Chapter Four · failure evidence
What Solvent Extraction & Crystallization got wrong, from 46 dissertations
The records describe various failures and trade-offs encountered in solvent extraction and crystallization processes across synthetic, analytical, and separation procedures. Authors frequently reported difficulties including inadequate solute solubility, co-precipitation of interfering matrix components, unintended phase and polymorph formation, continuous crystallizer clogging, and ineffective chiral separation mechanisms. These records come from PhD theses at 21 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Solvent selection fails due to dissolution limits, poor phase separation, or impractical volatility
Attempts to dissolve solutes or induce crystallization frequently failed when compounds exhibited extreme insolubility, high lattice energy, or excessive hydrophobicity in chosen solvents. Other solvent selections proved impractical because solvents were too volatile, required excessive evaporation times, or failed to induce necessary liquid-liquid phase equilibrium.
Tried and failed
dielectric constant-based solvent selection for phase separation applied to salt-induced liquid-liquid extraction mixtures. Outcome: no signal. Reason: low dielectric constant solvent failed to induce liquid-liquid phase equilibrium, disproving pure dielectric-based precipitation theories
Critical Material Recovery from Salt-Lakes and Spent Batteries with Membranes and Solvents · MIT
Tried and failed
high-concentration transition metal salt dissolution in ionic liquids applied to metal-containing ionic liquid stationary phases. Reason: exceeded solubility limit at room temperature, failing to form a homogeneous solution
Inverse gas chromatography for crucial separations using ionic liquids · UT Austin
Considered and rejected
Considered and rejected: Rejected solvent-based precipitation due to poor solubility requiring large, impractical amounts of organic solvents.
Considered and rejected
Considered and rejected: Rejected DMSO and DMF for solution crystallization despite high theobromine solubility due to excessive solvent evaporation times.
Kokryształy alkaloidów purynowych – teobrominy, teofiliny oraz kofeiny Cocrystals of purine alkaloids – theobromine, theophylline and caffeine · AMUR - Repozytorium Uniwersytetu im. Adama Mickiewicza w Poz
Considered and rejected
Considered and rejected: Classical solution crystallization for F6PEN and PFT: rejected due to extremely low solubility, replaced by vacuum-based and ionic-liquid-mediated OMBD growth.
Untersuchung der strukturellen und optoelektronischen Eigenschaften fluorierter organischer Halbleiter Investigation of the Structural and Optoelectronic Properties of Fluorinated Organic Semiconductors · open_UMR Marburg DSpace 10.0
Considered and rejected
Considered and rejected: Precipitation workup with light petroleum for thermal cyclization intermediates [16-19] was replaced with celite adsorption and flash column chromatography because intermediates [16-19] were soluble in diphenyl ether reaction media.
Synthesis of novel scaffolds as selective ligands for the alpha-beta interface of the GABA-A receptor Synthese neuer Strukturen als selektive Liganden für das alpha-beta Interface des GABA-A Rezeptor · DSpace-CRIS at TU Wien
Considered and rejected
Considered and rejected: Direct recrystallization of [PtCo(SAc)4(4,4'-bipy)]inf from reaction powder was rejected due to minimal solubility; instead, crystals were grown directly from the reaction mixture using liquid-liquid layering of PC and toluene.
Chemical design of single molecule electronic components and quasi-1D chains · OpenBU
Tried and failed
solution-phase purification and characterization applied to highly hydrophobic oligopeptoids. Reason: extreme hydrophobicity prevented dissolution required for liquid-phase purification and characterization
PRECISION ENGINEERING OF SMALL MOLECULES AND OLIGOMERS FOR ADVANCED TECHNOLOGIES · Cornell
Tried and failed
selective solvent dissolution of uncrosslinked polymer applied to polystyrene thin film removal. Outcome: worse than baseline. Reason: aliphatic and polar solvents yielded incomplete polymer dissolution compared to aromatic solvents like toluene
Considered and rejected
Considered and rejected: Rejected using diethyl ether for dissolution/purification of bis(diphenylphosphino)benzene diamine ligands due to sparse solubility; used acetonitrile recrystallization instead.
Catalysis and Coordination-Driven Self-Assembly: Exploring Reactivity of Multinuclear Architectures · DSpace at SUNY Buffalo
Considered and rejected
Considered and rejected: Rejected using non-ethanol solvent mixtures (acetone, diethyl ether) for SPC recrystallization because they remained solutions or formed uncontrolled aggregates.
ENGINEERED FORMULATIONS FOR SUSTAINED OCULAR DRUG DELIVERY · JScholarship
Tried and failed
hydrocarbon solvating agent dissolution of ionic solid applied to alkali metal amide complexes. Reason: high crystal lattice energy prevented dissolution in weakly coordinating olefinic solvents
STRUCTURE-REACTIVITY PRINCIPLES OF SODIUM HEXAMETHYLDISILAZIDE · Cornell
Precipitation and extraction workups suffer from impurity co-isolation, matrix interference, and product loss
Solvent precipitation and extraction techniques frequently co-precipitated unwanted salts, lipids, or radionuclides that interfered with downstream analysis and bioassays. In addition, target analytes suffered severe recovery losses when products remained trapped within polymeric byproducts or non-compact sludges.
Tried and failed
isopropanol acetonitrile protein precipitation extraction applied to lysophospholipid quantification in biological samples. Reason: low unnormalized extraction recovery percentage below fifty percent
Considered and rejected
Considered and rejected: Rejected salting-out extraction using 0.5 M NaCl due to salt crystallization and ion suppression matrix effects in LC-MS.
Chemical exposures in drinking water: contaminant analysis and physicochemical behavior · MIT
Considered and rejected
Considered and rejected: Rejected using solvent precipitation (SolvPrec) for broad HBM screening despite high chemical recovery, because it co-extracts salts and lipids that interfere with bioassays and mass spectrometry.
Effect-based human biomonitoring of complex chemical mixtures using high-throughput target screening and in vitro bioassays · Publikationssystem UB Tuebingen
Considered and rejected
Considered and rejected: Rejected Dextran (450k-650k) as a phase-separation additive due to low solubility and precipitation during extraction, causing poor repeatability.
Introduction of a new two-phase extraction method covering a broad spectrum of analytes in food and environmental samples and its miniaturization to determine the pesticide body burden of individual invertebrates · Publikationssystem UB Tuebingen
Tried and failed
precipitation separation applied to radiosilver isolation from cesium interference. Reason: interfering cesium radionuclides could not be completely eliminated by precipitation alone
Environmental impact of noble metal radionuclides and their use in nuclear forensics Umwelteinwirkung von Edelmetallradionukliden und deren Verwendung in der nuklearen Forensik · Leibniz Universität Hannover Repository
Tried and failed
single-stage washing during precipitation extraction applied to biopolymer isolation from biomass. Outcome: worse than baseline. Reason: incomplete removal of extraction reagents caused poor physical and structural properties in the final product
In-Situ Resource Utilization of Pectin and Bosch Carbon for Energy Storage · Texas Tech
Tried and failed
solid phase extraction of organic stock solutions applied to polycyclic aromatic hydrocarbon quantification. Reason: improperly prepared stock solution caused sample precipitation and impossible extraction recoveries
Tried and failed
chloroform-methanol precipitation applied to proteomic sample preparation with non-ionic detergents. Outcome: worse than baseline. Reason: interfacial pellet loss and inefficient detergent removal compared to bead-based clean-up
Lost to a baseline
Recrystallization of 2-amino-5-chlorobenzophenone yielded only 40–55% due to product trapping in polymeric PMHS byproducts, underperforming column chromatography (79–84%).
Stereoselective and Economical Methods for Chemical Synthesis of Essential Medicines · MIT
Considered and rejected
Considered and rejected: Rejected fractional crystallization for the separation of mono-, di-, and tributyl derivatives of 3,5-thiomorpholinedione because attempts to isolate the respective products were unsuccessful; used preparative gas chromatography instead.
The formation and chemistry of certain heterocyclic dianions · Virginia Tech
Crystallization yields competing phases, unwanted polymorphs, or degraded products
Variations in precursor solubility, moisture contamination, and reaction stoichiometry caused crystallizations to precipitate unintended mineral phases or non-stoichiometric compositions. Other procedures resulted in polymorph mixtures, arrested amorphous glasses, or unwanted isomerization of target metal complexes.
Tried and failed
stoichiometric solution recrystallization for mixed-composition crystals applied to mixed-halide layered perovskite synthesis. Reason: differential precursor solubilities in the solvent led to non-stoichiometric incorporation of halides
Tried and failed
sub-stoichiometric reagent dosing in reactive crystallization applied to selective precipitation of target crystalline mineral. Reason: insufficient reactant ratio favoured competing mineral precipitation over the desired target crystal
Assessing the potential of full-scale phosphorus recovery by struvite precipitation · Cranfield
Tried and failed
thermodynamic oversaturation modeling to induce metastable precipitation applied to iron sulfide mineral synthesis pathway simulation. Reason: the thermodynamically stable phase precipitated at lower threshold concentrations than the targeted metastable phases
Tried and failed
aqueous acid solution cooling-induced crystallization applied to hybrid metal halide perovskite synthesis. Reason: poor solubility of alkali precursor in concentrated acid caused premature precipitation and phase separation
Syntheses and Photophysical Studies of Two-Dimensional Hybrid Organic-Inorganic Semiconductors · MIT
Tried and failed
solution crystal growth using non-anhydrous solvents applied to moisture-sensitive halide perovskite single crystals. Outcome: unstable. Reason: residual water caused immediate precursor degradation and impurity phase precipitation
Investigation of Lead-free perovskites for Optoelectronic Application · EPFL
Tried and failed
sequential precipitation with reversed stage order applied to electrochemical mineral separation from brine. Outcome: worse than baseline. Reason: residual carbonic acid from initial carbonation consumed electrogenerated hydroxide, preventing subsequent alkaline hydroxide precipitation
Tried and failed
liquid-liquid demixing for crystallization applied to ternary polymer-solvent-antisolvent mixtures. Reason: polymer-rich phases kinetically arrested into amorphous glasses instead of nucleating crystalline phases
Lost to a baseline
ROY crystallization on U-CNC, O-CNC, and J-CNC drop-cast films showed poorer polymorph selectivity than aerogel confinement, yielding mixtures of polymorphs (Y, ON, and R) due to interference from unattached bulk crystallization.
Surface-Modified Cellulose Nanocrystal Gels for Applications in Pharmaceutical Crystallization · Georgia Tech
Considered and rejected
Considered and rejected: Rejected recrystallizing crude cis-[Pt(am)2Cl2] complexes because recrystallization promoted isomerization to the thermodynamically favored trans isomer.
New Complexes of Titanium (IV) and Platinum (II) · TXST Digital Repository
Considered and rejected
Considered and rejected: Rejected direct crystallization without prior purification because co-present xylo-aminooxazoline (XAO) acts as a crystal habit modifier, causing racemic rosette twinning
A New Spin on the Origin of Biological Homochirality · Harvard
Continuous and membrane crystallization systems experience clogging, aggregation, and mass transfer limits
High supersaturation and rapid primary nucleation frequently caused severe crystal agglomeration, column flooding, and transfer line clogging in continuous and packed configurations. Similarly, membrane contactors and single-fibre crystallizers suffered from volatile reactant slip and limited reaction boundary layers compared to batch systems.
Tried and failed
driving homogeneous nucleation via supersaturation rate control applied to solution crystallization. Reason: high primary nucleation rates caused particle collisions leading to crystal aggregation and cementation
Strategies for controlling nucleation and crystal growth in membrane distillation crystallisation. · Cranfield
Lost to a baseline
Continuous enzymatic reactive crystallization had lower initial reaction mass efficiency (0.343 kg/kg) compared to batch enzymatic reactive crystallization (0.368 kg/kg) prior to incorporating substrate recovery
Continuous enzymatic reactive crystallization of beta-lactam antibiotics · Georgia Tech
Tried and failed
reactive absorption with in-situ crystallization applied to packed absorption columns. Outcome: unstable. Reason: rapid nucleation and agglomeration caused column flooding at low supersaturation levels
SCALE up of hollow fibre membrane contactors for biogas upgrading. · Cranfield
Tried and failed
membrane crystallization with reactive gas absorption applied to dilute reactant solutions. Reason: low initial reactant concentration prevented crystallization due to thermodynamic limits and kinetic pH drops
Chemically reactive membrane crystallisation reactor for CO₂ separation and ammonia recovery. · Cranfield
Tried and failed
membrane contactor reactive crystallization applied to volatile reactant recovery and crystallization. Reason: direct gas-liquid contact caused volatile reactant slip, leading to poor recovery into solid crystals
Chemically reactive membrane crystallisation reactor for CO₂ separation and ammonia recovery. · Cranfield
Tried and failed
short hydraulic retention time fluidized bed precipitation applied to nutrient recovery from wastewater. Outcome: worse than baseline. Reason: insufficient residence time and low reagent dosing limited precipitate formation and capture kinetics
Maximising struvite recovery from real wastewater sources · Cranfield
Tried and failed
chemical precipitation without solid support matrix applied to hydrolysed urine nutrient recovery. Reason: formed a fine, non-compact sludge that resisted solid-liquid separation by gravity or centrifugation
Towards circular sanitation systems: Resource recovery via pyrolysis of human excreta · Imperial
Lost to a baseline
Batch crystallization achieved higher nitrogen removal yield (up to 30%) than single-fibre membrane crystallization (up to 5%) due to whole-volume mixing versus thin boundary layer reaction
Chemically reactive membrane crystallisation reactor for CO₂ separation and ammonia recovery. · Cranfield
Considered and rejected
Considered and rejected: PFR configurations for reactive crystallization were rejected due to severe slurry settling, transfer line clogging, and difficult solid-solid separation compared to MSMPR crystallizers.
Development of an Improved Amino Ester Hydrolase for Continuous Reactive Crystallization Of Beta-Lactam Antibiotics · Georgia Tech
Left open by the authors
Problems the authors named and did not get to.
Left open
Perform life cycle assessment and techno-economic analysis comparing membrane distillation-crystallization lithium extraction against conventional methods. Blocker: None
AN INNOVATIVE MEMBRANE DISTILLATION-CRYSTALLIZATION PROCESS FOR BRINE TREATMENT · unevada
Left open
Identify and test solvents for the direct dissolution of lead sulfate or raw sulfurized lead paste without prior desulfurization. Blocker: Requires a wet chemistry laboratory, chemical reagents, and physical battery paste samples for dissolution testing
Natural deep eutectic solvents (NADESs) for lead acid battery recycling · Imperial
Left open
Pair SLiC-SPEs with conversion-type cathode materials in lithium batteries to evaluate reduction of active material dissolution loss. Blocker: Requires wet lab chemical synthesis and battery fabrication/testing apparatus.
Polyphosphazene- and Acrylate-Based Polymer Electrolytes for Lithium Batteries · Georgia Tech
Left open
Optimize crystallization below 0 °C directly from crude effluent to increase paracetamol yield above 50% and reduce recrystallization steps to one. Blocker: Requires a wet-lab chemical synthesis and crystallization setup with crude reaction effluent
Green, Renewable, and Continuous Manufacturing of the Active Pharmaceutical Ingredient Paracetamol · Georgia Tech
Left open
Develop and optimize a recrystallization procedure using an NH4F/MeOH quenching method to remove PMHS byproducts. Blocker: Requires a wet chemistry laboratory and physical reagents to perform reaction quenching and recrystallization experiments
Stereoselective and Economical Methods for Chemical Synthesis of Essential Medicines · MIT
Left open
Investigate methods to increase struvite crystal size from fine powder to granular form during precipitation. Blocker: Requires a physical wet lab with chemical reactors and wastewater liquors to run precipitation experiments
Assessing the potential of full-scale phosphorus recovery by struvite precipitation · Cranfield
Left open
Experimentally measure pressure-dependent stable Cr isotope fractionation during clinopyroxene and mineral-melt crystallization. Blocker: Requires a high-pressure experimental petrology laboratory and mass spectrometry facilities
The Stable Chromium Isotope Signatures of Earth's Silicate Reservoirs: Probing the Deep Earth through Time · Publikationssystem UB Tuebingen
Left open
Investigate wastewater pretreatment strategies using adsorption, coprecipitation, and solvent extraction to mitigate catalyst deactivation in aqueous phase reforming. Blocker: Requires access to wet chemical laboratories, real wastewater streams, and experimental reactor setups.
Valorisation of biomass-derived wastewaters via aqueous phase reforming for energy recovery: a multi-level performance assessment · IRIS - POLITO - prod
Left open
Model and optimize struvite crystallization kinetics and thermodynamics directly from real wastewater and hydrothermal liquefaction aqueous phase coproducts. Blocker: Requires real hydrothermal liquefaction aqueous phase samples, wet-lab experimental apparatus, and chemical characterization facilities
Left open
Test struvite precipitation effectiveness and product purity at lower operating pH without chemical pH correction. Blocker: Requires a wet-lab chemical reactor setup with wastewater centrifuge liquor samples.
Assessing the potential of full-scale phosphorus recovery by struvite precipitation · Cranfield
Checking a claim in this area?
We can run the same search on any method or claim. If nothing turns up, we will say so, and that proves nothing on its own.