Optimality of Commercial Resins and Functionalized Chitosan Derivatives for the Recovery and Reuse of Pd(ll) from Synthetic Electroless Plating Solutions

Optimality of commercial resins and functionalized chitosan derivatives for the recovery and reuse of Pd(II) from synthetic.

Department of Chemical Engineering Indian Institute of Technology Guwahati

Their guidance greatly assisted my needs during the term of my research and thesis writing. In addition to my advisors, I would like to esteemed doctoral committee members of my thesis, namely prof.

Srinu Nagireddi ([email protected])

Introduction and Literature Review 1-36

Experimental, Analytical and Modelling Methodologies 37-50

Pd(II) speciation studies of synthetic ELP solutions 40

Chapter 3: Pd(II) Speciation Characteristics of Synthetic ELP Solutions and Adsorptive Efficacy of Raw Chitosan

Pd(II) speciation characteristics of synthetic ELP solutions 52 3.3 Solubility resistance based optimality of solution pH 53
Pd(II) adsorption characteristics of chitosan-ELP solution system 54 .1 Effect of adsorption parameters on Pd(II) adsorption 54

Efficacy of Commercial Resins for Pd(II) Removal, Recovery and Reuse

Equilibrium, kinetic and thermodynamic model fitness 78
Batch desorption characteristics of commercial resins 87
Summary 90

Chapter 5: Pd(II) Adsorption and Desorption Characteristics of Nitrogen Functionalized Chitosan Derivatives

Solubility resistance of CH-ME and CH-TETA derivatives 94 5.3 Pd(II) adsorption characteristics of CH-ME and CH-TETA derivatives 94
Surface characterizations of raw and Pd(II) loaded derivatives 106

Chapter 6: Pd(II) Adsorption and Desorption Characteristics of Sulfur and Nitrogen Functionalized Chitosan Derivatives

Solubility resistance of CH-TSC and CH−AZ derivatives 116 6.3 Pd(II) adsorption characteristics of CH-TSC and CH-AZ derivatives 116
Efficacy of alternate resins based on Pd(II) adsorption and desorption characteristics and cost indices

Fig.6.1: Effect of initial solution pH on Pd(II) adsorption characteristics of (a) CH-TSC and (b) CH-AZ derivatives. Fig.6.2: Effect of adsorbent dose on Pd(II) adsorption characteristics of (a) CH-TSC and (b) CH-AZ derivatives.

Notations

Introduction and Literature Review

Preamble

Need for Pd(II) recovery and reuse
Technologies for Pd(II) recovery from waste streams
Prominence of adsorptive ion-exchange technologies
Overview of Pd(II) adsorption systems
Adsorptive materials for Pd(II) recovery
Targeted perspectives

Continuous and ever-increasing demand for the rare earth metals is emphasized after recovery and reuse of Pd(II) from used sources such as used catalysts, industrial waste streams, etc. of Pd(II) in acidic media and. In this regard, despite good adsorption properties, commercial physisorbents such as activated carbon have been proven to be ineffective due to poor desorption properties (Rajesh 2014).

Prior art

Pd(II) speciation in acidic and chloride adsorbate systems
Effect of pH and chloride concentration variation on Pd(II) uptake
Functional groups chemistry associated to Pd(II) uptake of synthetic and commercial resins
Adsorption and desorption studies using commercial ion-exchange resins
Pd(II) adsorption and desorption characteristics of chitosan and its derivatives
Pd(II) adsorption and desorption characteristics of other chelating resins
Cost effectiveness and ranking of Pd(II) adsorptive chelating resins

Ding et al., (2006) investigated the adsorption properties of two types of diaza-crown ether cross-linked chitosan resins for Pd(II) and Ag(I) recovery. Sharma et al., (2016) synthesized Aliquat-336 (ionic liquid) impregnated SBA-15 mesoporous silica for Pd(II) adsorption.

Possible scope for further research

Pd(II) speciation characteristics for complex adsorbate systems
Pd(II) adsorption and desorption characteristics of various adsorbents and complex adsorbate systems
Role of eluents on desorption characteristics
Identification of cost effective adsorbents for Pd(II) recovery from complex adsorbate systems

In this regard, the adsorption efficiency of S-, N- and O-functionalized derivatives may be worth considering for Pd(II) recovery from complex solutions. Based on HSAB, chitosan and its functionalized and commercial derivatives can be investigated to evaluate their efficiency and competence in recovering Pd(II) from complex adsorbate systems such as ELP solutions. Therefore, it is necessary to evaluate the cost-effectiveness of adsorbents for Pd(II) recovery from both simple and complex adsorbate systems.

Objectives of the thesis

Such insights are much needed to constrain and assign economic competitiveness-based benchmarks for the identification of low-cost adsorbents and methods to further reduce the retail cost of manufacturing most competent resins.

Organization of the thesis

Materials

Palladium stock solution precursors
Other chemicals
Commercial resins
Preparation of palladium stock solution

Pd(II) speciation studies of synthetic ELP solutions
Synthesis of chitosan derivatives

Chitosan-Epichlorohydrin derivative
Chitosan-Melamine (CH-ME) derivative
Chitosan-Triethylenetetramine (CH-TETA) derivative
Chitosan-Thiosemicarbazide (CH-TSC) derivative

Solubility studies for chitosan and its derivatives
Surface characterization
Batch adsorption studies
Batch desorption experiments

Batch desorption of Pd(II) loaded chitosan
Batch desorption of Pd(II) loaded commercial resins
Batch desorption of Pd(II) loaded chitosan derivatives

Fitness of equilibrium, kinetic and thermodynamic models

Equilibrium models
Kinetic models
Thermodynamic model

Then, the chapter also presents a brief overview of research directions for future research in the field of recovery and reuse of precious metals from complex adsorption systems. Considering such spent solutions and reused spent solutions, the concentrations of Pd(II) solution in this work were varied in the range of 50–300 mg L-1. The metal recovery for reuse was evaluated using a mass balance of the Pd(II) concentration in the solution before and after desorption.

Pd(II) Speciation Characteristics of Synthetic ELP Solutions and Adsorptive

Pd(II) Speciation Characteristics of Synthetic ELP Solutions and Adsorptive Efficacy of Raw Chitosan

Introduction
Pd(II) speciation characteristics of synthetic ELP solutions
Solubility resistance based optimality of solution pH
Pd(II) adsorption characteristics of chitosan-ELP solution system

Effect of adsorption parameters on Pd(II) adsorption
Effect of CTAB on Pd(II) uptake
Equilibrium, kinetic and thermodynamic model parameters

Characterization of chitosan adsorbent

Surface area analysis
Thermogravimetric analysis
Crystallinity analysis
FTIR spectra

The increase in Pd(II) removal efficiency with adsorbent dosage was due to the increase in the number of active sites available for Pd(II) adsorption. The Pd(II) adsorption characteristics of the chitosan-ELP system with respect to the contact time are shown in Figs. Thus, it is clear that the results obtained in this work are comparable to those reported in the literature and the complexity of the solution did not have a strong influence on the Pd(II) adsorption characteristics of the chitosan-ELP system.

Wavenumber (cm -1 )

CHNS analysis
EDX spectra
Pd(II) desorption characteristics of chitosan
Summary

The FESEM spectra of chitosan obtained before and after Pd(II) adsorption have been depicted in Fig. It can also be seen that the chitosan surface became smooth after Pd(II) adsorption from synthetic ELP solutions (Fig. 3.9a and 3.9c). . The inclusion of CTAB as an additive in the synthetic ELP solutions marginally improved the adsorption properties and contributed to a contributing role of CTAB surfactant in influencing the Pd(II) adsorption properties.

Efficacy of Commercial Resins for Pd(II) Removal, Recovery and Reuse

Efficacy of Commercial Resins for Pd(II) Removal, Recovery, and Reuse

Introduction
Batch adsorption characteristics
Equilibrium, kinetic and thermodynamic model fitness
Characterization of commercial resins

FTIR spectra

Based on adsorption studies performed at certain combinations of contact time (720 min), adsorbent dosage (1 g L-1) and initial Pd(II) concentration (50 mg L-1), Figures 4.1a–4.1c show the optimum pH plot , related to Pd(II) adsorption on Amberlyst A21, Amberlite IRA 958 and Dowex MSA, respectively. Based on adsorption studies performed for certain combinations of pH (4 for Dowex MSA and Amberlite IRA 958 and 2 for Amberlyst A21), contact time (720 min) and initial Pd(II) concentration (50 mg L-1), Fig. 4.2a–4.2c show the adsorbent dose optimality curves associated with the adsorption of Pd(II) on Amberlyst A21, Amberlite IRA 958 and Dowex MSA, respectively. The influence of Pd(II) concentration (50-300 mg L-1) and temperature (298-333 K) on Pd(II) adsorption properties of commercial resins is shown in Fig.

Wavenumber (cm-1)

EDX spectra
Batch desorption characteristics of commercial resins
Efficacy of commercial resins
Summary

In this regard, it is interesting to note that nitrogen functional groups containing commercial resins (Dowex MSA) performed better than resins (in terms of adsorption and desorption capacity) with sulfur and sulfur-nitrogen functional groups (LewatitTP214). Fifth, among four commercial resins (three commercial resins considered in this paper and one previously studied resin) containing functional groups containing S-N/N/N-O, with significant adsorption and desorption characteristic (65-70% removal) , it can be concluded that Dowex MSA is the best adsorbent for the studied application. Finally, when cost-effectiveness is considered, among the four commercial resins (containing N or N-O or S-N functional groups), Amberlyst A21 is proven to be the most effective, despite showing poorer absorption kinetics and adsorption capacity.

Pd(II) Adsorption and Desorption Characteristics of Nitrogen Functionalized

Pd(II) Adsorption and Desorption Characteristics of Nitrogen Functionalized Chitosan Derivatives

Background

Surface characterizations were performed using Fourier Transform-Infrared Spectrophotometer (FTIR), Braummer-Emmet-Teller (BET), X-ray diffractometer (XRD), Thermo Gravimetric Analyzer (TGA) and field emission scanning microscopy equipped energy dispersive X-ray analyzer (FESEM-EDX). For optimized pH, adsorbent dosage and contact time, adsorption experiments were performed for a wider range of Pd(II) solution concentrations (50–300 mg L-1). The specific influence of different additives such as Na2EDTA (stabilizer) and ammonia (NH3) on the Pd(II) adsorption characteristics of nitrogen functionalized chitosan derivatives was investigated.

Solubility resistance of CH-ME and CH-TETA derivatives

Pd(II) adsorption characteristics of CH-ME and CH-TETA derivatives

Effect of adsorption parameters on batch adsorption characteristics

Based on this hypothesis, it can be concluded that Pd(II) adsorption on CH-ME and CH-TETA derivatives is most likely to occur due to electrostatic attraction and ion exchange in the ELP solutions, where the electrostatic interaction takes place between them. These experiments were performed at pH 2, 1.8 and 1 g L-1 dosing of CH-ME and CH-TETA derivatives, respectively, along with an initial Pd(II) concentration of 50 mg L-1. The illustrated figures and table confirm the best suitability of Freundlich and Langmuir models for CH-ME and CH-TETA derivatives, respectively, to represent measured batch equilibrium data.

Desorption characteristics of Pd(II) loaded CH-ME and CH-TETA derivatives

The experimental results regarding optimality of adsorption parameters, adsorption and desorption properties of CH-ME and CH-TETA derivatives have been compared with the best available literature for most relevant adsorbate (electroless plating solutions) and adsorbent. However, the CH-ME derivative was marginally poor with respect to glutaraldehyde cross-linked chitosan (104.17 mg g-1 for 50-300 mg L-1 initial Pd(II) solution concentration range compared to 166.67 mg g-1 for 50 - 500 mg L-1 initial Pd(II) solution concentration range). Therefore, the performance of CH-ME and CH-TETA derivatives is comparable to glutaraldehyde cross-linked chitosan resin for both adsorption and desorption properties.

Surface characterizations of raw and Pd(II) loaded derivatives

FTIR spectra
EDX spectra

The interactions of Pd(II) ions with primary amine groups in the structure of CH-TETA were confirmed by the shift in the peak from 3436 to 3293 cm-1. Similar patterns were obtained for the case of a CH-TETA derivative as shown in Fig. The Pd(II) loaded CH-TETA sample confirmed the existence of a significant amount of Pd (5.5%) on the adsorbent surface (Fig. 5.11d).

Summary

Second, the Pd(II) desorption properties are 39.68 and 59.82% for CH-TETA and CH-ME, respectively. The higher contact time and better Pd(II) desorption properties of CH-ME can be targeted by appropriate variation in functional group chemistry facilitated by stoichiometric and synthesis changes. From the perspective of Pd(II) recovery and recycling, compared to glutaraldehyde-crosslinked chitosan performance, CH-ME performed better but not CH-TETA.

Pd(II) Adsorption and Desorption Characteristics of Sulfur and Nitrogen

Pd(II) Adsorption and Desorption Characteristics of Sulfur and Nitrogen Functionalized Chitosan

Derivatives

Introduction

Considering these limitations, Pd(II) adsorption and desorption characteristics were focused on CH-TSC and CH-AZ derivatives with synthetic ELP solutions.

Solubility resistance of CH-TSC and CH−AZ derivatives

Pd(II) adsorption characteristics of CH-TSC and CH-AZ derivatives

Effect of adsorption parameters on batch adsorption characteristics

The optimality of the adsorbent dosage in relation to the Pd(II) adsorption characteristics of the CH−TSC and CH−AZ and ELP system is illustrated in Fig. For the data reported, an initial solution pH of 2 and 4 for CH-TSC and CH-Az was used, respectively. Compared to chitosan, higher removal efficiency was achieved for CH-TSC and CH-AZ derivatives.

Desorption characteristics of Pd(II) loaded CH-TSC and CH-AZ derivatives

However, the desorption efficiency is significantly poor compared to commercial resins, namely Lewatit TP214, Amberlite IRA958 and Dowex Marathon MSA, whose desorption efficiency values are high and approximately 66%. Thus, it can be concluded that both CH-TSC and CH-AZ are satisfactory but not excellent resins for Pd(II) recovery and reuse from synthetic ELP solutions. d) The comparison with other literature is not relevant because it concerns aqueous media and solutions without any chemical complexity. However, a good influence is that better adsorption capacity was obtained for CH-TSC and CH-AZ when comparing with thiourea-modified chitosan microspheres (112.4 mg g-1).

Surface characterization of raw and Pd(II) loaded resins

FTIR analysis
FESEM and EDX analysis

The shift of the peaks seen in the range of wave numbers from 3436 to 3293 cm-1 confirms the interaction of Pd species with the primary amine groups of the CH−AZ structure (Figure 6.7c). NH– (Zhong et al. 2010), thus concluding that CH-TSC was successful. The peak shift seen in the wavenumber range from 3436 to 3293 cm-1 for Pd-loaded CH-TSC (Figure 6.8c) confirms the interaction of Pd species with the primary amine groups of the CH-TSC structure.

Efficacy of alternate resins based on Pd(II) adsorption and desorption characteristics and cost indices

The given data are interesting from the point of view of performance indices and costs, which are very lacking in the available literature. First, the efficiency index based on the adsorption of alternative materials is similar with the maximum value obtained for the CH-AZ derivative. Amberlyst A21, followed by Amberlite IRA 958, performed best in all indices, including cost indices for Pd(II) removal and recovery from synthetic ELP solutions.

Summary

Conclusions and Future Work

Conclusions

Speciation analysis in ELP solutions
Performance characteristics of raw chitosan
Pd(II) adsorption and desorption characteristics of commercial resins
Pd(II) adsorption and desorption characteristics of nitrogen functionalized chitosan based derivatives
Pd(II) adsorption and desorption characteristics of nitrogen and sulfur functionalized chitosan based derivatives

Thermodynamic evaluations showed that Pd(II) adsorption is spontaneous and exothermic for both resins. The data from the BET surface area analysis are not very synergistic with the adsorption and desorption characteristics of Pd(II). In summary, the adsorption and desorption characteristics of Pd(II) cannot be fully understood from surface characterization analyses.

Future work

Development of super-efficient chelating resins with enhanced noble metal desorption characteristics based on chelation chemistry and functional groups. Detailed cost analysis of all resins reported so far for their cost-effectiveness towards noble metal recovery from spent and chemically complex waste adsorption systems of solution variants. Research the commercialization and technology transfer of competitive higher cost adsorbents for the recovery and reuse of noble metals from real waste streams and adsorption systems.