The influence of four parameters (temperature, scavenging time, amount of scavenger, and concentration of palladium in the solution) on the efficiency of Pd removal from a cross-coupling reaction, using a commercially available Pd scavenger, SPM32, was studied. The DoE-based method employed yielded more information than is readily attainable from standard adsorption isotherms and kinetics experiments. The optimal regime of scavenging was identified; intuitive and nonintuitive effects of temperature, scavenging time, and scavenger amounts were highlighted; and a mathematical model quantifying predicted Pd removal from the synthetic intermediate was built.

This series of texts has been designed for students on courses in horticulture at the Higher National Certificate or Diploma level, but care has been taken to ensure that they are neither too specialised for lower-level courses, nor too superficial for university work. All the contributors to the series have had experience in both the horticultural industry and education. Consequently, the books have a strong practical flavour which should reinforce their value as textbooks and also make them of interest to a wide audience, including growers and farmers, extension officers, research workers and workers in the agrochemical, marketing and allied industries, and the many gardeners who are interested in the science behind their hobby.

Dispersion corrected density functional theory (DFT-D) has been applied to understand the performance of several palladium metal scavengers. Nine different sulfur-based ligands and three different palladium metal sets have been investigated in detail. Based on a thorough analysis of the thermodynamic binding parameters ΔH, ΔG and ΔS, we have identified the best binding modes for all scavenger ligands. Bis-monodentate coordination is favoured over chelation in ΔH and ΔG values for most of the scavenger ligands. Special attention has been paid to the ligand strain energies, which account for the structural changes of the ligands upon complexation indicating that small (5-membered) chelates are considerably less favourable than expected. Some ligands can use their longest chain (>7-atoms) to yield trans chelates, which ligands with shorter chains (≤6-atoms) are unable to form. A secondary amino nitrogen (RR'NH) is found to be the best donor with highest binding enthalpy for Pd(ii) metal systems. In terms of the strength of the initial binding interactions, -SMe > -SH; capping thiols (-SH) as thioethers (-SMe) is therefore suggested to be an effective strategy in scavenger design. These observations mark the beginning of a knowledge base of the full range of possible interactions, leading to the construction of a sulfur ligand database for the design of scavenger systems.

Acanthopanax senticosus extract with excessive standard of Pb, Cd, Hg, and Cu was used as the research object, and the alkyl thiourea functionalised silica was used as a new heavy metal removal scavenger. The heavy metal removal process was optimised by orthogonal experiment with dynamic and static adsorption modes. Meanwhile, the content of Acanthopanax B and Acanthopanax E, the solid content, and the HPLC fingerprint similarity were used as quality monitoring indicators of Acanthopanax senticosus heavy metal removal before and after. Then, the technical adaptability of heavy metal removal by alkyl thiourea functionalised silica was evaluated. Under the optimal dynamic adsorption conditions, the average removal rates of Pb, Cd, Hg, and Cu were 91.64%, 93.04%, 81.77%, and 83.11%, respectively. Under the optimal static adsorption conditions, the average removal rates of Pb, Cd, Hg, and Cu were 82.22%, 89.95%, 81.26%, and 82.97%, respectively. During Acanthopanax senticosus extract heavy metal removal before and after, the change percentage of Acanthopanax B and Acanthopanax E was less than 2.00%, the solid content loss rate was only 0.18%, and the fingerprint similarity was over 99.9%. The method can be used to satisfy the high efficiency of selective removal of harmful elements in Acanthopanax senticosus extract and the effective composition of almost no effect; the method is simple and easy, so it can be recommended for pretreatment of heavy metals in Traditional Chinese Medicine extracts, and this way provides a new thought and research technique to decrease the contents of heavy metals.

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