therefore solubility - and making them incrase risk to human health - on the other hand can protonate ionic groups (ie kick out sodium) and change the molecule from being soluble to being volatile and increase risk of inhaling through lungs
28
where do you find arsenic
same place you find uranium, so sask
29
Steps in municipal water treatment
primary settling aeration removal of excess hardness coagulation flocculation
30
Aeration in water treatment
-remove volatile substances - removal of easily oxidizeable substances - aerate chemically rather than physically - Fe can be removed by precipitation to ferric iron - colloidal suspsentions are harder to remove - homeowners can
31
removal of hardness in water treatment
Lime/soda processes - Use of NaCO3 to drive up pH to convert more HCO3- to CO32- which can then bid with Ca and precipitate out
32
What is the dual function of aluminum?
Can function as a coagulant and a flocculant - bridged between multiple Al(OH) groups by OH- - undergoes charge neutralization as it picks up OH- and will begin to form a flocc / coagulate
33
How does disinfection work for water treatment?
- water is made drinkable by killing pathogens - one of the last steps in treatment - chlorine, chlorine dioxide, ozone, UV radiation (non chemical process) - need some sort of residual activity in water to prevent recontamination
34
What does chlorine do in water
- reduces alkalinity - kills microbes - Cl2 + H2O ----- H+ + Cl- + HOCl
35
Why is HOCl 100x better at killing bacteria than OCl-
HOCl is neutral and can approach the negatively charged bacteria better than OCl-
36
How does UV radiation act as a disinfectant?
Radiation less than 300nm damages organisms - Damages DNA meaning cells cannot replicate properly Advantages - easy setup and low cost - economical - short contact time - no residue - not influenced by pH and temp Disadvantages - need to remove UV absorbing groups - no residual activity - thickness of water film matters
37
What happened in Bangladesh?
Particles of iron oxide bound to arsenic made it way into aquifers, poisoned millions
38
Important organically bound metals and metalloid pollutants in water?
Alklyated metals (Pb) Methylated metals (Hg) tetraethyllead used to be in gasoline methylated mercury from anoxic bacteria mobilized insoluble forms organotin compoinds used as biocides tributyltin chloride in biocides
39
Inorganic pollutants in water
Cyanide - toxic, from metal cleaning/ coke ovens - pollutes fish downstream from mineral processing plants Ammonia - at high pH - added to drinking water for disinfection but toxic in high amounts Free CO2 - in water from decay of organic matter - makes water corrosive due to lowering pH H2S - industrial sources - toxic, precipitates heavy metals NO2- - toxic but rare SO2- added to water as O2 scavenger ClO4- -industrial pollutant but might be used in disinfection Asbestos - cancer
40
Algal nutrient pollution in water?
eutrophication when too many nutrients are in water - uncontrolled growth of algae followed byy decay - depletes O2 often limited by P
41
Effects of acids, alkalinity, salinity on water
Acid - often in acid mine water H2SO4 / strong acids - industrial source of pollution Alkalinity - NaHCO3 - natural and geological sources - worsened by irrigation Salinity - salts such as NaCl and Na2SO4 - increased in municipal water systems - increased by irrigation - major problem in heavilly irrigated areas
42
Oxygen and oxidants in water
dissolved oxygen is important - depleted by oxidation of NH4, Fe2+, SO32- and mainly degredation of biomass CH2O + O2 --- CO2 + H2O biochemical oxygen demand refers to the amount of oxygen consumed in a volume of water by the biodegradable organic matter in it
43
Organic pollutants in water
sewage - contains many pollutants and pathogens - most significant is biomass as BOD
44
What are soaps
salts of long chain fatty acids - form micelles which can enclose water insoluble particles like grease and oil - lowers water surface tension to clean - biodegradable - produce insoluble salts with divalent metal ions, mainly calcium, whihc removes them from water, but may reduce cleaning power in hard water
45
What are detergents
synthetic detergents lower water surface tension - do not form precipitates with hardness ions - amphiphillic structure with ionic head and hydrocarbon tail - poorly biodegradable - sulfonate head (instead of COO-)
46
Why are pesticides a concern for water pollution?
- highly biodegrataion resistant - carcinogens - adverse reproductive or developmental effects - neurotoxins such as cholinesterase inhibitors - acutely toxic - groundwater contaminants
47
What are organophosphate insecticides?
though biodegradable and not generally environmentally harmful, some toxic effects occur (acetylcholinesterase inhibitors)
48
What are the two major bipyridilium herbicides?
diquat and paraquat
49
How does chlorine disinfection not pose a risk?
Chlorine species will form trihalomethanes when reacted with organics - can remove organics prior to chlorination but its expensive - chlorinated organic compounds can be toxic but generally the hazards of not disinfecting are greater than possible hazards of disinfection
50
What is chlorine demand, breakpoint chlorine and free chlorine?
Chlorine demand is the amount of chlorine that is required to satisfy all impurities breakpoint chlorine - point where chlorine demand is satisfied free chlorine - additional chlorine past the breakpoint as HOCl and ClO-
51
How can ammonium be used to increase residual chlorine / remove ammonia/ how does Cl2/HOCl disinfection work
NH4 can bind with HOCl --- NH2Cl + H2O - chloramines are weaker disinfectants but last longer - can cause a problem if theres too much ammonia - need to balance Cl:N - reaction of ammonium ion with hypochlorite can form NH2CL which can react again to seperate into N2 gas and Cl-
52
How does chlorine dioxide work as a disinfectant?
must be generated on site - reactive with organics and light NaClO2 + H2SO4 --- 8ClO2 - reaction gives ClO2 more effective than HOCl bubt more expensive - disinfects through oxidation ClO2 + C6H5OH --- ClO2- + oxidized biomass - no residual activity can possibly create toxic ClO3- - does not produce trihalomethanes
53
How does ozone disinfection work?
partitioned into water, mroe soluble than O2 and CO2 (due to dipole moment) Ozone is used as an oxidant 2O3--- 3O2 - generated by electrical discharge - expensive unless large scale - decomposes rapidly, still need residual chlorine - corrosive to pipes and must be aerated
54
How does UV radiation disinfection work?
- radiation less than 300nm damages organisms - damages DNA, cells cant replicate - easy to set up / low cost -short contact time - no toxic residues - not affected by temp or pH - need to remove any UV absorbing materials first - no residual activity - requires a thin column of water
55
What happened in Grassy narrows?
mercury poisoning due to industrial pollution in the 60s and 70s - indigenous communities
56
What can aluminum in the water cause?
- anemia, softening of bones, demntia / alzheimers present in natural waters due to using alum filters asprin - can form gel(???)
57
What can sodium in the water cause?
present in softened water - gross after 300ppm - can lead to hypertension - dont drink softened water - used in industry and as deicers which gets into groundwater
58
What organotin compounds are in the water and what do they cause?
fungicides, disinfectants - tetrabutyl tin chloride and tributyl tin used in ships - High volume leads to pollution / endocrine disruption in aquatic organisms
59
Two main sources of sewage?
aqueous municipal waste - industry / ag waste
60
3 steps to sewage treatment?
primary settling secondary treatment tertiary treatment
61
Primary settling in sewage treatment?
removal of solids - done by filtration and settling - water is slowed and settled, saskatoon has screens - solids go to landfills - effluent has high BOD
62
What is secondary treatment in sewage treatment?
removes BOD by 90% - removes sludge and scum - done by trickling flter or activated sludge reactor trickling filter - large tank with gravel and sand that supports microorganisms that degrade BOD - can be poisoned by some wastes/ doesnt work well in cold activated sludge - done in an enclosed tank, microorganisms are recycled- solids collected in a settling tank
63
What is sewage sludge and what dp we do with it?
- water content is high - water removed by air dryinh In saskatoon methane producing bacteria are used to degrade sludge (removes all O2) and methan will fuel boilers in treatment plants - disposed in landfills, incineration, ocean dumping (all bad) land spreading ( better if used as fertilizer) - may contain resistant organochlorine comppounds - may contain heavy metals from industry - must increase pH if spreading in an area to be planted to keep metal bioavailability low) 9 sludge will bind to metals making them less available in soils
64
What is tertiary treatment of sewage?
removal of final specific compopunds - removal of phosphorus is most common (as P can lead to eutrophication) - precipitate P with lime at high pH - can use Al or Fe at lower pH - bioreactors can remove some P but innefective
65
What is green water?
desalinating sea water or brackish groundwater - used in coastal cities where grounwater is saline - requires reverse osmosis and high energy (nuclear) - big on recyling and reusing water wastewater treatment effluent is ran through wetlands which purifies naturally with plants and bacteria / soil - water moves and can be used to recharge groundwater, irrigation, non potale uses - filters can remove organics from wetland / do reverse osmosis again to make potable water for cities
66
How to remove organics in water?
- oxidation by secondary treatment - adsorption on activate carbon filters - reverse osmosis - also desalinates water but expensive
67

CHEM 375 (4 decks)

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